#INFOSWMM

Markdown – Storm Water Management Model User’s Manual Version 5

– –

United States
Environmental Protection
Agency
EPA/600/R - 14/4 13b
Revised September 2015
www2.epa.gov/ water-research

Storm Water Management Model

User’s Manual Version 5.

Office of Research and Development
Water Supply and Water Resources Division
EPA- 600 /R-14/413b
Revisied September 2015
Storm Water Management Model User’s Manual Version 5. by
Lewis A. Rossman
Envronmental Scientist, Emeritus
U.S. Environmental Protection Agency
National Risk Management
Laboratory Office of Research and
Development U.S. Environmental
Protection Agency 26 Martin Luther
King Drive Cincinnati, OH 45268
September 2015
ii

ACKNOWLEDGEMENTS

This manual was prepared by Lewis A. Rossman, Environmental Scientist Emeritus, U.S.
Environmental Protection Agency, Office of Research and Development, National Risk
Management Research Laboratory.
iii

DISCLAIMER

The information in this document has been funded wholly or in part by the U.S. Environmental
Protection Agency (EPA). It has been subjected to the Agency’s peer and administrative review,
and has been approved for publication as an EPA document. Note that approval does not signify
that the contents necessarily reflect the views of the Agency. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use. NOTICE: This report was prepared as an account of work sponsored by an agency of the United
States Government. Neither the United States Government, nor any agency thereof, nor any of
their employees, nor any of their contractors, subcontractors, or their employees, make any
warranty, express or implied, or assume any legal liability or responsibility for the accuracy,
completeness, or usefulness of any information, apparatus, product, or process disclosed, or
represent that its use would not infringe privately owned rights. Reference herein to any specific
commercial product, process, or service by trade name, trademark, manufacturer, or otherwise,
does not necessarily constitute or imply its endorsement, recommendation, or favoring by the
United States Government, any agency thereof, or any of their contractors or subcontractors. The
views and opinions expressed herein do not necessarily state or reflect those of the United States
Government, any agency thereof, or any of their contractors.

iv

CONTENTS

ACKNOWLEDGEMENTS ………………………………………………………………………………………………… II

x
  • CHAPTER 1 – INTRODUCTION DISCLAIMER III
  • 1.1 What is SWMM
  • 1.2 Modeling Capabilities
  • 1.3 Typical Applications of SWMM
  • 1.4 Installing EPA SWMM
  • 1.5 Steps in Using SWMM
  • 1.6 About This Manual
  • CHAPTER 2 – QUICK START TUTORIAL
  • 2.1 Example Study Area
  • 2.2 Project Setup
  • 2.3 Drawing Objects
  • 2.4 Setting Object Properties
  • 2.5 Running a Simulation
  • 2.6 Simulating Water Quality
  • 2.7 Running a Continuous Simulation
  • CHAPTER 3 – SWMM’S CONCEPTUAL MODEL
  • 3.1 Introduction
  • 3.2 Visual Objects
  • 3.3 Non-Visual Objects
  • 3.4 Computational Methods
  • CHAPTER 4 – SWMM’S MAIN WINDOW
  • 4.1 Overview
  • 4.2 Main Menu
  • 4.3 Toolbars v
  • 4.4 Status Bar
  • 4.5 Study Area Map
  • 4.6 Project Browser
  • 4.7 Map Browser……………………………………………………………………………………………………..
  • 4.8 Property Editor
  • 4.9 Setting Program Preferences
  • CHAPTER 5 – WORKING WITH PROJECTS
  • 5.1 Creating a New Project
  • 5.2 Opening an Existing Project
  • 5.3 Saving a Project
  • 5.4 Setting Project Defaults
  • 5.5 Measurement Units
  • 5.6 Link Offset Conventions
  • 5.7 Calibration Data
  • 5.8 Viewing All Project Data
  • CHAPTER 6 – WORKING WITH OBJECTS
  • 6.1 Types of Objects
  • 6.2 Adding Objects
  • 6.3 Selecting and Moving Objects
  • 6.4 Editing Objects
  • 6.5 Converting an Object
  • 6.6 Copying and Pasting Objects
  • 6.7 Shaping and Reversing Links
  • 6.8 Shaping a Subcatchment
  • 6.9 Deleting an Object
  • 6.10 Editing or Deleting a Group of Objects
  • CHAPTER 7 – WORKING WITH THE MAP vi
  • 7.1 Selecting a Map Theme
  • 7.2 Setting the Map’s Dimensions
  • 7.3 Utilizing a Backdrop Image
  • 7.4 Measuring Distances
  • 7.5 Zooming the Map
  • 7.6 Panning the Map
  • 7.7 Viewing at Full Extent
  • 7.8 Finding an Object
  • 7.9 Submitting a Map Query
  • 7.10 Using the Map Legends
  • 7.11 Using the Overview Map
  • 7.12 Setting Map Display Options
  • 7.13 Exporting the Map
  • CHAPTER 8 – RUNNING A SIMULATION
  • 8.1 Setting Simulation Options
  • 8.2 Setting Reporting Options
  • 8.3 Starting a Simulation
  • 8.4 Troubleshooting Results
  • CHAPTER 9 – VIEWING RESULTS
  • 9.1 Viewing a Status Report
  • 9.2 Viewing Summary Results
  • 9.3 Time Series Results
  • 9.4 Viewing Results on the Map
  • 9.5 Viewing Results with a Graph…………………………………………………………………………….
  • 9.6 Customizing a Graph’s Appearance
  • 9.7 Viewing Results with a Table
  • 9.8 Viewing a Statistics Report vii
  • CHAPTER 10 – PRINTING AND COPYING
  • 10.1 Selecting a Printer
  • 10.2 Setting the Page Format
  • 10.3 Print Preview…………………………………………………………………………………………………….
  • 10.4 Printing the Current View
  • 10.5 Copying to the Clipboard or to a File
  • CHAPTER 11 – FILES USED BY SWMM
  • 11.1 Project Files
  • 11.2 Report and Output Files
  • 11.3 Rainfall Files
  • 11.4 Climate Files
  • 11.5 Calibration Files
  • 11.6 Time Series Files
  • 11.7 Interface Files
  • CHAPTER 12 – USING ADD-IN TOOLS
  • 12.1 What Are Add-In Tools
  • 12.2 Configuring Add-In Tools
  • APPENDIX A – USEFUL TABLES
  • A.1 Units of Measurement
  • A.2 Soil Characteristics
  • A.3 NRCS Hydrologic Soil Group Definitions
  • A.4 SCS Curve Numbers
  • A.5 Depression Storage
  • A.6 Manning’s n – Overland Flow
  • A.7 Manning’s n – Closed Conduits
  • A.8 Manning’s n – Open Channels
  • A.9 Water Quality Characteristics of Urban Runoff viii
  • A.10 Culvert Code Numbers
  • A.11 Culvert Entrance Loss Coefficients
  • A.12 Standard Elliptical Pipe Sizes
  • A.13 Standard Arch Pipe Sizes
  • APPENDIX B – VISUAL OBJECT PROPERTIES
  • B.1 Rain Gage Properties
  • B.2 Subcatchment Properties
  • B.3 Junction Properties
  • B.4 Outfall Properties
  • B.5 Flow Divider Properties
  • B.6 Storage Unit Properties
  • B.7 Conduit Properties
  • B.8 Pump Properties
  • B.9 Orifice Properties
  • B.10 Weir Properties
  • B.11 Outlet Properties
  • B.12 Map Label Properties
  • APPENDIX C – SPECIALIZED PROPERTY EDITORS
  • C.1 Aquifer Editor
  • C.2 Climatology Editor
  • C.3 Control Rules Editor
  • C.4 Cross-Section Editor
  • C.5 Curve Editor
  • C.6 Groundwater Flow Editor
  • C.7 Groundwater Equation Editor
  • C.8 Infiltration Editor
  • C.9 Inflows Editor ix
  • C.10 Initial Buildup Editor
  • C.11 Land Use Editor
  • C.12 Land Use Assignment Editor
  • C.13 LID Control Editor
  • C.14 LID Group Editor
  • C.15 LID Usage Editor
  • C.16 Pollutant Editor
  • C.17 Snow Pack Editor
  • C.18 Time Pattern Editor
  • C.19 Time Series Editor
  • C.20 Title/Notes Editor
  • C.21 Transect Editor
  • C.22 Treatment Editor
  • C.23 Unit Hydrograph Editor
  • APPENDIX D – COMMAND LINE SWMM
  • APPENDIX E – ERROR AND WARNING MESSAGES
  • FIGURE 2-1 EXAMPLE STUDY AREA LIST OF FIGURES
  • FIGURE 2-2 DEFAULT ID LABELING FOR TUTORIAL EXAMPLE
  • FIGURE 2-3 MAP OPTIONS DIALOG
  • FIGURE 2-4 SUBCATCHMENTS AND NODES FOR EXAMPLE STUDY AREA
  • FIGURE 2-5 PROPERTY EDITOR WINDOW
  • FIGURE 2-6 GROUP EDITOR DIALOG
  • FIGURE 2-7 TIME SERIES EDITOR
  • FIGURE 2-8 TITLE/NOTES EDITOR
  • FIGURE 2-9 SIMULATION OPTIONS DIALOG
  • FIGURE 2- 10 PORTION OF A STATUS REPORT
  • FIGURE 2- 11 NODE FLOODING SUMMARY TABLE
  • FIGURE 2- 12 CONDUIT SURCHARGE SUMMARY TABLE
  • FIGURE 2- 13 VIEWING COLOR-CODED RESULTS ON THE STUDY ARE A MAP
  • FIGURE 2- 14 TIME SERIES PLOT DIALOGS
  • FIGURE 2- 15 TIME SERIES PLOT OF LINK FLOWS
  • FIGURE 2- 16 PROFILE PLOT DIALOG
  • FIGURE 2- 17 EXAMPLE PROFILE PLOT
  • FIGURE 2- 18 DYNAMIC W AVE SIMULATION OPTIONS
  • FIGURE 2- 19 POLLUTANT EDITOR DIALOG
  • FIGURE 2- 20 LAND USE EDITOR DIALOG
  • FIGURE 2- 21 DEFINING A TSS BUILDUP FUNCTION
  • FIGURE 2- 22 LAND USE ASSIGNMENT DIALOG
  • FIGURE 2- 23 RUNOFF TSS FROM SELECTED SUBCATCHMENTS
  • FIGURE 2- 24 STATISTICS SELECTION DIALOG
  • FIGURE 2- 25 EXAMPLE STATISTICS REPORT
  • FIGURE 3-1 PHYSICAL OBJECTS USED TO MODEL A DRAINAGE SYSTEM
  • FIGURE 3-2 CONCRETE BOX CULVERT
  • FIGURE 3-3 AREAL DEPLETION CURVE FOR A NATURAL AREA
  • FIGURE 3-4 AN RDII UNIT HYDROGRAPH
  • FIGURE 3-5 EXAMPLE OF A NATURAL CHANNEL TRANSECT
  • FIGURE 3-6 ADJUSTMENT OF SUBCATCHMENT PARAMETERS AFTER LID PLACEMENT
  • FIGURE 3-7 CONCEPTUAL VIEW OF SURFACE RUNOFF xi
  • FIGURE 3-8 TWO-ZONE GROUNDWATER MODEL
  • FIGURE 3-9 CONCEPTUAL DIAGRAM OF A BIO-RETENTION CELL LID
  • FIGURE 8-1 FLOW INSTABILITY INDEX FOR A FLOW HYDROGRAPH
  • FIGURE 11-1 COMBINING ROUTING INTERFACE FILES
  • TABLE 3-1 AV AILABLE CROSS SECTION SHAPES FOR CONDUITS LIST OF TABLES
  • TABLE 3-2 AVAILABLE TYPES OF WEIRS
  • TABLE 9-1 TIME SERIES VARIABLES AVAILABLE FOR VIEWING
  • TABLE D-1 GEOMETRIC PARAMETERS OF CONDUIT CROSS SECTIONS
  • TABLE D-2 POLLUTANT BUILDUP FUNCTIONS (T IS ANTECEDENT DRY DAYS)
  • TABLE D-3 POLLUTANT WASH OFF FUNCTIONS

CHAPTER 1 – INTRODUCTION

1.1 What is SWMM

The EPA Storm Water Management Model (SWMM) is a dynamic rainfall-runoff simulation model
used for single event or long-term (continuous) simulation of runoff quantity and quality from
primarily urban areas. The runoff component of SWMM operates on a collection of subcatchment
areas that receive precipitation and generate runoff and pollutant loads. The routing portion of
SWMM transports this runoff through a system of pipes, channels, storage/treatment devices,
pumps, and regulators. SWMM tracks the quantity and quality of runoff generated within each
subcatchment, and the flow rate, flow depth, and quality of water in each pipe and channel during
a simulation period comprised of multiple time steps. SWMM was first developed in 1971^1 and has undergone several major upgrades since then^2. It
continues to be widely used throughout the world for planning, analysis and design related to
storm water runoff, combined sewers, sanitary sewers, and other drainage systems in urban (^1) Metcalf & Eddy, Inc., University of Florida, Water Resources Engineers, Inc. “Storm Water
Management Model, Volume I – Final Report”, 11024DOC07/71, Water Quality Office,
Environmental Protection Agency, Washington, DC, July 1971.
(^2) Huber, W.C. and Dickinson, R.E., “Storm Water Management Model, Version 4: User’s Manual,
EPA/600/3-88/001a, Environmental Research Laboratory, U.S. Environmental Protection Agency,
Athens, GA, October 1992. areas, with many applications in non-urban areas as well. The current edition, Version 5, is a
complete re-write of the previous release. Running under Windows, SWMM 5 provides an integrated environment for editing study area
input data, running hydrologic, hydraulic and water quality simulations, and viewing the results in
a variety of formats. These include color-coded drainage area and conveyance system maps,
time series graphs and tables, profile plots, and statistical frequency analyses. This latest re-write of SWMM was produced by the Water Supply and Water Resources Division
of the U.S. Environmental Protection Agency’s National Risk Management Research Laboratory
with assistance from the consulting firm of CDM-Smith.

1.2 Modeling Capabilities

SWMM accounts for various hydrologic processes that produce runoff from urban areas. These
include:
 time-varying rainfall
 evaporation of standing surface water
 snow accumulation and melting
 rainfall interception from depression storage
 infiltration of rainfall into unsaturated soil layers
 percolation of infiltrated water into groundwater layers
 interflow between groundwater and the drainage system
 nonlinear reservoir routing of overland flow
 capture and retention of rainfall/runoff with various types of low impact development (LID)
practices. Spatial variability in all of these processes is achieved by dividing a study area into a collection of
smaller, homogeneous subcatchment areas, each containing its own fraction of pervious and
impervious sub-areas. Overland flow can be routed between sub-areas, between subcatchments,
or between entry points of a drainage system. SWMM also contains a flexible set of hydraulic modeling capabilities used to route runoff and
external inflows through a drainage system network of pipes, channels, storage/treatment units
and diversion structures. These include the ability to:
 handle networks of unlimited size
 use a wide variety of standard closed and open conduit shapes as well as natural
channels
 model special elements such as storage/treatment units, flow dividers, pumps, weirs, and
orifices
 apply external flows and water quality inputs from surface runoff, groundwater interflow,
rainfall-dependent infiltration/inflow, dry weather sanitary flow, and user-defined inflows
 utilize either kinematic wave or full dynamic wave flow routing methods
 model various flow regimes, such as backwater, surcharging, reverse flow, and surface
ponding
 apply user-defined dynamic control rules to simulate the operation of pumps, orifice
openings, and weir crest levels.
In addition to modeling the generation and transport of runoff flows, SWMM can also estimate the
production of pollutant loads associated with this runoff. The following processes can be modeled
for any number of user-defined water quality constituents:
 dry-weather pollutant buildup over different land uses
 pollutant washoff from specific land uses during storm events
 direct contribution of rainfall deposition
 reduction in dry-weather buildup due to street cleaning
 reduction in washoff load due to BMPs
 entry of dry weather sanitary flows and user-specified external inflows at any point in the
drainage system
 routing of water quality constituents through the drainage system
 reduction in constituent concentration through treatment in storage units or by natural
processes in pipes and channels.

1.3 Typical Applications of SWMM

Since its inception, SWMM has been used in thousands of sewer and stormwater studies
throughout the world. Typical applications include:
 design and sizing of drainage system components for flood control
 sizing of detention facilities and their appurtenances for flood control and water quality
protection
 flood plain mapping of natural channel systems
 designing control strategies for minimizing combined sewer overflows
 evaluating the impact of inflow and infiltration on sanitary sewer overflows
 generating non-point source pollutant loadings for waste load allocation studies
 evaluating the effectiveness of BMPs for reducing wet weather pollutant loadings.

1.4 Installing EPA SWMM

EPA SWMM Version 5 is designed to run under all versions of the Microsoft Windows personal
computer operating system. It is distributed as a single file, swmm51xxx_setup.exe (where xxx is
the current release number which as of this writing is 010) that contains a self-extracting setup
program. To install EPA SWMM:
  1. Select Run from the Windows Start menu.
  2. Enter the full path and name of the setup file or click the Browse button to locate it on
    your computer.
  3. Click the OK button type to begin the setup process.
The setup program will ask you to choose a folder (directory) where the SWMM program files will
be placed. The default folder is c:\Program Files\EPA SWMM 5.1. After the files are installed
your Start Menu will have a new item named EPA SWMM 5.1. To launch SWMM, simply select this item off of the Start Menu, and then select EPA SWMM 5.1 from the submenu that appears.
(The name of the executable file that runs SWMM under Windows is epaswmm5.exe.) A user’s personal settings for running SWMM are stored in a folder named EPASWMM under the
user’s Application Data directory (e.g., Users\AppData\Roaming\EPASWMM for
Windows 7). If you need to save these settings to a different location, you can install a shortcut to
SWMM 5 on the desktop whose target entry includes the name of the SWMM 5 executable
followed by /s , where is the name of the folder where the personal
settings will be stored. An example might be:
“c:\Program Files\EPA SWMM 5.1\ epaswmm5.exe” /s “My Folders\SWMM5\”.
Several example data sets have been included with the installation package to help users
become familiar with the program. They are placed in a sub-folder named EPA SWMM
Projects\Examples in the user’s My Documents folder. Each example consists of a .INP file that
holds the project’s data along with a .TXT file that describes the system being modeled. To remove EPA SWMM from your computer, do the following:
  1. Select Settings from the Windows Start menu.
  2. Select Control Panel from the Settings menu.
  3. Double-click on the Add/Remove Programs item.
  4. Select EPA SWMM 5.1 from the list of programs that appears.
  5. Click the Add/Remove button.

1.5 Steps in Using SWMM

One typically carries out the following steps when using EPA SWMM to model a study area:
  1. Specify a default set of options and object properties to use (see Section 5.4).
  2. Draw a network representation of the physical components of the study area (see Section
    6.2).
  3. Edit the properties of the objects that make up the system (see Section 6.4).
  4. Select a set of analysis options (see Section 8.1).
  5. Run a simulation (see Section 8.2).
  6. View the results of the simulation (see Chapter 9).
For building larger systems from scratch it will be more convenient to replace Step 2 by collecting
study area data from various sources, such as CAD drawings or GIS files, and transferring these
data into a SWMM input file whose format is described in Appendix D of this manual.

1.6 About This Manual

Chapter 2 presents a short tutorial to help get started using EPA SWMM. It shows how to add
objects to a SWMM project, how to edit the properties of these objects, how to run a single event
simulation for both hydrology and water quality, and how to run a long-term continuous
simulation. Chapter 3 provides background material on how SWMM models stormwater runoff within a
drainage area. It discusses the behavior of the physical components that comprise a stormwater
drainage area and collection system as well as how additional modeling information, such as
rainfall quantity, dry weather sanitary inflows, and operational control, are handled. It also
provides an overview of how the numerical simulation of system hydrology, hydraulics and water
quality behavior is carried out. Chapter 4 shows how the EPA SWMM graphical user interface is organized. It describes the
functions of the various menu options and toolbar buttons, and how the three main windows – the
Study Area Map, the Browser panel, and the Property Editor—are used. Chapter 5 discusses the project files that store all of the information contained in a SWMM model
of a drainage system. It shows how to create, open, and save these files as well as how to set
default project options. It also discusses how to register calibration data that are used to compare
simulation results against actual measurements. Chapter 6 describes how one goes about building a network model of a drainage system with
SWMM. It shows how to create the various physical objects (subcatchment areas, drainage pipes
and channels, pumps, weirs, storage units, etc.) that make up a system, how to edit the
properties of these objects, and how to describe the way that externally imposed inflows,
boundary conditions and operational controls change over time. Chapter 7 explains how to use the study area map that provides a graphical view of the system
being modeled. It shows how to view different design and computed parameters in color-coded
fashion on the map, how to re-scale, zoom, and pan the map, how to locate objects on the map,
how to utilize a backdrop image, and what options are available to customize the appearance of
the map. Chapter 8 shows how to run a simulation of a SWMM model. It describes the various options that
control how the analysis is made and offers some troubleshooting tips to use when examining
simulation results. Chapter 9 discusses the various ways in which the results of an analysis can be viewed. These
include different views of the study area map, various kinds of graphs and tables, and several
different types of special reports. Chapter 10 explains how to print and copy the results discussed in Chapter 9. Chapter 11 describes how EPA SWMM can use different types of interface files to make
simulations runs more efficient. Chapter 12 describes how add-in tools can be registered and share data with SWMM. These
tools are external applications launched from SWMM’s graphical user interface that can extend its
capabilities. The manual also contains several appendixes: Appendix A – provides several useful tables of parameter values, including a table of units of
expression for all design and computed parameters. Appendix B – lists the editable properties of all visual objects that can be displayed on the
study area map and be selected for editing using point and click. Appendix C – describes the specialized editors available for setting the properties of non-visual
objects. Appendix D – provides instructions for running the command line version of SWMM and
includes a detailed description of the format of a project file. Appendix E – lists all of the error messages and their meaning that SWMM can produce.

CHAPTER 2 – QUICK START TUTORIAL

This chapter provides a tutorial on how to use EPA SWMM. If you are not familiar with the
elements that comprise a drainage system, and how these are represented in a SWMM model,
you might want to review the material in Chapter 3 first.

2.1 Example Study Area

In this tutorial we will model the drainage system serving a 12-acre residential area. The system
layout is shown in Figure 2-1 and consists of subcatchment areas^3 S1 through S3, storm sewer
conduits C1 through C4, and conduit junctions J1 through J4. The system discharges to a creek
at the point labeled Out1. We will first go through the steps of creating the objects shown in this
diagram on SWMM’s study area map and setting the various properties of these objects. Then we
will simulate the water quantity and quality response to a 3-inch, 6-hour rainfall event, as well as a
continuous, multi-year rainfall record.
Figure 2-1 Example study area

2.2 Project Setup

Our first task is to create a new SWMM project and make sure that certain default options are
selected. Using these defaults will simplify the data entry tasks later on.
  1. Launch EPA SWMM if it is not already running and select File >> New from the Main
    Menu bar to create a new project.
  2. Select Project >> Defaults to open the Project Defaults dialog.
(^3) A subcatchment is an area of land containing a mix of pervious and impervious surfaces whose
runoff drains to a common outlet point, which could be either a node of the drainage network or
another subcatchment.
  1. On the ID Labels page of the dialog, set the ID Prefixes as shown in Figure 2-2. This will
    make SWMM automatically label new objects with consecutive numbers following the
    designated prefix.

FIGURE 2-2 DEFAULT ID LABELING FOR TUTORIAL EXAMPLE

  1. On the Subcatchments page of the dialog set the following default values:
    Area 4
    Width 400
    % Slope 0.
    % Imperv. 50
    N- Imperv. 0.
    N- Perv. 0.
    Dstore-Imperv. 0.
    Dstore-Perv 0.
    %Zero-Imperv. 25
    Infil. Model
    • Method Modified Green-Ampt
    • Suction Head 3.
    • Conductivity 0.
    • Initial Deficit 0.
  2. On the Nodes/Links page set the following default values:
    Node Invert 0
    Node Max. Depth 4
    Node Ponded Area 0
    Conduit Length 400
    Conduit Geometry
    • Barrels 1
    • Shape Circular
    • Max. Depth 1.0
      Conduit Roughness 0.01
      Flow Units CFS
      Link Offsets DEPTH
      Routing Model Kinematic Wave
  3. Click OK to accept these choices and close the dialog. If you wanted to save these
    choices for all future new projects you could check the Save box at the bottom of the form
    before accepting it.
Next we will set some map display options so that ID labels and symbols will be displayed as we
add objects to the study area map, and links will have direction arrows.
  1. Select Tools >> Map Display Options to bring up the Map Options dialog (see Figure 2-
    3).
  2. Select the Subcatchments page, set the Fill Style to Diagonal and the Symbol Size to 5.
  3. Then select the Nodes page and set the Node Size to 5.
  4. Select the Annotation page and check off the boxes that will display ID labels for
    Subcatchments, Nodes, and Links. Leave the others un-checked.
  5. Finally, select the Flow Arrows page, select the Filled arrow style, and set the arrow size
    to 7.
  6. Click the OK button to accept these choices and close the dialog.

FIGURE 2-3 MAP OPTIONS DIALOG

Before placing objects on the map we should set its dimensions.
  1. Select View >> Dimensions to bring up the Map Dimensions dialog.
  2. You can leave the dimensions at their default values for this example.
Finally, look in the status bar at the bottom of the main window and check that the Auto-Length
feature is off.

2.3 Drawing Objects

We are now ready to begin adding components to the Study Area Map^4. We will start with the
subcatchments.
  1. Begin by selecting the Subcatchments category (under Hydrology) in the Project
    Browser panel (on the left side of the main window).
(^4) Drawing objects on the map is just one way of creating a project. For large projects it might be
more convenient to first construct a SWMM project file external to the program. The project file is
a text file that describes each object in a specified format as described in Appendix D of this
manual. Data extracted from various sources, such as CAD drawings or GIS files, can be used to
create the project file.
  1. Then click the button on the toolbar underneath the object category listing in the
    Project panel (or select Project | Add a New Subcatchment from the main menu).
    Notice how the mouse cursor changes shape to a pencil when you move it over the map.
  2. Move the mouse to the map location where one of the corners of subcatchment S1 lies
    and left-click the mouse.
  3. Do the same for the next three corners and then right-click the mouse (or hit the Enter
    key) to close up the rectangle that represents subcatchment S1. You can press the Esc
    key if instead you wanted to cancel your partially drawn subcatchment and start over
    again. Don’t worry if the shape or position of the object isn’t quite right. We will go back
    later and show how to fix this.
  4. Repeat this process for subcatchments S2 and S3^5.
Observe how sequential ID labels are generated automatically as we add objects to the map. Next we will add in the junction nodes and the outfall node that comprise part of the drainage
network.
  1. To begin adding junctions, select the Junctions category from the Project Browser
    (under Hydraulics -> Nodes) and click the button or select Project | Add a New
    Junction from the main menu..
  2. Move the mouse to the position of junction J1 and left-click it. Do the same for junctions
    J2 t hrough J4.
  3. To add the outfall node, select Outfalls from the Project Browser, click the button or
    select Project | Add a New Outfall from the main menu, move the mouse to the outfall’s
    location on the map, and left-click. Note how the outfall was automatically given the name
    Out1.
At this point your map should look something like that shown in Figure 2-4.

FIGURE 2-4 SUBCATCHMENTS AND NODES FOR EXAMPLE STUDY AREA

(^5) If you right-click (or press Enter) after adding the first point of a subcatchment’s outline, the
subcatchment will be shown as just a single point. Now we will add the storm sewer conduits that connect our drainage system nodes to one
another. (You must have created a link’s end nodes as described previously before you can
create the link.) We will begin with conduit C1, which connects junction J1 to J2.
  1. Select the Conduits from the Project Browser (under Hydraulics -> Links) and press the
    button or select Project | Add a New Conduit from the main menu. The mouse
    cursor will change shape to a cross hair when moved onto the map.
  2. Left-c lick the mouse on junction J1. Note how the mouse cursor changes shape to a
    pencil.
  3. Move the mouse over to junction J2 (note how an outline of the conduit is drawn as you
    move the mouse) and left-click to create the conduit. You could have cancelled the
    operation by either right clicking or by hitting the key.
  4. Repeat this procedure for conduits C2 through C4.
Although all of our conduits were drawn as straight lines, it is possible to draw a curved link by
left-clicking at intermediate points where the direction of the link changes before clicking on the
end node. To complete the construction of our study area schematic we need to add a rain gage.
  1. Select the Rain Gages category from the Project Browser panel (under Hydrology) and
    either click the button or select Project | Add a New Rain Gage from the main menu.
  2. Move the mouse over the Study Area Map to where the gage should be located and left-
    click the mouse.
At this point we have completed drawing the example study area. Your system should look like
the one in Figure 2-1. If a rain gage, subcatchment or node is out of position you can move it by
doing the following:
  1. If the button on the Map Toolbar is not already depressed, click it to place the map in
    Object Selection mode.
  2. Click on the object to be moved.
  3. Drag the object with the left mouse button held down to its new position.
To re-shape a subcatchment’s outline:
  1. With the map in Object Selection mode, click on the subcatchment’s centroid (indicated
    by a solid square within the subcatchment) to select it.
  2. Then click the button on the Map Toolbar to put the map into Vertex Selection mode.
  3. Select a vertex point on the subcatchment outline by clicking on it (note how the selected
    vertex is indicated by a filled solid square).
  4. Drag the vertex to its new position with the left mouse button held down.
  5. If need be, vertices can be added or deleted from the outline by right-clicking the mouse
    and selecting the appropriate option from the popup menu that appears.
  6. When finished, click the button to return to Object Selection mode.
This same procedure can also be used to re-shape a link.

2.4 Setting Object Properties

As visual objects are added to our project, SWMM assigns them a default set of properties. To
change the value of a specific property for an object we must select the object into the Property
Editor (see Figure 2-5). There are several different ways to do this. If the Editor is already visible,
then you can simply click on the object or select it from the Project Browser. If the Editor is not
visible then you can make it appear by one of the following actions:
 double-click the object on the map,
 or right-click on the object and select Properties from the pop-up menu that appears,
 or select the object from the Project Browser and then click the Browser’s button.

FIGURE 2-5 PROPERTY EDITOR WINDOW

Whenever the Property Editor has the focus you can press the F1 key to obtain a more detailed
description of the properties listed. Two key properties of our subcatchments that need to be set are the rain gage that supplies
rainfall data to the subcatchment and the node of the drainage system that receives runoff from the subcatchment. Since all of our subcatchments utilize the same rain gage, Gage1, we can use
a shortcut method to set this property for all subcatchments at once:
  1. From the main menu select Edit >>Select All.
  2. Then select Edit >> Group Edit to make a Group Editor dialog appear (see Figure 2-6).
  3. Select Subcatchment as the type of object to edit, Rain Gage as the property to edit, and
    type in Gage1 as the new value.
  4. Click OK to change the rain gage of all subcatchments to Gage1. A confirmation dialog
    will appear noting that 3 subcatchments have changed. Select “No” when asked to
    continue editing.

FIGURE 2-6 GROUP EDITOR DIALOG

To set the outlet node of our subcatchments we have to proceed one by one, since these vary by
subcatchment:
  1. Double click on subcatchment S1 or select it from the Project Browser and click the
    Browser’s button to bring up the Property Editor.
  2. Type J1 in the Outlet field and press Enter. Note how a dotted line is drawn between the
    subcatchment and the node.
  3. Click on subcatchment S2 and enter J2 as its Outlet.
  4. Click on subcatchment S3 and enter J3 as its Outlet.
We also wish to represent area S3 as being less developed than the others. Select S3 into the
Property Editor and set its % Imperviousness to 25. The junctions and outfall of our drainage system need to have invert elevations assigned to them.
As we did with the subcatchments, select each junction individually into the Property Editor and
set its Invert Elevation to the value shown below6.
Node Invert
J1 96
J2 90
J3 93
J4 88
Out1 85
Only one of the conduits in our example system has a non-default property value. This is conduit
C4, the outlet pipe, whose diameter should be 1.5 instead of 1 ft. To change its diameter, select
conduit C4 into the Property Editor and set the Max. Depth value to 1.5. In order to provide a source of rainfall input to our project we need to set the rain gage’s
properties. Select Gage1 into the Property Editor and set the following properties:
Rain Format INTENSITY
Rain Interval 1:00
Data Source TIMESERIES
Series Name TS1
As mentioned earlier, we want to simulate the response of our study area to a 3-inch, 6-hour
design storm. A time series named TS1 will contain the hourly rainfall intensities that make up this
storm. Thus we need to create a time series object and populate it with data. To do this:
  1. From the Project Browser select the Time Series category of objects.
  2. Click the button on the Browser to bring up the Time Series Editor dialog (see Figure
    2-7).
  3. Enter TS1 in the Time Series Name field.
  4. Enter the values shown in Figure 2-7 into the Time and Value columns of the data entry
    grid (leave the Date column blank).
  5. You can click the View button on the dialog to see a graph of the time series values.
    Click the OK button to accept the new time series.
7
8
(^6) An alternative way to move from one object of a given type to the next in order (or to the
previous one) in the Property Editor is to hit the Page Down (or Page Up) key.
(^7) The Time Series Editor can also be launched directly from the Rain Gage Property Editor by
selecting the editor’s Series Name field and double clicking on it.
(^8) Leaving off the dates for a time series means that SWMM will interpret the time values as hours
from the start of the simulation. Otherwise, the time series follows the date/time values specified
by the user.

FIGURE 2-7 TIME SERIES EDITOR

Having completed the initial design of our example project it is a good idea to give it a title and
save our work to a file at this point. To do this:
  1. Select the Title/Notes category from the Project Browser and click the button.
  2. In the Project Title/Notes dialog that appears (see Figure 2-8), enter “Tutorial Example”
    as the title of our project and click the OK button to close the dialog.
  3. From the File menu select the Save As option.
  4. In the Save As dialog that appears, select a folder and file name under which to save this
    project. We suggest naming the file tutorial.inp. (An extension of .inp will be added to
    the file name if one is not supplied.)
  5. Click Save to save the project to file.

FIGURE 2-8 TITLE/NOTES EDITOR

The project data are saved to the file in a readable text format. You can view what the file looks
like by selecting Project >> Details from the main menu. To open our project at some later time,
you would select the Open command from the File menu.

2.5 Running a Simulation

Setting Simulation Options Before analyzing the performance of our example drainage system we need to set some options
that determine how the analysis will be carried out. To do this:
  1. From the Project Browser, select the Options category and click the button.
  2. On the General page of the Simulation Options dialog that appears (see Figure 2-9),
    select Kinematic Wave as the flow routing method. The infiltration method should
    already be set to Modified Green-Ampt. The Allow Ponding option should be
    unchecked.
  3. On the Dates page of the dialog, set the End Analysis time to 12:00:00.
  4. On the Time Steps page, set the Routing Time Step to 60 seconds.
  5. Click OK to close the Simulation Options dialog.

FIGURE 2-9 SIMULATION OPTIONS DIALOG

Starting a Simulation We are now ready to run the simulation. To do so, select Project >> Run Simulation (or click the button). If there was a problem with the simulation, a Status Report will appear describing
what errors occurred. Upon successfully completing a run, there are numerous ways in which to
view the results of the simulation. We will illustrate just a few here. Viewing the Status Report The Status Report contains useful information about the quality of a simulation run, including a
mass balance on rainfall, infiltration, evaporation, runoff, and inflow/outflow for the conveyance system. To view the report select Report >> Status (or click the button on the Standard
Toolbar and then select Status Report from the drop down menu). A portion of the report for the
system just analyzed is shown in Figure 2-10.
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.1 (Build 5.1.010)
--------------------------------------------------------------
Tutorial Example
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
RDII ................... NO
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... MODIFIED_GREEN_AMPT
Flow Routing Method ...... KINWAVE
Starting Date ............ JUN-27- 2002 00:00:00
Ending Date .............. JUN-27- 2002 12:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:15:00
Wet Time Step ............ 00:15:00
Dry Time Step ............ 01:00:00
Routing Time Step ........ 60.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 3.000 3.000
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 1.750 1.750
Surface Runoff ........... 1.246 1.246
Final Storage ............ 0.016 0.016
Continuity Error (%) ..... -0.386
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 1.246 0.406
Groundwater Inflow ....... 0.000 0.000

FIGURE 2- 10 PORTION OF A STATUS REPORT

For the system we just analyzed the report indicates the quality of the simulation is quite good,
with negligible mass balance continuity errors for both runoff and routing (-0.39% and 0. 03 %, respectively, if all data were entered correctly). Also, of the 3 inches of rain that fell on the study
area, 1.75 infiltrated into the ground and essentially the remainder became runoff. Viewing the Summary Report The Summary Report contains tables listing summary results for each subcatchment, node and
link in the drainage system. Total rainfall, total runoff, and peak runoff for each subcatchment,
peak depth and hours flooded for each node, and peak flow, velocity, and depth for each conduit
are just some of the outcomes included in the summary report. To view the Summary Report select Report | Summary from the main menu (or click the
button on the Standard Toolbar and then select Summary Report from the drop down menu).
The report’s window has a drop down list from which you select a particular report to view. For
our example, the Node Flooding Summary table (Figure 2-11) indicates there was internal
flooding in the system at node J2. Note. The Conduit Surcharge Summary table (Figure 2-12)
shows that Conduit C2, just downstream of node J2, was at full capacity and therefore appears to
be slightly undersized. In SWMM flooding will occur whenever the water surface at a node exceeds the maximum
assigned depth. Normally such water will be lost from the system. The option also exists to have
this water pond atop the node and be re-introduced into the drainage system when capacity
exists to do so.

FIGURE 2- 11 NODE FLOODING SUMMARY TABLE

FIGURE 2- 12 CONDUIT SURCHARGE SUMMARY TABLE

Viewing Results on the Map Simulation results (as well as some design parameters, such as subcatchment area, node invert
elevation, and link maximum depth) can be viewed in color-coded fashion on the study area map.
To view a particular variable in this fashion:
  1. Select the Map page of the Browser panel.
  2. Select the variables to view for Subcatchments, Nodes, and Links from the dropdown
    combo boxes appearing in the Themes panel. In Figure 2-13, subcatchment runoff and
    link flow have been selected for viewing.

FIGURE 2- 13 VIEWING COLOR-CODED RESULTS ON THE STUDY ARE A MAP

  1. The color-coding used for a particular variable is displayed with a legend on the study
    area map. To toggle the display of a legend, select View >> Legends.
  2. To move a legend to another location, drag it with the left mouse button held down.
  3. To change the color-coding and the breakpoint values for different colors, select View >>
    Legends >> Modify and then the pertinent class of object (or if the legend is already
    visible, simply right-click on it). To view numerical values for the variables being displayed
    on the map, select Tools >> Map Display Options and then select the Annotation page
    of the Map Options dialog. Use the check boxes for Subcatchment Values, Node Values,
    and Link Values to specify what kind of annotation to add.
  4. The Date / Time of Day / Elapsed Time controls on the Map Browser can be used to
    move through the simulation results in time. Figure 2-13 depicts results at 5 hours and 45
    minutes into the simulation.
  5. You can use the controls in the Animator panel of the Map Browser (see Figure 2-13) to
    animate the map display through time. For example, pressing the button will run the
    animation forward in time.
Viewing a Time Series Plot To generate a time series plot of a simulation result:
  1. Select Report >> Graph >> Time Series or simply click on the Standard Toolbar.
  2. A Time Series Plot Selection dialog will appear. It is used to select the objects and
    variables to be plotted.
For our example, the Time Series Plot Selection dialog can be used to graph the flow in conduits
C1 and C2 as follows (refer to Figure 2-14a):
  1. Click the Add button on the dialog to view the Data Series Selection dialog (Figure 2-
    14(b).
  2. Select conduit C1 (either on the map or in the Project Browser) and select Flow as the
    variable to be plotted. Click the Accept button to return to the Time Series Plot Selection
    dialog.
  3. Repeat steps 1 and 2 for conduit C2.
  4. Press OK to create the plot which should look like the graph in Figure 2-15.
(a) (b)

FIGURE 2- 14 TIME SERIES PLOT DIALOGS

FIGURE 2- 15 TIME SERIES PLOT OF LINK FLOWS

After a plot is created you can:
 customize its appearance by selecting Report >> Customize or by clicking the
button on the Standard Toolbar or by simply right clicking on the plot,
 copy it to the clipboard and paste it into another application by selecting Edit >> Copy To
or clicking on the Standard Toolbar
 print it by selecting File >> Print or File >> Print Preview (use File >> Page Setup first
to set margins, orientation, etc.).
Viewing a Profile Plot SWMM can generate profile plots showing how water surface depth varies across a path of
connected nodes and links. Let’s create such a plot for the conduits connecting junction J1 to the
outfall Out1 of our example drainage system. To do this:
  1. Select Report >> Graph >> Profile on the main menu or simply click on the Standard
    Toolbar.
  2. Either enter J1 in the Start Node field of the Profile Plot Selection dialog that appears
    (see Figure 2-16) or select it on the map or from the Project Browser and click the
    button next to the field.

FIGURE 2- 16 PROFILE PLOT DIALOG

  1. Do the same for node Out1 in the End Node field of the dialog.
  2. Click the Find Path button. An ordered list of the links forming a connected path between
    the specified Start and End nodes will be displayed in the Links in Profile box. You can
    edit the entries in this box if need be.
  3. Click the OK button to create the plot, showing the water surface profile as it exists at the
    simulation time currently selected in the Map Browser (see Figure 2-17 for hour 02:45).

FIGURE 2- 17 EXAMPLE PROFILE PLOT

As you move through time using the Map Browser or with the Animator control, the water depth
profile on the plot will be updated. Observe how node J2 becomes flooded between hours 2 and
3 of the storm event. A Profile Plot’s appearance can be customized and it can be copied or
printed using the same procedures as for a Time Series Plot. Running a Full Dynamic Wave Analysis In the analysis just run we chose to use the Kinematic Wave method of routing flows through our
drainage system. This is an efficient but simplified approach that cannot deal with such
phenomena as backwater effects, pressurized flow, flow reversal, and non-dendritic layouts.
SWMM also includes a Dynamic Wave routing procedure that can represent these conditions.
This procedure, however, requires more computation time, due to the need for smaller time steps
to maintain numerical stability. Most of the effects mentioned above would not apply to our example. However we had one
conduit, C2, which flowed full and caused its upstream junction to flood. It could be that this pipe
is actually being pressurized and could therefore convey more flow than was computed using
Kinematic Wave routing. We would now like to see what would happen if we apply Dynamic
Wave routing instead. To run the analysis with Dynamic Wave routing:
  1. From the Project Browser, select the Options category and click the button.
  2. On the General page of the Simulation Options dialog that appears, select Dynamic
    Wave as the flow routing method.
  3. On the Dynamic Wave page of the dialog, use the settings shown in Figure 2-18.
    9

FIGURE 2- 18 DYNAMIC W AVE SIMULATION OPTIONS

(^9) Normally when running a Dynamic Wave analysis, one would also want to reduce the routing
time step (on the Time Steps page of the dialog). We will keep it at 60 seconds.
  1. Click OK to close the form and select Project >> Run Simulation (or click the
    button) to re-run the analysis.
If you look at the Summary Report for this run, you will see that there is no longer any junction
flooding and that the peak flow carried by conduit C2 has been increased from 3. 52 cfs to 4.04
cfs.

2.6 Simulating Water Quality

In the next phase of this tutorial we will add water quality analysis to our example project. SWMM
has the ability to analyze the buildup, washoff, transport and treatment of any number of water
quality constituents. The steps needed to accomplish this are:
  1. Identify the pollutants to be analyzed.
  2. Define the categories of land uses that generate these pollutants.
  3. Set the parameters of buildup and washoff functions that determine the quality of runoff
    from each land use.
  4. Assign a mixture of land uses to each subcatchment area
  5. Define pollutant removal functions for nodes within the drainage system that contain
    treatment facilities.
We will now apply each of these steps, with the exception of number 5, to our example project^10. We will define two runoff pollutants; total suspended solids (TSS), measured as mg/L, and total
Lead, measured in ug/L. In addition, we will specify that the concentration of Lead in runoff is a
fixed fraction (0.25) of the TSS concentration. To add these pollutants to our project:
  1. Under the Quality category in the project Browser, select the Pollutants sub-category
    beneath it.
  2. Click the button to add a new pollutant to the project.
  3. In the Pollutant Editor dialog that appears (see Figure 2-19), enter TSS for the pollutant
    name and leave the other data fields at their default settings.
  4. Click the OK button to close the Editor.
  5. Click the button on the Project Browser again to add our next pollutant.
  6. In the Pollutant Editor, enter Lead for the pollutant name, select UG/L for the
    concentration units, enter TSS as the name of the Co-Pollutant, and enter 0.25 as the
    Co-Fraction value.
(^10) Aside from surface runoff, SWMM also allows pollutants to be introduced into the nodes of a
drainage system through user-defined time series of direct inflows, dry weather inflows,
groundwater interflow, and rainfall dependent inflow/infiltration
  1. Click the OK button to close the Editor.
In SWMM, pollutants associated with runoff are generated by specific land uses assigned to
subcatchments. In our example, we will define two categories of land uses: Residential and
Undeveloped. To add these land uses to the project:
  1. Under the Quality category in the Project Browser, select the Land Uses sub-category
    and click the button.
  2. In the Land Use Editor dialog that appears (see Figure 2-20), enter Residential in the
    Name field and then click the OK button.
  3. Repeat steps 1 and 2 to create the Undeveloped land use category.

FIGURE 2- 19 POLLUTANT EDITOR DIALOG

Next we need to define buildup and washoff functions for TSS in each of our land use categories.
Functions for Lead are not needed since its runoff concentration was defined to be a fixed fraction
of the TSS concentration. Normally, defining these functions requires site-specific calibration. In this example we will assume that suspended solids in Residential areas builds up at a constant
rate of 1 pound per acre per day until a limit of 50 lbs per acre is reached. For the Undeveloped area we will assume that buildup is only half as much. For the washoff function, we will assume a
constant event mean concentration of 100 mg/L for Residential land and 50 mg/L for
Undeveloped land. When runoff occurs, these concentrations will be maintained until the
available buildup is exhausted. To define these functions for the Residential land use:
  1. Select the Residential land use category from the Project Browser and click the
    button.
  2. In the Land Use Editor dialog, move to the Buildup page (see Figure 2-21).
  3. Select TSS as the pollutant and POW (for Power function) as the function type.
  4. Assign the function a maximum buildup of 50 , a rate constant of 1.0, a power of 1 and
    select AREA as the normalizer.
  5. Move to the Washoff page of the dialog and select TSS as the pollutant, EMC as the
    function type, and enter 100 for the coefficient. Fill the other fields with 0.
  6. Click the OK button to accept your entries.
Now do the same for the Undeveloped land use category, except use a maximum buildup of 25 , a
buildup rate constant of 0.5, a buildup power of 1 , and a washoff EMC of 50.

FIGURE 2- 21 DEFINING A TSS BUILDUP FUNCTION

The final step in our water quality example is to assign a mixture of land uses to each
subcatchment area:
  1. Select subcatchment S1 into the Property Editor.
  2. Select the Land Uses property and click the ellipsis button (or press Enter).
  3. In the Land Use Assignment dialog that appears, enter 75 for the % Residential and 25
    for the % Undeveloped (see Figure 2-22). Then click the OK button to close the dialog.

FIGURE 2- 22 LAND USE ASSIGNMENT DIALOG

  1. Repeat the same three steps for subcatchment S2.
  2. Repeat the same for subcatchment S3, except assign the land uses as 25% Residential
    and 75% Undeveloped.
Before we simulate the runoff quantities of TSS and Lead from our study area, an initial buildup of
TSS should be defined so it can be washed off during our single rainfall event. We can either
specify the number of antecedent dry days prior to the simulation or directly specify the initial
buildup mass on each subcatchment. We will use the former method:
  1. From the Options category of the Project Browser, select the Dates sub-category and
    click the button.
  2. In the Simulation Options dialog that appears, enter 5 into the Antecedent Dry Days
    field.
  3. Leave the other simulation options the same as they were for the dynamic wave flow
    routing we just completed.
  4. Click the OK button to close the dialog.
Now run the simulation by selecting Project >> Run Simulation or by clicking on the
Standard Toolbar. When the run is completed, view its Status Report. Note that two new sections have been added
for Runoff Quality Continuity and Quality Routing Continuity. From the Runoff Quality Continuity table we see that there was an initial buildup of 47.5 lbs of TSS on the study area and
an additional 2.2 lbs of buildup added during the dry periods of the simulation. About 47.9 lbs
were washed off during the rainfall event. The quantity of Lead washed off is a fixed percentage
(25% times 0.001 to convert from mg to ug) of the TSS as was specified. If you plot the runoff concentration of TSS for subcatchment S1 and S3 together on the same
time series graph, as in Figure 2-23, you will see the difference in concentrations resulting from
the different mix of land uses in these two areas. You can also see that the duration over which
pollutants are washed off is much shorter than the duration of the entire runoff hydrograph (i.e., 1
hour versus about 6 hours). This results from having exhausted the available buildup of TSS over
this period of time.

FIGURE 2- 23 RUNOFF TSS FROM SELECTED SUBCATCHMENTS

2.7 Running a Continuous Simulation

As a final exercise in this tutorial we will demonstrate how to run a long-term continuous
simulation using a historical rainfall record and how to perform a statistical frequency analysis on
the results. The rainfall record will come from a file named sta310301.dat that was included with
the example data sets provided with EPA SWMM. It contains several years of hourly rainfall
beginning in January 1998. The data are stored in the National Climatic Data Center’s DSI 3240
format, which SWMM can automatically recognize. To run a continuous simulation with this rainfall record:
  1. Select the rain gage Gage1 into the Property Editor.
  2. Change the selection of Data Source to FILE.
  3. Select the File Name data field and click the ellipsis button (or press the Enter key) to
    bring up a standard Windows File Selection dialog.
  4. Navigate to the folder where the SWMM example files were stored, select the file named
    sta310301.dat, and click Open to select the file and close the dialog.
  5. In the Station No. field of the Property Editor enter 310301.
  6. Select the Options category in the Project Browser and click the button to bring up
    the Simulation Options form.
  7. On the General page of the form, select Kinematic Wave as the Routing Method (this
    will help speed up the computations).
  8. On the Dates page of the form, set both the Start Analysis and Start Reporting dates to
    01/01/1998, and set the End Analysis date to 01/01/2000.
  9. On the Time Steps page of the form, set the Routing Time Step to 300 seconds.
  10. Close the Simulation Options form by clicking the OK button and start the simulation by
    selecting Project >> Run Simulation (or by clicking on the Standard Toolbar).
After our continuous simulation is completed we can perform a statistical frequency analysis on
any of the variables produced as output. For example, to determine the distribution of rainfall
volumes within each storm event over the two-year period simulated:
  1. Select Report >> Statistics or click the button on the Standard Toolbar.
  2. In the Statistics Selection dialog that appears, enter the values shown in Figure 2-24.
  3. Click the OK button to close the form.

FIGURE 2- 24 STATISTICS SELECTION DIALOG

The results of this request will be a Statistics Report form (see Figure 2-25) containing four
tabbed pages: a Summary page, an Events page containing a rank-ordered listing of each event,
a Histogram page containing a plot of the occurrence frequency versus event magnitude, and a
Frequency Plot page that plots event magnitude versus cumulative frequency. The summary page shows that there were a total of 213 rainfall events. The Events page shows
that the largest rainfall event had a volume of 3.35 inches and occurred over a 24- hour period.
There were no events that matched the 3-inch, 6-hour design storm event used in our previous
single-event analysis that had produced some internal flooding. In fact, the Summary R eport for
this continuous simulation indicates that there were no flooding or surcharge occurrences over
the simulation period.

FIGURE 2- 25 EXAMPLE STATISTICS REPORT

We have only touched the surface of SWMM’s capabilities. Some additional features of the
program that you will find useful include:
 utilizing additional types of drainage elements, such as storage units, flow dividers,
pumps, and regulators, to model more complex types of systems
 using control rules to simulate real-time operation of pumps and regulators
 employing different types of externally-imposed inflows at drainage system nodes, such
as direct time series inflows, dry weather inflows, and rainfall-derived infiltration/inflow
 modeling groundwater interflow between aquifers beneath subcatchment areas and
drainage system nodes
 modeling snow fall accumulation and melting within subcatchments
 adding calibration data to a project so that simulated results can be compared with
measured values
 utilizing a background street, site plan, or topo map to assist in laying out a system's
drainage elements and to help relate simulated results to real-world locations.
You can find more information on these and other features in the remaining chapters of this
manual.

CHAPTER 3 – SWMM’S CONCEPTUAL MODEL

This chapter discusses how SWMM models the objects and operational parameters that
constitute a stormwater drainage system. Details about how this information is entered into the
program are presented in later chapters. An overview is also given on the computational methods
that SWMM uses to simulate the hydrology, hydraulics and water quality behavior of a drainage
system.

3.1 Introduction

SWMM conceptualizes a drainage system as a series of water and material flows between
several major environmental compartments. These compartments and the SWMM objects they
contain include:
 The Atmosphere compartment, which generates precipitation and deposits pollutants
onto the land surface compartment. SWMM uses Rain Gage objects to represent rainfall
inputs to the system.
 The Land Surface compartment, which is represented through one or more
Subcatchment objects. It receives precipitation from the Atmospheric compartment in the
form of rain or snow; it sends outflow in the form of infiltration to the Groundwater
compartment and also as surface runoff and pollutant loadings to the Transport
compartment.
 The Groundwater compartment receives infiltration from the Land Surface compartment
and transfers a portion of this inflow to the Transport compartment. This compartment is
modeled using Aquifer objects.
 The Transport compartment contains a network of conveyance elements (channels,
pipes, pumps, and regulators) and storage/treatment units that transport water to outfalls
or to treatment facilities. Inflows to this compartment can come from surface runoff,
groundwater interflow, sanitary dry weather flow, or from user-defined hydrographs. The
components of the Transport compartment are modeled with Node and Link objects
Not all compartments need appear in a particular SWMM model. For example, one could model
just the transport compartment, using pre-defined hydrographs as inputs.

3.2 Visual Objects

Figure 3-1 depicts how a collection of SWMM’s visual objects might be arranged together to
represent a stormwater drainage system. These objects can be displayed on a map in the SWMM
workspace. The following sections describe each of these objects.

FIGURE 3-1 PHYSICAL OBJECTS USED TO MODEL A DRAINAGE SYSTEM

3.2.1 Rain Gages Rain Gages supply precipitation data for one or more subcatchment areas in a study region. The
rainfall data can be either a user-defined time series or come from an external file. Several
different popular rainfall file formats currently in use are supported, as well as a standard user-
defined format. More details on these formats are presented in Section 11.3. The principal input properties of rain gages include:
 rainfall data type (e.g., intensity, volume, or cumulative volume)
 recording time interval (e.g., hourly, 15-minute, etc.)
 source of rainfall data (input time series or external file)
 name of rainfall data source
3.2.2 Subcatchments Subcatchments are hydrologic units of land whose topography and drainage system elements
direct surface runoff to a single discharge point. The user is responsible for dividing a study area
into an appropriate number of subcatchments, and for identifying the outlet point of each
subcatchment. Discharge outlet points can be either nodes of the drainage system or other
subcatchments. Subcatchments are divided into pervious and impervious subareas. Surface runoff can infiltrate
into the upper soil zone of the pervious subarea, but not through the impervious subarea.
Impervious areas are themselves divided into two subareas – one that contains depression
storage and another that does not. Runoff flow from one subarea in a subcatchment can be
routed to the other subarea, or both subareas can drain to the subcatchment outlet. Infiltration of rainfall from the pervious area of a subcatchment into the unsaturated upper soil
zone can be described using four different models:
 Horton infiltration
 Modified Horton infiltration
 Green-Ampt infiltration
 Modified Green-Ampt infiltration
 Curve Number infiltration
To model the accumulation, re-distribution, and melting of precipitation that falls as snow on a
subcatchment, it must be assigned a Snow Pack object. To model groundwater flow between an
aquifer underneath the subcatchment and a node of the drainage system, the subcatchment must
be assigned a set of Groundwater parameters. Pollutant buildup and washoff from
subcatchments are associated with the Land Uses assigned to the subcatchment. Capture and
retention of rainfall/runoff using different types of low impact development practices (such as bio-
retention cells, infiltration trenches, porous pavement, vegetative swales, and rain barrels) can be
modeled by assigning a set of pre-designed LID controls to the subcatchment. The other principal input parameters for subcatchments include:
 assigned rain gage
 outlet node or subcatchment
 assigned land uses
 tributary surface area
 imperviousness
 slope
 characteristic width of overland flow
 Manning's n for overland flow on both pervious and impervious areas
 depression storage in both pervious and impervious areas
 percent of impervious area with no depression storage.
3.2.3 Junction Nodes Junctions are drainage system nodes where links join together. Physically they can represent the
confluence of natural surface channels, manholes in a sewer system, or pipe connection fittings.
External inflows can enter the system at junctions. Excess water at a junction can become
partially pressurized while connecting conduits are surcharged and can either be lost from the
system or be allowed to pond atop the junction and subsequently drain back into the junction. The principal input parameters for a junction are:
 invert (channel or manhole bottom) elevation
 height to ground surface
 ponded surface area when flooded (optional)
 external inflow data (optional).
3.2.4 Outfall Nodes Outfalls are terminal nodes of the drainage system used to define final downstream boundaries
under Dynamic Wave flow routing. For other types of flow routing they behave as a junction. Only
a single link can be connected to an outfall node, and the option exists to have the outfall
discharge onto a subcatchment’s surface. The boundary conditions at an outfall can be described by any one of the following stage
relationships:
 the critical or normal flow depth in the connecting conduit
 a fixed stage elevation
 a tidal stage described in a table of tide height versus hour of the day
 a user-defined time series of stage versus time.
The principal input parameters for outfalls include:
 invert elevation
 boundary condition type and stage description
 presence of a flap gate to prevent backflow through the outfall.
3.2.5 Flow Divider Nodes Flow Dividers are drainage system nodes that divert inflows to a specific conduit in a prescribed
manner. A flow divider can have no more than two conduit links on its discharge side. Flow
dividers are only active under Steady Flow and Kinematic Wave routing and are treated as simple
junctions under Dynamic Wave routing. There are four types of flow dividers, defined by the manner in which inflows are diverted:
Cutoff Divider: diverts all inflow above a defined cutoff value.
Overflow Divider: diverts all inflow above the flow capacity of the non-diverted
conduit.
Tabular Divider: (^) uses a table that expresses diverted flow as a function of total
inflow.
Weir Divider: uses a weir equation to compute diverted flow.
The flow diverted through a weir divider is computed by the following equation
)( 5.1
div=CQ fHww where Qdiv = diverted flow, Cw = weir coefficient, Hw = weir height and f is computed as
max min
min
QQ
QQ
f in
−
−
=
where Qin is the inflow to the divider, Qmin is the flow at which diversion begins, and . The user-specified parameters for the weir divider are Qmin, Hw, and Cw.
The principal input parameters for a flow divider are:
5.1
max= HCQ ww
 junction parameters (see above)
 name of the link receiving the diverted flow
 method used for computing the amount of diverted flow.
3.2.6 Storage Units Storage Units are drainage system nodes that provide storage volume. Physically they could
represent storage facilities as small as a catch basin or as large as a lake. The volumetric
properties of a storage unit are described by a function or table of surface area versus height. In
addition to receiving inflows and discharging outflows to other nodes in the drainage network,
storage nodes can also lose water from surface evaporation and from seepage into native soil. The principal input parameters for storage units include:
 invert (bottom) elevation
 maximum depth
 depth-surface area data
 evaporation potential
 seepage parameters (optional)
 external inflow data (optional).
3.2.7 Conduits Conduits are pipes or channels that move water from one node to another in the conveyance
system. Their cross-sectional shapes can be selected from a variety of standard open and closed
geometries as listed in Table 3-1. Most open channels can be represented with a rectangular, trapezoidal, or user-defined irregular
cross-section shape. For the latter, a Transect object is used to define how depth varies with
distance across the cross-section (see Section 3.3.5 below). Most new drainage and sewer pipes
are circular while culverts typically have elliptical or arch shapes. Elliptical and Arch pipes come in
standard sizes that are listed in Appendix A.12 and A.13. The Filled Circular shape allows the
bottom of a circular pipe to be filled with sediment and thus limit its flow capacity. The Custom Closed Shape allows any closed geometrical shape that is symmetrical about the center line to
be defined by supplying a Shape Curve for the cross section (see Section3.3.11 below). SWMM uses the Manning equation to express the relationship between flow rate (Q), cross-
sectional area (A), hydraulic radius (R), and slope (S) in all conduits. For standard U.S. units, (^) AR S1/22/3
n
1.49
Q=^
where n is the Manning roughness coefficient. The slope S is interpreted as either the conduit
slope or the friction slope (i.e., head loss per unit length), depending on the flow routing method
used.
For pipes with Circular Force Main cross-sections either the Hazen-Williams or Darcy-Weisbach
formula is used in place of the Manning equation for fully pressurized flow. For U.S. units the
Hazen-Williams formula i s:
= SRAC1.318Q ..^540630
where C is the Hazen-Williams C-factor which varies inversely with surface roughness and is
supplied as one of the cross-section’s parameters. The Darcy-Weisbach formula is:
(^) AR S1/21/2
f
8g
Q=^
where g is the acceleration of gravity and f is the Darcy-Weisbach friction factor. For turbulent
flow, the latter is determined from the height of the roughness elements on the walls of the pipe
(supplied as an input parameter) and the flow’s Reynolds Number using the Colebrook-White
equation. The choice of which equation to use is a user-supplied option.
A conduit does not have to be assigned a Force Main shape for it to pressurize. Any of
the closed cross-section shapes can potentially pressurize and thus function as force
mains that use the Manning equation to compute friction losses.
A constant rate of exfiltration of water along the length of the conduit can be modeled by
supplying a Seepage Rate value (in/hr or mm/hr). This only accounts for seepage losses, not
infiltration of rainfall dependent groundwater. The latter can be modeled using SWMM’s RDII
feature (see Section 3.3.6).
Table 3-1 Available cross section shapes for conduits
Name Parameters Shape Name Parameters Shape Circular Full Height
Circular Force
Main
Full Height,
Roughness
Filled Circular
Full Height,
Filled Depth
Rectangular -
Closed
Full Height,
Width (^)
Rectangular
  • Open
Full Height,
Width
Trapezoidal
Full Height,
Base Width,
Side Slopes
Triangular Full Height,
Top Width
Horizontal
Ellipse
Full Height,
Max. Width
Vertical
Ellipse
Full Height,
Max. Width
Arch
Full Height,
Max. Width
Parabolic Full Height,
Top Width
Power
Full Height,
Top Width,
Exponent (^)
Rectangular-
Triangular
Full Height,
Top Width,
Triangle
Height
Rectangular-
Round
Full Height,
Top Width,
Bottom
Radius
Modified
Baskethandle
Full Height,
Bottom
Width,
Top Radius
Egg Full Height
Horseshoe Full Height
Gothic Full Height
Catenary Full Height
Semi-Elliptical Full Height
Baskethandle Full Height
Semi-Circular Full Height
Irregular
Natural
Channel
Transect
Coordinates
Custom
Closed Shape
Full Height,
Shape
Curve
Coordinates A conduit can also be designated to act as a culvert (see Figure 3-2) if a Culvert Inlet Geometry
code number is assigned to it. These code numbers are listed in Appendix A.10. Culvert conduits
are checked continuously during dynamic wave flow routing to see if they operate under Inlet
Control as defined in the Federal Highway Administration’s publication Hydraulic Design of
Highway Culverts Third Edition (Publication No. FHWA-HIF-12-026, April 2012). Under inlet
control a culvert obeys a particular flow versus inlet depth rating curve whose shape depends on
the culvert’s shape, size, slope, and inlet geometry.

FIGURE 3-2 CONCRETE BOX CULVERT

The principal input parameters for conduits are:
 names of the inlet and outlet nodes
 offset height or elevation above the inlet and outlet node inverts
 conduit length
 Manning's roughness
 cross-sectional geometry
 entrance/exit losses (optional)
 seepage rate (optional)
 presence of a flap gate to prevent reverse flow (optional)
 inlet geometry code number if the conduit acts as a culvert (optional).
3.2.8 Pumps Pumps are links used to lift water to higher elevations. A pump curve describes the relation
between a pump’s flow rate and conditions at its inlet and outlet nodes. Five different types of
pump curves are supported: Type1
An off-line pump with a wet well
where flow increases incrementally
with available wet well volume Type2
An in-line pump where flow
increases incrementally with inlet
node depth. Type3
An in-line pump where flow varies
continuously with head difference
between the inlet and outlet nodes. Type4
A variable speed in-line pump
where flow varies continuously with
inlet node depth. Ideal
An “ideal” transfer pump whose flow rate equals the inflow rate at its inlet node. No curve is
required. The pump must be the only outflow link from its inlet node. Used mainly for preliminary
design. The on/off status of pumps can be controlled dynamically by specifying startup and shutoff water
depths at the inlet node or through user-defined Control Rules. Rules can also be used to
simulate variable speed drives that modulate pump flow. The principal input parameters for a pump include:
 names of its inlet and outlet nodes
 name of its pump curve (or * for an Ideal pump)
 initial on/off status
 startup and shutoff depths.
3.2.9 Flow Regulators Flow Regulators are structures or devices used to control and divert flows within a conveyance
system. They are typically used to:
 control releases from storage facilities
 prevent unacceptable surcharging
 divert flow to treatment facilities and interceptors
SWMM can model the following types of flow regulators: Orifices, Weirs, and Outlets. Orifices Orifices are used to model outlet and diversion structures in drainage systems, which are typically
openings in the wall of a manhole, storage facility, or control gate. They are internally represented
in SWMM as a link connecting two nodes. An orifice can have either a circular or rectangular
shape, be located either at the bottom or along the side of the upstream node, and have a flap
gate to prevent backflow. Orifices can be used as storage unit outlets under all types of flow routing. If not attached to a
storage unit node, they can only be used in drainage networks that are analyzed with Dynamic
Wave flow routing. The flow through a fully submerged orifice is computed as = 2 ghCAQ where Q = flow rate, C = discharge coefficient, A = area of orifice opening, g = acceleration of
gravity, and h = head difference across the orifice. The height of an orifice’s opening can be
controlled dynamically through user-defined Control Rules. This feature can be used to model
gate openings and closings. Flow through a partially full orifice i s computed using an equivalent
weir equation. The principal input parameters for an orifice include:
 names of its inlet and outlet nodes
 configuration (bottom or side)
 shape (circular or rectangular)
 height or elevation above the inlet node invert
 discharge coefficient
 time to open or close.
Weirs Weirs, like orifices, are used to model outlet and diversion structures in a drainage system. Weirs
are typically located in a manhole, along the side of a channel, or within a storage unit. They are
internally represented in SWMM as a link connecting two nodes, where the weir itself is placed at
the upstream node. A flap gate can be included to prevent backflow. Five varieties of weirs are available, each incorporating a different formula for computing flow
across the weir as listed in Table 3-2.

TABLE 3-2 AVAILABLE TYPES OF WEIRS

Weir Type
Cross Section
Shape
Flow Formula
Transverse Rectangular (^)
Side flow Rectangular (^)
V- notch Triangular (^)
Trapezoidal Trapezoidal (^)
Roadway Rectangular (^)
Cw = weir discharge coefficient, L = weir length, S = side slope of
V- notch or trapezoidal weir, h = head difference across the weir,
Cws = discharge coefficient through sides of trapezoidal weir.
C Lh 2/3
w
C Lh 3/5
w
ShC 2/5
w
C Lh 2/3 ShC 2/5
w + ws
C Lh 2/3
w
The Roadway weir is a broad crested rectangular weir used model roadway crossings usually in
conjunction with culvert-type conduits (see Figure 3-2). It uses curves from the Federal Highway
Administration publication Hydraulic Design of Highway Culverts Third Edition (Publication No.
FHWA-HIF-12-026, April 2012) to determine CW as a function of h and roadway width.
Weirs can be used as storage unit outlets under all types of flow routing. If not attached to a
storage unit, they can only be used in drainage networks that are analyzed with Dynamic Wave
flow routing.
The height of the weir crest above the inlet node invert can be controlled dynamically through
user-defined Control Rules. This feature can be used to model inflatable dams.
Weirs can either be allowed to surcharge or not. A surcharged weir will use an equivalent orifice
equation to compute the flow through it. Weirs placed in open channels would normally not be
allowed to surcharge while those placed in closed diversion structures or those used to represent
storm drain inlet openings would be allowed to. The principal input parameters for a weir include:
 names of its inlet and outlet nodes
 shape and geometry
 crest height or elevation above the inlet node invert
 discharge coefficient.
Outlets Outlets are flow control devices that are typically used to control outflows from storage units.
They are used to model special head-discharge relationships that cannot be characterized by
pumps, orifices, or weirs. Outlets are internally represented in SWMM as a link connecting two
nodes. An outlet can also have a flap gate that restricts flow to only one direction. Outlets attached to storage units are active under all types of flow routing. If not attached to a
storage unit, they can only be used in drainage networks analyzed with Dynamic Wave flow
routing. A user-defined rating curve determines an outlet’s discharge flow as a function of either the
freeboard depth above the outlet’s opening or the head difference across it. Control Rules can be
used to dynamically adjust this flow when certain conditions exist. The principal input parameters for an outlet include:
 names of its inlet and outlet nodes
 height or elevation above the inlet node invert
 function or table containing its head (or depth) - discharge relationship.
3.2.10 Map Labels Map Labels are optional text labels added to SWMM’s Study Area Map to help identify particular
objects or regions of the map. The labels can be drawn in any Windows font, freely edited and be
dragged to any position on the map.

3.3 Non-Visual Objects

In addition to physical objects that can be displayed visually on a map, SWMM utilizes several
classes of non-visual data objects to describe additional characteristics and processes within a
study area. 3.3.1 Climatology Temperature Air temperature data are used when simulating snowfall and snowmelt processes during runoff
calculations. They can also be used to compute daily evaporation rates. If these processes are
not being simulated then temperature data are not required. Air temperature data can be supplied
to SWMM from one of the following sources:
 a user-defined time series of point values (values at intermediate times are interpolated)
 an external climate file containing daily minimum and maximum values (SWMM fits a
sinusoidal curve through these values depending on the day of the year).
For user-defined time series, temperatures are in degrees F for US units and degrees C for
metric units. The external climate file can also be used to directly supply evaporation and wind
speed as well. Evaporation Evaporation can occur for standing water on subcatchment surfaces, for subsurface water in
groundwater aquifers, for water traveling through open channels, and for water held in storage
units. Evaporation rates can be stated as:
 a single constant value
 a set of monthly average values
 a user-defined time series of values
 values computed from the daily temperatures contained in an external climate file
 daily values read directly from an external climate file.
If rates are read directly from a climate file, then a set of monthly pan coefficients should also be
supplied to convert the pan evaporation data to free water-surface values. An option is also
available to allow evaporation only during periods with no precipitation. Note that the evaporation rates supplied to SWMM are potential rates. The actual amount of
water evaporated will depend on the amount of water available. Wind Speed Wind speed is an optional climatic variable that is only used for snowmelt calculations. SWMM
can use either a set of monthly average speeds or wind speed data contained in the same
climate file used for daily minimum/maximum temperatures. Snowmelt Snowmelt parameters are climatic variables that apply across the entire study area when
simulating snowfall and snowmelt. They include:
 the air temperature at which precipitation falls as snow
 heat exchange properties of the snow surface
 study area elevation, latitude, and longitude correction
Areal Depletion Areal depletion refers to the tendency of accumulated snow to melt non-uniformly over the
surface of a subcatchment. As the melting process proceeds, the area covered by snow gets
reduced. This behavior is described by an Areal Depletion Curve that plots the fraction of total
area that remains snow covered against the ratio of the actual snow depth to the depth at which
there is 100% snow cover. A typical ADC for a natural area is shown in Figure 3-3. Two such
curves can be supplied to SWMM, one for impervious areas and another for pervious areas.

FIGURE 3-3 AREAL DEPLETION CURVE FOR A NATURAL AREA

Climate Adjustments Climate Adjustments are optional modifications applied to the temperature, evaporation rate, and
rainfall intensity that SWMM would otherwise use at each time step of a simulation. Separate sets
of adjustments that vary periodically by month of the year can be assigned to these variables.
They provide a simple way to examine the effects of future climate change without having to
modify the original climatic time series. In a similar manner, a set of monthly adjustments can be applied to the hydraulic conductivity
used in computing rainfall infiltration on pervious land surfaces and exfiltration from storage
nodes and conduits. These can reflect the increase of hydraulic conductivity with increasing
temperature or the effect that seasonal changes in land surface conditions, such as frozen
ground, can have on infiltration capacity. 3.3.2 Snow Packs Snow Pack objects contain parameters that characterize the buildup, removal, and melting of
snow over three types of sub-areas within a subcatchment:
 The Plowable snow pack area consists of a user-defined fraction of the total impervious
area. It is meant to represent such areas as streets and parking lots where plowing and
snow removal can be done.
 The Impervious snow pack area covers the remaining impervious area of a
subcatchment.
 The Pervious snow pack area encompasses the entire pervious area of a subcatchment.
Each of these three areas is characterized by the following parameters:
 Minimum and maximum snow melt coefficients
 minimum air temperature for snow melt to occur
 snow depth above which 100% areal coverage occurs
 initial snow depth
 initial and maximum free water content in the pack.
In addition, a set of snow removal parameters can be assigned to the Plowable area. These
parameters consist of the depth at which snow removal begins and the fractions of snow moved
onto various other areas. Subcatchments are assigned a snow pack object through their Snow Pack property. A single
snow pack object can be applied to any number of subcatchments. Assigning a snow pack to a
subcatchment simply establishes the melt parameters and initial snow conditions for that
subcatchment. Internally, SWMM creates a “physical” snow pack for each subcatchment, which
tracks snow accumulation and melting for that particular subcatchment based on its snow pack
parameters, its amount of pervious and impervious area, and the precipitation history it sees. 3.3.3 Aquifers Aquifers are sub-surface groundwater zones used to model the vertical movement of water
infiltrating from the subcatchments that lie above them. They also permit the infiltration of
groundwater into the drainage system, or exfiltration of surface water from the drainage system,
depending on the hydraulic gradient that exists. Aquifers are only required in models that need to
explicitly account for the exchange of groundwater with the drainage system or to establish base
flow and recession curves in natural channels and non-urban systems. The parameters of an
aquifer object can be shared by several subcatchments but there is no exchange of groundwater
between subcatchments. A drainage system node can exchange groundwater with more than
one subcatchment. Aquifers are represented using two zones – an un-saturated zone and a saturated zone. Their
behavior is characterized using such parameters as soil porosity, hydraulic conductivity, evapotranspiration depth, bottom elevation, and loss rate to deep groundwater. In addition, the
initial water table elevation and initial moisture content of the unsaturated zone must be supplied. Aquifers are connected to subcatchments and to drainage system nodes through a
subcatchment’s Groundwater Flow property. This property also contains parameters that govern
the rate of groundwater flow between the aquifer’s saturated zone and the drainage system node. 3.3.4 Unit Hydrographs Unit Hydrographs (UHs) estimate rainfall-dependent infiltration/inflow (RDII) into a sewer system.
A UH set contains up to three such hydrographs, one for a short-term response, one for an
intermediate-term response, and one for a long-term response. A UH group can have up to 12
UH sets, one for each month of the year. Each UH group is considered as a separate object by
SWMM, and is assigned its own unique name along with the name of the rain gage that supplies
rainfall data to it. Each unit hydrograph, as shown in Figure 3-4, is defined by three parameters:
 R: the fraction of rainfall volume that enters the sewer system
 T: the time from the onset of rainfall to the peak of the UH in hours
 K: the ratio of time to recession of the UH to the time to peak

FIGURE 3-4 AN RDII UNIT HYDROGRAPH

Each unit hydrograph can also have a set of Initial Abstraction (IA) parameters associated with it.
These determine how much rainfall is lost to interception and depression storage before any
excess rainfall is generated and transformed into RDII flow by the hydrograph. The IA parameters
consist of:
 a maximum possible depth of IA (inches or mm),
 a recovery rate (inches/day or mm/day) at which stored IA is depleted during dry periods,
 an initial depth of stored IA (inches or mm).
To generate RDII into a drainage system node, the node must identify (through its Inflows
property) the UH group and the area of the surrounding sewershed that contributes RDII flow.
Unit hydrographs could also be used to replace SWMM's main rainfall-runoff process that
uses Subcatchment objects, provided that properly calibrated UHs are utilized. In this
case what SWMM calls RDII inflow to a node would actually represent overland runoff.
An alternative to using unit hydrographs to define RDII flow is to create an external RDII
interface file, which contains RDII time series data. See Section 11.7 Interface Files.
3.3.5 Transects Transects refer to the geometric data that describe how bottom elevation varies with horizontal
distance over the cross section of a natural channel or irregular-shaped conduit. Figure 3-5
displays an example transect for a natural channel.

FIGURE 3-5 EXAMPLE OF A NATURAL CHANNEL TRANSECT

Each transect must be given a unique name. Conduits refer to that name to represent their
shape. A special Transect Editor is available for editing the station-elevation data of a transect.
SWMM internally converts these data into tables of area, top width, and hydraulic radius versus
channel depth. In addition, as shown in Figure 3-5, each transect can have a left and right
overbank section whose Manning’s roughness can be different from that of the main channel.
This feature can provide more realistic estimates of channel conveyance under high flow
conditions. 3.3.6 External Inflows In addition to inflows originating from subcatchment runoff and groundwater, drainage system
nodes can receive three other types of external inflows:
 Direct Inflows - These are user-defined time series of inflows added directly into a node.
They can be used to perform flow and water quality routing in the absence of any runoff
computations (as in a study area where no subcatchments are defined).
 Dry Weather Inflows - These are continuous inflows that typically reflect the contribution
from sanitary sewage in sewer systems or base flows in pipes and stream channels.
They are represented by an average inflow rate that can be periodically adjusted on a
monthly, daily, and hourly basis by applying Time Pattern multipliers to this average
value.
 Rainfall-Dependent Infiltration/Inflow (RDII) - These are stormwater flows that enter
sanitary or combined sewers due to "inflow" from direct connections of downspouts,
sump pumps, foundation drains, etc. as well as "infiltration" of subsurface water through
cracked pipes, leaky joints, poor manhole connections, etc. RDII can be computed for a
given rainfall record based on set of triangular unit hydrographs (UH) that determine a
short-term, intermediate-term, and long-term inflow response for each time period of
rainfall. Any number of UH sets can be supplied for different sewershed areas and
different months of the year. RDII flows can also be specified in an external RDII interface
file.
Direct, Dry Weather, and RDII inflows are properties associated with each type of drainage
system node (junctions, outfalls, flow dividers, and storage units) and can be specified when
nodes are edited. They can be used to perform flow and water quality routing in the absence of
any runoff computations (as in a study area where no subcatchments are defined). It is also
possible to make the outflows generated from an upstream drainage system be the inflows to a
downstream system by using interface files. See Section 11.7 for further details. 3.3.7 Control Rules Control Rules determine how pumps and regulators in the drainage system will be adjusted over
the course of a simulation. Some examples of these rules are: Simple time-based pump control:
RULE R1
IF SIMULATION TIME > 8
THEN PUMP 12 STATUS = ON
ELSE PUMP 12 STATUS = OFF Multiple-condition orifice gate control:
RULE R2A
IF NODE 23 DEPTH > 12
AND LINK 165 FLOW > 100
THEN ORIFICE R55 SETTING = 0.5

RULE R2B

IF NODE 23 DEPTH > 12

AND LINK 165 FLOW > 200

THEN ORIFICE R55 SETTING = 1.0

RULE R2C

IF NODE 23 DEPTH <= 12

OR LINK 165 FLOW <= 100

THEN ORIFICE R55 SETTING = 0

Pump station operation:
RULE R3A
IF NODE N1 DEPTH > 5
THEN PUMP N1A STATUS = ON RULE R3B
IF NODE N1 DEPTH > 7
THEN PUMP N1B STATUS = ON RULE R3C
IF NODE N1 DEPTH <= 3
THEN PUMP N1A STATUS = OFF
AND PUMP N1B STATUS = OFF Modulated weir height control:
RULE R4
IF NODE N2 DEPTH >= 0
THEN WEIR W25 SETTING = CURVE C25 Appendix C.3 describes the control rule format in more detail and the special Editor used to edit
them. 3.3.8 Pollutants SWMM can simulate the generation, inflow and transport of any number of user-defined
pollutants. Required information for each pollutant includes:
 pollutant name
 concentration units (i.e., milligrams/liter, micrograms/liter, or counts/liter)
 concentration in rainfall
 concentration in groundwater
 concentration in inflow/infiltration
 concentration in dry weather flow
 initial concentration throughout the conveyance system
 first-order decay coefficient.
Co-pollutants can also be defined in SWMM. For example, pollutant X can have a co-pollutant Y,
meaning that the runoff concentration of X will have some fixed fraction of the runoff
concentration of Y added to it. Pollutant buildup and washoff from subcatchment areas are determined by the land uses
assigned to those areas. Input loadings of pollutants to the drainage system can also originate
from external time series inflows as well as from dry weather inflows. 3.3.9 Land Uses Land Uses are categories of development activities or land surface characteristics assigned to
subcatchments. Examples of land use activities are residential, commercial, industrial, and
undeveloped. Land surface characteristics might include rooftops, lawns, paved roads,
undisturbed soils, etc. Land uses are used solely to account for spatial variation in pollutant
buildup and washoff rates within subcatchments. The SWMM user has many options for defining land uses and assigning them to subcatchment
areas. One approach is to assign a mix of land uses for each subcatchment, which results in all
land uses within the subcatchment having the same pervious and impervious characteristics.
Another approach is to create subcatchments that have a single land use classification along with
a distinct set of pervious and impervious characteristics that reflects the classification. The following processes can be defined for each land use category:
 pollutant buildup
 pollutant washoff
 street cleaning.
Pollutant Buildup Pollutant buildup that accumulates within a land use category is described (or “normalized”) by
either a mass per unit of subcatchment area or per unit of curb length. Mass is expressed in
pounds for US units and kilograms for metric units. The amount of buildup is a function of the
number of preceding dry weather days and can be computed using one of the following functions: Power Function: Pollutant buildup (B) accumulates proportionally to time (t) raised to some
power, until a maximum limit is achieved, = ( 21 tC,CMinB C^3 )^ where C 1 = maximum buildup possible (mass per unit of area or curb length), C 2 = buildup rate
constant, and C 3 = time exponent. Exponential Function: Buildup follows an exponential growth curve that approaches a maximum
limit asymptotically,
)1(
2
1
−= eCB − tC
where C 1 = maximum buildup possible (mass per unit of area or curb length) and C 2 = buildup
rate constant (1/days). Saturation Function: Buildup begins at a linear rate that continuously declines with time until a
saturation value is reached, tC
tC
B
+
=
2
1
where C 1 = maximum buildup possible (mass per unit area or curb length) and C 2 = half-
saturation constant (days to reach half of the maximum buildup). External Time Series: This option allows one to use a Time Series to describe the rate of
buildup per day as a function of time. The values placed in the time series would have units of
mass per unit area (or curb length) per day. One can also provide a maximum possible buildup
(mass per unit area or curb length) with this option and a scaling factor that multiplies the time
series values. Pollutant Washoff Pollutant washoff from a given land use category occurs during wet weather periods and can be
described in one of the following ways: Exponential Washoff: The washoff load (W) in units of mass per hour is proportional to the
product of runoff raised to some power and to the amount of buildup remaining,
BqCW
C 2
= 1
where C 1 = washoff coefficient, C 2 = washoff exponent, q = runoff rate per unit area (inches/hour
or mm/hour), and B = pollutant buildup in mass units. The buildup here is the total mass (not per
area or curb length) and both buildup and washoff mass units are the same as used to express
the pollutant’s concentration (milligrams, micrograms, or counts). Rating Curve Washoff: The rate of washoff W in mass per second is proportional to the runoff
rate raised to some power, = 1 QCW C^2 where C 1 = washoff coefficient, C 2 = washoff exponent, and Q = runoff rate in user-defined flow
units. Event Mean Concentration: This is a special case of Rating Curve Washoff where the exponent
is 1.0 and the coefficient C 1 represents the washoff pollutant concentration in mass per liter
(Note: the conversion between user-defined flow units used for runoff and liters is handled
internally by SWMM). Note that in each case buildup is continuously depleted as washoff proceeds, and washoff
ceases when there is no more buildup available. Washoff loads for a given pollutant and land use category can be reduced by a fixed percentage
by specifying a BMP Removal Efficiency that reflects the effectiveness of any BMP controls
associated with the land use. It is also possible to use the Event Mean Concentration option by
itself, without having to model any pollutant buildup at all. Street Sweeping Street sweeping can be used on each land use category to periodically reduce the accumulated
buildup of specific pollutants. The parameters that describe street sweeping include:
 days between sweeping
 days since the last sweeping at the start of the simulation
 the fraction of buildup of all pollutants that is available for removal by sweeping
 the fraction of available buildup for each pollutant removed by sweeping
Note that these parameters can be different for each land use, and the last parameter can vary
also with pollutant. 3.3.10 Treatment Removal of pollutants from the flow streams entering any drainage system node is modeled by
assigning a set of treatment functions to the node. A treatment function can be any well-formed
mathematical expression involving:
 the pollutant concentration
 the removals of other pollutants
 any of several process variables, such as flow rate, depth, hydraulic residence time, etc.
The result of the treatment function can be either a concentration (denoted by the letter C) or a
fractional removal (denoted by R). For example, a first- order decay expression for BOD exiting
from a storage node might be expressed as:
C = BOD * exp(-0.05 * HRT)
where HRT is the reserved variable name for hydraulic residence time. The removal of some
trace pollutant that is proportional to the removal of total suspended solids (TSS) could be
expressed as:
R = 0.75 * R_TSS
Section C.22 provides more details on how user-defined treatment equations are supplied to the
program. 3.3.11 Curves Curve objects are used to describe a functional relationship between two quantities. The following
types of curves are used in SWMM:
 Storage - describes how the surface area of a Storage Unit node varies with water depth.
 Shape - describes how the width of a customized cross-sectional shape varies with
height for a Conduit link.
 Diversion - relates diverted outflow to total inflow for a Flow Divider node.
 Tidal - describes how the stage at an Outfall node changes by hour of the day.
 Pump - relates flow through a Pump link to the depth or volume at the upstream node or
to the head delivered by the pump.
 Rating - relates flow through an Outlet link to the freeboard depth or head difference
across the outlet.
 Control - determines how the control setting of a pump or flow regulator varies as a
function of some control variable (such as water level at a particular node) as specified in
a Modulated Control rule.
Each curve must be given a unique name and can be assigned any number of data pairs. 3.3.12 Time Series Time Series objects are used to describe how certain object properties vary with time. Time
series can be used to describe:
 temperature data
 evaporation data
 rainfall data
 water stage at outfall nodes
 external inflow hydrographs at drainage system nodes
 external inflow pollutographs at drainage system nodes
 control settings for pumps and flow regulators..
Each time series must be given a unique name and can be assigned any number of time-value
data pairs. Time can be specified either as hours from the start of a simulation or as an absolute
date and time-of-day. Time series data can either be entered directly into the program or be
accessed from a user-supplied Time Series file.
For rainfall time series, it is only necessary to enter periods with non-zero rainfall
amounts. SWMM interprets the rainfall value as a constant value lasting over the
recording interval specified for the rain gage that utilizes the time series. For all other
types of time series, SWMM uses interpolation to estimate values at times that fall in
between the recorded values.
For times that fall outside the range of the time series, SWMM will use a value of 0 for
rainfall and external inflow time series, and either the first or last series value for
temperature, evaporation, and water stage time series.
3.3.13 Time Patterns Time Patterns allow external Dry Weather Flow (DWF) to vary in a periodic fashion. They consist
of a set of adjustment factors applied as multipliers to a baseline DWF flow rate or pollutant
concentration. The different types of time patterns include:
Monthly - one multiplier for each month of the year
Daily - one multiplier for each day of the week
Hourly - one multiplier for each hour from 12 AM to 11 PM
Weekend - hourly multipliers for weekend days
Each Time Pattern must have a unique name and there is no limit on the number of patterns that
can be created. Each dry weather inflow (either flow or quality) can have up to four patterns
associated with it, one for each type listed above. 3.3.14 LID Controls LID Controls are low impact development practices designed to capture surface runoff and
provide some combination of detention, infiltration, and evapotranspiration to it. They are
considered as properties of a given subcatchment, similar to how Aquifers and Snow Packs are
treated. SWMM can explicitly model eight different generic types of LID controls:
Bio-retention Cells are depressions that contain vegetation grown in an
engineered soil mixture placed above a gravel drainage bed. They
provide storage, infiltration and evaporation of both direct rainfall and
runoff captured from surrounding areas.
Rain Gardens are a type of bio-retention cell consisting of just the
engineered soil layer with no gravel bed below it.
Green Roofs are another variation of a bio-retention cell that have a soil
layer laying atop a special drainage mat material that conveys excess
percolated rainfall off of the roof.
Infiltration Trenches are narrow ditches filled with gravel that intercept
runoff from upslope impervious areas. They provide storage volume and
additional time for captured runoff to infiltrate the native soil below.
Continuous Permeable Pavement systems are excavated areas filled
with gravel and paved over with a porous concrete or asphalt mix.
Normally all rainfall will immediately pass through the pavement into the
gravel storage layer below it where it can infiltrate at natural rates into
the site's native soil. Block Paver systems consist of impervious paver
blocks placed on a sand or pea gravel bed with a gravel storage layer
below. Rainfall is captured in the open spaces between the blocks and
conveyed to the storage zone and native soil below.
Rain Barrels (or Cisterns) are containers that collect roof runoff during
storm events and can either release or re-use the rainwater during dry
periods.
Rooftop Disconnection has downspouts discharge to pervious
landscaped areas and lawns instead of directly into storm drains. It can
also model roofs with directly connected drains that overflow onto
pervious areas.
Vegetative Swales are channels or depressed areas with sloping sides
covered with grass and other vegetation. They slow down the
conveyance of collected runoff and allow it more time to infiltrate the
native soil beneath it.
Bio-retention cells, infiltration trenches, and permeable pavement systems can contain optional
drain systems in their gravel storage beds to convey excess captured runoff off of the site and
prevent the unit from flooding. They can also have an impermeable floor or liner that prevents any
infiltration into the native soil from occurring. Infiltration trenches and permeable pavement
systems can also be subjected to a decrease in hydraulic conductivity over time due to clogging. Although some LID practices can also provide significant pollutant reduction benefits, at this time
SWMM only models the reduction in runoff mass load resulting from the reduction in runoff flow
volume. There are two different approaches for placing LID controls within a subcatchment:  place one or more controls in an existing subcatchment that will displace an equal amount of
non-LID area from the subcatchment  create a new subcatchment devoted entirely to just a single LID practice. The first approach allows a mix of LIDs to be placed into a subcatchment, each treating a
different portion of the runoff generated from the non-LID fraction of the subcatchment. Note that
under this option the subcatchment’s LIDs act in parallel — it is not possible to make them act in
series (i.e., have the outflow from one LID control become the inflow to another LID). Also, after
LID placement the subcatchment’s Percent Impervious and Width properties may require
adjustment to compensate for the amount of original subcatchment area that has now been
replaced by LIDs (see Figure 3-6 below). For example, suppose that a subcatchment which is
40% impervious has 75% of that area converted to a permeable pavement LID. After the LID is
added the subcatchment’s percent imperviousness should be changed to the percent of
impervious area remaining divided by the percent of non-LID area remaining. This works out to ( 1
  • 0.75)40 / (100 – 0.7540) or 14.3 %.

FIGURE 3-6 ADJUSTMENT OF SUBCATCHMENT PARAMETERS AFTER LID PLACEMENT

Under this first approach the runoff available for capture by the subcatchment’s LIDs is the runoff
generated from its impervious area. If the option to re-route some fraction of this runoff to the
pervious area is exercised, then only the remaining impervious runoff (if any) will be available for
LID treatment. Also note that green roofs and roof disconnection only treat the precipitation that falls directly on them and do not capture runoff from other impervious areas in their
subcatchment. The second approach allows LID controls to be strung along in series and also allows runoff from
several different upstream subcatchments to be routed onto the LID subcatchment. If these
single-LID subcatchments are carved out of existing subcatchments, then once again some
adjustment of the Percent Impervious, Width and also the Area properties of the latter may be
necessary. In addition, whenever an LID occupies the entire subcatchment the values assigned
to the subcatchment’s standard surface properties (such as imperviousness, slope, roughness,
etc.) are overridden by those that pertain to the LID unit. Normally both surface and drain outflows from LID units are routed to the same outlet location
assigned to the parent subcatchment. However one can choose to return all LID outflow to the
pervious area of the parent subcatchment and/or route the drain outflow to a separate designated
outlet. (When both of these options are chosen, only the surface outflow is returned to the
pervious sub-area.)

3.4 Computational Methods

SWMM is a physically based, discrete-time simulation model. It employs principles of
conservation of mass, energy, and momentum wherever appropriate. This section briefly
describes the methods SWMM uses to model stormwater runoff quantity and quality through the
following physical processes:




Surface Runoff
Groundwater
Flow Routing
Water Quality Routing

Infiltration
Snowmelt
Surface Ponding
3.4.1 Surface Runoff The conceptual view of surface runoff used by SWMM is illustrated in Figure 3-7 below. Each
subcatchment surface is treated as a nonlinear reservoir. Inflow comes from precipitation and any
designated upstream subcatchments. There are several outflows, including infiltration,
evaporation, and surface runoff. The capacity of this “reservoir” is the maximum depression
storage, which is the maximum surface storage provided by ponding, surface wetting, and
interception. Surface runoff per unit area, Q, occurs only when the depth of water in the
“reservoir” exceeds the maximum depression storage, ds, in which case the outflow is given by
Manning’s equation. Depth of water over the subcatchment (d) is continuously updated with time
by solving numerically a water balance equation over the subcatchment.

FIGURE 3-7 CONCEPTUAL VIEW OF SURFACE RUNOFF xi

3.4.2 Infiltration Infiltration is the process of rainfall penetrating the ground surface into the unsaturated soil zone
of pervious subcatchments areas. SWMM offers four choices for modeling infiltration: Horton’s Method
This method is based on empirical observations showing that infiltration decreases exponentially
from an initial maximum rate to some minimum rate over the course of a long rainfall event. Input
parameters required by this method include the maximum and minimum infiltration rates, a decay
coefficient that describes how fast the rate decreases over time, and a time it takes a fully
saturated soil to completely dry. Modified Horton Method
This is a modified version of the classical Horton Method that uses the cumulative infiltration in
excess of the minimum rate as its state variable (instead of time along the Horton curve),
providing a more accurate infiltration estimate when low rainfall intensities occur. It uses the same
input parameters as does the traditional Horton Method. Green-Ampt Method
This method for modeling infiltration assumes that a sharp wetting front exists in the soil column,
separating soil with some initial moisture content below from saturated soil above. The input
parameters required are the initial moisture deficit of the soil, the soil’s hydraulic conductivity, and
the suction head at the wetting front. The recovery rate of moisture deficit during dry periods is
empirically related to the hydraulic conductivity. Modified Green-Ampt Method
This method modifies the original Green-Ampt procedure by not depleting moisture deficit in the
top surface layer of soil during initial periods of low rainfall as was done in the original method.
This change can produce more realistic infiltration behavior for storms with long initial periods
where the rainfall intensity is below the soil’s saturated hydraulic conductivity. Curve Number Method
This approach is adopted from the NRCS (SCS) Curve Number method for estimating runoff. It
assumes that the total infiltration capacity of a soil can be found from the soil’s tabulated Curve
Number. During a rain event this capacity is depleted as a function of cumulative rainfall and
remaining capacity. The input parameters for this method are the curve number and the time it
takes a fully saturated soil to completely dry. SWMM also allows the infiltration recovery rate to be adjusted by a fixed amount on a monthly
basis to account for seasonal variation in such factors as evaporation rates and groundwater
levels. This optional monthly soil recovery pattern is specified as part of a project’s Evaporation
data. 3.4. 3 Groundwater Figure 3-8 is a definitional sketch of the two-zone groundwater model that is used in SWMM. The
upper zone is unsaturated with a variable moisture content of θ. The lower zone is fully saturated
and therefore its moisture content is fixed at the soil porosity φ. The fluxes shown in the figure,
expressed as volume per unit area per unit time, consist of the following:

FIGURE 3-8 TWO-ZONE GROUNDWATER MODEL

fI infiltration from the surface fEU evapotranspiration from the upper zone which is a fixed fraction of the un-used surface
evaporation fU percolation from the upper to lower zone which depends on the upper zone moisture content
θ and depth dU fEL evapotranspiration from the lower zone, which is a function of the depth of the upper zone dU fL seepage from the lower zone to deep groundwater which depends on the lower zone depth
dL fG lateral groundwater interflow to the drainage system, which depends on the lower zone depth
dL as well as the depth in the receiving channel or node. After computing the water fluxes that exist during a given time step, a mass balance is written for
the change in water volume stored in each zone so that a new water table depth and unsaturated
zone moisture content can be computed for the next time step. 3.4. 4 Snowmelt The snowmelt routine in SWMM is a part of the runoff modeling process. It updates the state of
the snow packs associated with each subcatchment by accounting for snow accumulation, snow
redistribution by areal depletion and removal operations, and snow melt via heat budget
accounting. Any snowmelt coming off the pack is treated as an additional rainfall input onto the
subcatchment. At each runoff time step the following computations are made:
  1. Air temperature and melt coefficients are updated according to the calendar date.
  2. Any precipitation that falls as snow is added to the snow pack.
  3. Any excess snow depth on the plowable area of the pack is redistributed according to the
    removal parameters established for the pack.
  4. Areal coverage of snow on the impervious and pervious areas of the pack is reduced
    according to the Areal Depletion Curves defined for the study area.
  5. The amount of snow in the pack that melts to liquid water is found using:
    a. a heat budget equation for periods with rainfall, where melt rate increases with
    increasing air temperature, wind speed, and rainfall intensity
    b. a degree-day equation for periods with no rainfall, where melt rate equals the
    product of a melt coefficient and the difference between the air temperature and
    the pack’s base melt temperature.
  6. If no melting occurs, the pack temperature is adjusted up or down based on the product
    of the difference between current and past air temperatures and an adjusted melt
    coefficient. If melting occurs, the temperature of the pack is increased by the equivalent
    heat content of the melted snow, up to the base melt temperature. Any remaining melt
    liquid beyond this is available to runoff from the pack.
  7. The available snowmelt is then reduced by the amount of free water holding capacity
    remaining in the pack. The remaining melt is treated the same as an additional rainfall
    input onto the subcatchment.
3.4. 5 Flow Routing Flow routing within a conduit link in SWMM is governed by the conservation of mass and
momentum equations for gradually varied, unsteady flow (i.e., the Saint Venant flow equations).
The SWMM user has a choice on the level of sophistication used to solve these equations:
 Steady Flow Routing
 Kinematic Wave Routing
 Dynamic Wave Routing
Each of these routing methods employs the Manning equation to relate flow rate to flow depth
and bed (or friction) slope. For user-designated Force Main conduits, either the Hazen-Williams
or Darcy-Weisbach equation can be used when pressurized flow occurs. Steady Flow Routing Steady Flow routing represents the simplest type of routing possible (actually no routing) by
assuming that within each computational time step flow is uniform and steady. Thus it simply
translates inflow hydrographs at the upstream end of the conduit to the downstream end, with no
delay or change in shape. The normal flow equation is used to relate flow rate to flow area (or
depth). This type of routing cannot account for channel storage, backwater effects, entrance/exit losses,
flow reversal or pressurized flow. It can only be used with dendritic conveyance networks, where
each node has only a single outflow link (unless the node is a divider in which case two outflow
links are required). This form of routing is insensitive to the time step employed and is really only
appropriate for preliminary analysis using long-term continuous simulations. Kinematic Wave Routing This routing method solves the continuity equation along with a simplified form of the momentum
equation in each conduit. The latter assumes that the slope of the water surface equal the slope
of the conduit. The maximum flow that can be conveyed through a conduit is the full normal flow value. Any flow
in excess of this entering the inlet node is either lost from the system or can pond atop the inlet
node and be re-introduced into the conduit as capacity becomes available. Kinematic wave routing allows flow and area to vary both spatially and temporally within a
conduit. This can result in attenuated and delayed outflow hydrographs as inflow is routed
through the channel. However this form of routing cannot account for backwater effects,
entrance/exit losses, flow reversal, or pressurized flow, and is also restricted to dendritic network
layouts. It can usually maintain numerical stability with moderately large time steps, on the order
of 1 to 5 minutes. If the aforementioned effects are not expected to be significant then this
alternative can be an accurate and efficient routing method, especially for long-term simulations. Dynamic Wave Routing Dynamic Wave routing solves the complete one-dimensional Saint Venant flow equations and
therefore produces the most theoretically accurate results. These equations consist of the
continuity and momentum equations for conduits and a volume continuity equation at nodes. With this form of routing it is possible to represent pressurized flow when a closed conduit
becomes full, such that flows can exceed the full normal flow value. Flooding occurs when the water depth at a node exceeds the maximum available depth, and the excess flow is either lost
from the system or can pond atop the node and re-enter the drainage system. Dynamic wave routing can account for channel storage, backwater, entrance/exit losses, flow
reversal, and pressurized flow. Because it couples together the solution for both water levels at
nodes and flow in conduits it can be applied to any general network layout, even those containing
multiple downstream diversions and loops. It is the method of choice for systems subjected to
significant backwater effects due to downstream flow restrictions and with flow regulation via
weirs and orifices. This generality comes at a price of having to use much smaller time steps, on
the order of a thirty seconds or less (SWMM can automatically reduce the user-defined maximum
time step as needed to maintain numerical stability). 3.4. 6 Ponding and Pressurization Normally in flow routing, when the flow into a junction exceeds the capacity of the system to
transport it further downstream, the excess volume overflows the system and is lost. An option
exists to have instead the excess volume be stored atop the junction, in a ponded fashion, and be
reintroduced into the system as capacity permits. Under Steady and Kinematic Wave flow routing,
the ponded water is stored simply as an excess volume. For Dynamic Wave routing, which is
influenced by the water depths maintained at nodes, the excess volume is assumed to pond over
the node with a constant surface area. This amount of surface area is an input parameter
supplied for the junction. Alternatively, the user may wish to represent the surface overflow system explicitly. In open
channel systems this can include road overflows at bridges or culvert crossings as well as
additional floodplain storage areas. In closed conduit systems, surface overflows may be
conveyed down streets, alleys, or other surface routes to the next available stormwater inlet or
open channel. Overflows may also be impounded in surface depressions such as parking lots,
back yards or other areas. In sewer systems with pressurized pipes and force mains the hydraulic head at junction nodes
can at times exceed the ground elevation under Dynamic Wave routing. This would normally
result in an overflow which, as described above, can either be lost or ponded. SWMM allows the
user to specify an additional “surcharge” depth for junction nodes that lets them pressurize and
prevents any outflow until this additional depth is exceeded. If both ponding and pressurization
are specified for a node ponding takes precedence and the surcharge depth is ignored. Neither
ponding nor pressurization applies to storage nodes. 3.4. 7 Water Quality Routing Water quality routing within conduit links assumes that the conduit behaves as a continuously
stirred tank reactor (CSTR). Although a plug flow reactor assumption might be more realistic, the
differences will be small if the travel time through the conduit is on the same order as the routing
time step. The concentration of a constituent exiting the conduit at the end of a time step is found
by integrating the conservation of mass equation, using average values for quantities that might
change over the time step such as flow rate and conduit volume. Water quality modeling within storage unit nodes follows the same approach used for conduits.
For other types of nodes that have no volume, the quality of water exiting the node is simply the
mixture concentration of all water entering the node. The pollutant concentration in both a conduit and a storage node will be reduced by a first-order
decay reaction if the pollutant’s first-order decay coefficient is not zero. 3.4.8 LID Representation LID controls are represented by a combination of vertical layers whose properties are defined on
a per-unit-area basis. This allows LIDs of the same design but differing area coverage to easily
be placed within different subcatchments of a study area. During a simulation SWMM performs a
moisture balance that keeps track of how much water moves between and is stored within each
LID layer. As an example, the layers used to model a bio-retention cell and the flow pathways
between them are shown in Figure 3-9. The various possible layers consist of the following:

FIGURE 3-9 CONCEPTUAL DIAGRAM OF A BIO-RETENTION CELL LID

 The Surface Layer corresponds to the ground (or pavement) surface that receives direct
rainfall and runon from upstream land areas, stores excess inflow in depression storage, and
generates surface outflow that either enters the drainage system or flows onto downstream
land areas.  The Pavement Layer is the layer of porous concrete or asphalt used in continuous permeable
pavement systems, or is the paver blocks and filler material used in modular systems.  The Soil Layer is the engineered soil mixture used in bio-retention cells to support vegetative
growth. It can also be a sand layer placed beneath a pavement layer to provide bedding and
filtration.  The Storage Layer is a bed of crushed rock or gravel that provides storage in bio-retention
cells, porous pavement, and infiltration trench systems. For a rain barrel it is simply the barrel
itself.  The Drain System conveys water out of the gravel storage layer of bio-retention cells,
permeable pavement systems, and infiltration trenches (typically with slotted pipes) into a
common outlet pipe or chamber. For rain barrels it is simply the drain valve at the bottom of
the barrel while for rooftop disconnection it is the roof gutter and downspout system.  The Drainage Mat Layer is a mat or plate placed between the soil media and the roof in a
green roof whose purpose is to convey any water that drains through the soil layer off of the
roof. Table 3-3 indicates which combination of layers applies to each type of LID (x means required, o
means optional).
Table 3-3 Layers used to model different types of LID units
LID Type Surface Pavement Soil Storage Drain Drainage Mat Bio-Retention Cell x x o o Rain Garden x x Green Roof x x x Permeable Pavement x x o x o Infiltration Trench x x o Rain Barrel x x Roof Disconnection x x Vegetative Swale x All of the LID controls provide some amount of rainfall/runoff storage and evaporation of stored
water (except for rain barrels). Infiltration into native soil occurs in vegetative swales and can also
occur in bio-retention cells, rain gardens, permeable pavement systems, and infiltration trenches
if those systems do not employ an optional impermeable bottom liner. Infiltration trenches and
permeable pavement systems can also be subjected to clogging. This reduces their hydraulic
conductivity over time proportional to the cumulative hydraulic loading they receive. The performance of the LID controls placed in a subcatchment is reflected in the overall runoff,
infiltration, and evaporation rates computed for the subcatchment as normally reported by
SW MM. SWMM’s Status Report also contains a section entitled LID Performance Summary that
provides an overall water balance for each LID control placed in each subcatchment. The
components of this water balance include total inflow, infiltration, evaporation, surface runoff,
drain flow and initial and final stored volumes, all expressed as inches (or mm) over the LID’s
area. Optionally, the entire time series of flux rates and moisture levels for a selected LID control
in a given subcatchment can be written to a tab delimited text file for easy viewing and graphing
in a spreadsheet program (such as Microsoft Excel).

CHAPTER 4 – SWMM’S MAIN WINDOW

This chapter discusses the essential features of SWMM’s workspace. It describes the main menu
bar, the tool and status bars, and the three windows used most often – the Study Area Map, the
Browser, and the Property Editor. It also shows how to set program preferences.

4.1 Overview

The EPA SWMM main window is pictured below. It consists of the following user interface
elements: a Main Menu, several Toolbars, a Status Bar, the Study Area Map window, a Browser
panel, and a Property Editor window. A description of each of these elements is provided in the
sections that follow.

4.2 Main Menu

The Main Menu located across the top of the EPA SWMM main window contains a collection of
menus used to control the program. These include:
 File Menu
 Edit Menu
 View Menu
 Project Menu
 Report Menu
 Tools Menu
 Window Menu
 Help Menu
File Menu The File Menu contains commands for opening and saving data files and for printing:
Command Description
New Creates a new SWMM project
Open Opens an existing project
Reopen Reopens a recently used project
Save Saves the current project
Save As Saves the current project under a different name
Export Exports study area map to a file in a variety of formats;
Exports current results to a Hot Start file;
Exports the current result’s Status/Summary reports
Combine Combines two Routing Interface files together
Page Setup Sets page margins and orientation for printing
Print Preview Previews a printout of the currently active view (map, report,
graph, or table)
Print Prints the current view
Exit Exits EPA SWMM
Edit Menu The Edit Menu contains commands for editing and copying:
Command Description
Copy To Copies the currently active view (map, report, graph or table)
to the clipboard or to a file
Select Object Enables the user to select an object on the map
Select Vertex Enables the user to select the vertex of a subcatchment or
link
Select Region Enables the user to delineate a region on the map for
selecting multiple objects
Select All Selects all objects when the map is the active window or all
cells of a table when a tabular report is the active window
Find Object Locates a specific object by name on the map
Edit Object Edits the properties of the currently selected object
Delete Object Deletes the currently selected object
Group Edit Edits a property for the group of objects that fall within the
outlined region of the map
Group Delete Deletes a group of objects that fall within the outlined region
of the map
View Menu The View Menu contains commands for viewing the Study Area Map:
Command Description
Dimensions Sets reference coordinates and distance units for the study
area map
Backdrop Allows a backdrop image to be added, positioned, and
viewed behind the map
Pan Pans across the map
Zoom In Zooms in on the map
Zoom Out Zooms out on the map
Full Extent Redraws the map at full extent
Query Highlights objects on the map that meet specific criteria
Overview Toggles the display of the Overview Map
Objects Toggles display of classes of objects on the map
Legends Controls display of the map legends
Toolbars Toggles display of toolbars
Project Menu The Project menu contains commands related to the current project being analyzed:
Command Description
Summary Lists the number of each type of object in the project
Details Shows a detailed listing of all project data
Defaults Edits a project’s default properties
Calibration Data Registers files containing calibration data with the project
Add a New Object Adds a new object to the project
Run Simulation Runs a simulation
Report Menu The Report menu contains commands used to report analysis results in different formats:
Command Description
Status Displays a status report for the most recent simulation run
Summary Displays summary results in tabular form
Graph Displays simulation results in graphical form
Table Displays simulation results in tabular form
Statistics Displays a statistical analysis of simulation results
Customize Customizes the display style of the currently active graph
Tools Menu The Tools menu contains commands used to configure program preferences, study area map
display options, and external add-in tools:
Command Description
Program
Preferences
Sets program preferences, such as font size, confirm
deletions, number of decimal places displayed, etc.
Map Display
Options
Sets appearance options for the Map, such as object size,
annotation, flow direction arrows, and back-ground color
Configure Tools Adds, deletes, or modifies external add-in tools
Window Menu The Window Menu contains commands for arranging and selecting windows within the SWMM
workspace:
Command Description
Cascade Arranges windows in cascaded style, with the study area
map filling the entire display area
Tile Minimizes the study area map and tiles the remaining
windows vertically in the display area
Close All Closes all open windows except for the study area map
Window List Lists all open windows; the currently selected window has
the focus and is denoted with a check mark
Help Menu The Help Menu contains commands for getting help in using EPA SWMM:
Command Description
Help Topics Displays the Help system's Table of Contents
How Do I Displays a list of topics covering the most common
operations
Measurement Units Shows measurement units for all of SWMM’s parameters
Error Messages Lists the meaning of all error messages
Tutorial Presents a short tutorial introducing the user to EPA
SW MM
About Lists information about the version of EPA SWMM being
used

4.3 Toolbars v

Toolbars provide shortcuts to commonly used operations. There are three such toolbars:
 Standard Toolbar
 Map Toolbar
 Object Toolbar
Individual toolbars can be made visible or invisible by selecting View >> Toolbars from the Main
Menu. The Standard Toolbar contains buttons for the following commonly used commands:
Creates a new project (File >> New)
Opens an existing project (File >> Open)
Saves the current project (File >> Save)
Prints the currently active window (File >> Print)
Copies selection to the clipboard or to a file (Edit >> Copy To)
Finds a specific object on the Study Area Map (Edit >> Find Object)
Makes a visual query of the study area map (View >> Query)
Toggles the display of the Overview Map (View >> Overview)
Runs a simulation (Project >> Run Simulation)
Displays a run’s Status or Summary reports (Report >> Status and Report
>> Summary appear in a dropdown menu)
Creates a profile plot of simulation results (Report >> Graph >> Profile)
Creates a time series plot of simulation results (Report >> Graph >> Time
Series)
Creates a time series table of simulation results (Report >> Table)
Creates a scatter plot of simulation results (Report >> Graph >> Scatter)
Performs a statistical analysis of simulation results (Report >> Statistics)
Modifies display options for the currently active view (Tools >> Map Display
Options or Report >> Customize)
Arranges windows in cascaded style, with the study area map filling the
entire display area (Window >> Cascade)
The Map Toolbar contains the following buttons for viewing the study area map:
Selects an object on the map (Edit >> Select Object)
Selects link or subcatchment vertex points (Edit >> Select Vertex)
Selects a region on the map (Edit >> Select Region)
Pans across the map (View >> Pan)
Zooms in on the map (View >> Zoom In)
Zooms out on the map (View >> Zoom Out)
Draws map at full extent (View >> Full Extent)
Measures a length or area on the map
The Object Toolbar contains buttons for adding visual objects to a project via the study area
map.
Adds a rain gage to the map.^
Adds a subcatchment to the map
Adds a junction node to the map^
Adds an outfall node to the map^
Adds a flow divider node to the map
Adds a storage unit node to the map
Adds a conduit link to the map^
Adds a pump link to the map
Adds an orifice link to the map^
Adds a weir link to the map^
Adds an outlet link to the map^
Adds a text label to the map

4.4 Status Bar

The Status Bar appears at the bottom of SWMM’s Main Window and is divided into six sections: Auto-Length
Indicates whether the automatic computation of conduit lengths and subcatchment areas is
turned on or off. The setting can be changed by clicking the drop down arrow. Offsets
Indicates whether the positions of links above the invert of their connecting nodes are expressed
as a Depth above the node invert or as the Elevation of the offset. Click the drop down arrow to
change this option. If changed, a dialog box will appear asking if all existing offsets in the current
project should be changed or not (i.e., convert Depth offsets to Elevation offsets or Elevation
offsets to Depth offsets, depending on the option selected) Flow Units
Displays the current flow units that are in effect. Click the drop down arrow to change the choice
of flow units. Selecting a US flow unit means that all other quantities will be expressed in US
units, while choosing a metric flow unit will force all quantities to be expressed in metric units. The
units of previously entered data are not automatically adjusted if the unit system is changed. Run Status
results are not available because no simulation has been run yet.
results are up to date.^
results are out of date because project data have changed.^
results are not available because the last simulation had errors.^
Zoom Level
Displays the current zoom level for the map (100% is full-scale). XY Location
Displays the map coordinates of the current position of the mouse pointer.

4.5 Study Area Map

The Study Area Map (shown below) provides a planar schematic diagram of the objects
comprising a drainage system. Its pertinent features are as follows:
 The location of objects and the distances between them do not necessarily have to
conform to their actual physical scale.
 Selected properties of these objects, such as water quality at nodes or flow velocity in
links, can be displayed by using different colors. The color-coding is described in a
Legend, which can be edited.
 New objects can be directly added to the map and existing objects can be selected for
editing, deleting, and repositioning.
 A backdrop drawing (such as a street or topographic map) can be placed behind the
network map for reference.
 The map can be zoomed to any scale and panned from one position to another.
 Nodes and links can be drawn at different sizes, flow direction arrows added, and object
symbols, ID labels and numerical property values displayed.
 The map can be printed, copied onto the Windows clipboard, or exported as a DXF file or
Windows metafile.

4.6 Project Browser

The Project Browser panel (shown below) appears when the Project tab on the left panel of
SW MM’s main window is selected. It provides access to all of the data objects in a project. The
vertical sizes of the list boxes in the browser can be adjusted by using the splitter bar located just
below the upper list box. The width of the Browser panel can be adjusted by using the splitter bar
located along its right edge.
The upper list box displays the various categories of data objects
available to a SWMM project. The lower list box lists the name of
each individual object of the currently selected data category.
The buttons between the two list boxes are used as follows:
adds a new object
deletes the selected object
edits the selected object
moves the selected object up one position
moves the selected object down one position
sorts the objects in ascending order
Selections made in the Project Browser are coordinated with
objects highlighted on the Study Area Map, and vice versa. For
example, selecting a conduit in the Browser will cause that
conduit to be highlighted on the map, while selecting it on the
map will cause it to become the selected object in the Browser.

4.7 Map Browser……………………………………………………………………………………………………..

The Map Browser panel (shown below) appears when the Map tab on the left panel of the
SW MM’s main window is selected. It controls the mapping themes and time periods viewed on
the Study Area Map. The width of the Map Browser panel can be adjusted by using the splitter
bar located along its right edge. The Map Browser consists of the following three panels that
control what results are displayed on the map:
The Themes panel selects a set of variables to view in color-
coded fashion on the Map.
The Time Period panel selects which time period of the
simulation results are viewed on the Map.
The Animator panel controls the animated display of the Study
Area Map and all Profile Plots over time.
The Themes panel of the Map Browser is used to select a thematic variable to view in color-
coded fashion on the Study Area Map.
Subcatchments - selects the theme to display for the subcatchment
areas shown on the Map.
Nodes - selects the theme to display for the drainage system nodes
shown on the Map.
Links - selects the theme to display for the drainage system links
shown on the Map.
The Time Period panel of the Map Browser allows is used to select a time period in which to view
computed results in thematic fashion on the Study Area Map.
Date - selects the day for which simulation results will be viewed.
Time of Day - selects the time of the current day (in
hours:minutes:seconds) for which simulation results will be viewed.
Elapsed Time - selects the elapsed time from the start of the
simulation (in days.hours:minutes:seconds) for which results will be
viewed.
The Animator panel of the Map Browser contains controls for animating the Study Area Map and
all Profile Plots through time i.e., updating map color-coding and hydraulic grade line profile
depths as the simulation time clock is automatically moved forward or back. The meaning of the
control buttons are as follows:
Returns to the starting period.
Starts animating backwards in time
Stops the animation
Starts animating forwards in time
The slider bar is used to adjust the animation speed.

4.8 Property Editor

The Property Editor (shown to the right) is used to edit
the properties of data objects that can appear on the
Study Area Map. It is invoked when one of these objects
is selected (either on the Map or in the Project Browser)
and double-cli cked or when the Project Browser’s Edit button is clicked. Key features of the Property Editor include:
 The Editor is a grid with two columns - one for
the property's name and the other for its value.
 The columns can be re-sized by re-sizing the
header at the top of the Editor with the mouse.
 A hint area is displayed at the bottom of the
Editor with an expanded description of the
property being edited. The size of this area can
be adjusted by dragging the splitter bar located
just above it. (^)
 The Editor window can be moved and re-sized via the normal Windows operations.
 Depending on the property, the value field can be one of the following:
o a text box in which you enter a value
o a dropdown combo box from which you select a value from a list of choices
o a dropdown combo box in which you can enter a value or select from a list of choices
o an ellipsis button which you click to bring up a specialized editor.
 The field in the Editor that currently has the focus will have a focus rectangle drawn
around it.
 Both the mouse and the Up and Down arrow keys on the keyboard can be used to move
between property fields.
 The Page Up key can be used to select the previous object of the same type (as listed in
the Project Browser) into the Editor, while the Page Down key will select the next object
of the same type into the Editor.
 To begin editing the property with the focus, either begin typing a value or hit the Enter
key.
 To have the program accept edits made in a property field, either press the Enter key or
move to another property. To cancel the edits, press the Esc key.
 The Property Editor can be hidden by clicking the button in the upper right corner of its
title bar.

4.9 Setting Program Preferences

Program preferences allow one to customize certain program features. To set program
preferences, select Program Preferences from the Tools menu. A Preferences dialog form will
appear containing two tabbed pages – one for General Preferences and one for Numerical
Precision. The following preferences can be set on the General Preferences page of the Preferences dialog:
Preference Description
Blinking Map Highlighter Check to make the selected object on the study area map
blink on and off
Flyover Map Labeling Check to display the ID label and current theme value in a
hint-style box whenever the mouse is placed over an object
on the study area map
Confirm Deletions Check to display a confirmation dialog box before deleting
any object
Automatic Backup File Check to save a backup copy of a newly opened project to
disk named with a .bak extension
Report Elapsed Time by
Default
Check to use elapsed time (rather than date/time) as the
default for time series graphs and tables.
Prompt to Save Results If left unchecked then simulation results are automatically
saved to disk when the current project is closed. Otherwise
the user will be asked if results should be saved.
Clear File List Check to clear the list of most recently used files that appears
when File >> Reopen is selected from the Main Menu
Style Theme Selects a color theme to use for SWMM’s user interface (see
below for some examples)
The Numerical Precision page of the Preferences dialog controls the number of decimal places
displayed when simulation results are reported. Use the dropdown list boxes to select a specific
Subcatchment, Node or Link parameter, and then use the edit boxes next to them to select the
number of decimal places to use when displaying computed results for the parameter. Note that
the number of decimal places displayed for any particular input design parameter, such as slope,
diameter, length, etc. is whatever the user enters.

CHAPTER 5 – WORKING WITH PROJECTS

Project files contain all of the information used to model a study area. They are usually named
with a .INP extension. This section describes how to create, open, and save EPA SWMM projects
as well as setting their default properties.

5.1 Creating a New Project

To create a new project:
  1. Select File >> New from the Main Menu or click on the Standard Toolbar.
  2. You will be prompted to save the existing project (if changes were made to it) before the
    new project is created.
  3. A new, unnamed project is created with all options set to their default values.
A new project is automatically created whenever EPA SWMM first begins.
If you are going to use a backdrop image with automatic area and length calculation, then
it is recommended that you set the map dimensions immediately after creating the new
project (see Section 7.2 Setting the Map's Dimensions).

5.2 Opening an Existing Project

To open an existing project stored on disk:
  1. Either select File >> Open from the Main Menu or click on the Standard Toolbar.
  2. You will be prompted to save the current project (if changes were made to it).
  3. Select the file to open from the Open File dialog form that will appear.
  4. Click Open to open the selected file.
To open a project that was worked on recently:
  1. Select File >> Reopen from the Main Menu.
  2. Select a file from the list of recently used files to open.

5.3 Saving a Project

To save a project under its current name either select File >> Save from the Main Menu or click
on the Standard Toolbar.
To save a project using a different name:
  1. Select File >> Save As from the Main Menu.
  2. A standard File Save dialog form will appear from which you can select the folder and
    name that the project should be saved under.

5.4 Setting Project Defaults

Each project has a set of default values that are used unless overridden by the SWMM user.
These values fall into three categories:
  1. Default ID labels (labels used to identify nodes and links when they are first created)
  2. Default subcatchment properties (e.g., area, width, slope, etc.)
  3. Default node/link properties (e.g., node invert, conduit length, routing method).
To set default values for a project:
  1. Select Project >> Defaults from the Main Menu.
  2. A Project Defaults dialog will appear with three pages, one for each category listed
    above.
  3. Check the box in the lower left of the dialog form if you want to save your choices for use
    in all new future projects as well.
  4. Click OK to accept your choice of defaults.
The specific items for each category of defaults will be discussed next. Default ID Labels The ID Labels page of the Project Defaults dialog form is used to determine how SWMM will
assign default ID labels for the visual project components when they are first created. For each
type of object you can enter a label prefix in the corresponding entry field or leave the field blank
if an object’s default name will simply be a number. In the last field you can enter an increment to
be used when adding a numerical suffix to the default label. As an example, if C were used as a
prefix for Conduits along with an increment of 5, then as conduits are created they receive default
names of C5, C10, C15, and so on. An object’s default name can be changed by using the
Property Editor for visual objects or the object-specific editor for non-visual objects. Default Subcatchment Properties The Subcatchment page of the Project Defaults dialog sets default property values for newly
created subcatchments. These properties include:
 Subcatchment Area
 Characteristic Width
 Slope
 % Impervious
 Impervious Area Roughness
 Pervious Area Roughness
 Impervious Area Depression Storage
 Pervious Area Depression Storage
 % of Impervious Area with No Depression Storage
 Infiltration Method
The default properties of a subcatchment can be modified later by using the Property Editor. Default Node/Link Properties The Nodes/Links page of the Project Defaults dialog sets default property values for newly
created nodes and links. These properties include:
 Node Invert Elevation
 Node Maximum Depth
 Node Ponded Area
 Conduit Length
 Conduit Shape and Size
 Conduit Roughness
 Flow Units
 Link Offsets Convention
 Routing Method
 Force Main Equation
The defaults automatically assigned to individual objects can be changed by using the object’s
Property Editor. The choice of Flow Units and Link Offsets Convention can be changed directly
on the main window’s Status Bar.

5.5 Measurement Units

SWMM can use either US units or SI metric units. The choice of flow units determines what unit
system is used for all other quantities:
 selecting CFS (cubic feet per second), GPM (gallons per minutes), or MGD (million
gallons per day) for flow units implies that US units will be used throughout
 selecting CMS (cubic meters per second), LPS (liters per second), or MLD (million liters
per day) as flow units implies that SI units will be used throughout.
Flow units can be selected directly on the main window’s Status Bar or by setting a project’s
default values. In the latter case the selection can be saved so that all new future projects will
automatically use those units.
The units of previously entered data are not automatically adjusted if the unit system is
changed.

5.6 Link Offset Conventions

Conduits and flow regulators (orifices, weirs, and outlets) can be offset some distance above the
invert of their connecting end nodes as depicted below:

5.7 Calibration Data

There are two different conventions available for specifying the location of these offsets. The Depth convention uses the offset distance from the node’s invert (distance between  and ‚ in
the figure above). The Elevation convention uses the absolute elevation of the offset location (the elevation of point  in the figure). The choice of convention can be made on the Status Bar of
SWMM’s main window or on the Node/Link Properties page of the Project Defaults dialog. When
thi s convention is changed, a dialog will appear giving one the option to automatically re-calculate
all existing link offsets in the current project using the newly selected convention SWMM can compare the results of a simulation with measured field data in its Time Series Plots,
which are discussed in section 9.4. Before SWMM can use such calibration data they must be
entered into a specially formatted text file and registered with the project. Calibration Files Calibration Files contain measurements of a single parameter at one or more locations that can
be compared with simulated values in Time Series Plots. Separate files can be used for each of
the following parameters:
 Subcatchment Runoff
 Subcatchment Pollutant Washoff
 Groundwater Flow
 Groundwater Elevation
 Snow Pack Depth
 Node Depth
 Node Lateral Inflow
 Node Flooding
 Node Water Quality
 Link Flow Rate
 Link Flow Depth
 Link Flow Velocity
The format of the file is described in Section 11.5. Registering Calibration Data To register calibration data residing in a Calibration File:
  1. Select Project >> Calibration Data from the Main Menu.
  2. In the Calibration Data dialog form shown below, click in the box next to the parameter
    (e.g., node depth, link flow, etc.) whose calibration data will be registered.
  3. Either type in the name of a Calibration File for this parameter or click the Browse button
    to search for it.
  4. Click the Edit button if you want to open the Calibration File in Windows NotePad for
    editing.
  5. Repeat steps 2 – 4 for any other parameters that have calibration data.
  6. Click OK to accept your selections.

5.8 Viewing All Project Data

A listing of all project data (with the exception of map coordinates) can be viewed in a non-
editable window, formatted for input to SWMM’s computational engine (see below). This can be
useful for checking data consistency and to make sure that no key components are missing. To
view such a listing select Project >> Details from the Main Menu. The format of the data in this
listing is the same as that used when the file is saved to disk. It is described in detail in Appendix
D.2.

CHAPTER 6 – WORKING WITH OBJECTS

SWMM uses various types of objects to model a drainage area and its conveyance system. This
section describes how these objects can be created, selected, edited, deleted, and repositioned.

6.1 Types of Objects

SWMM contains both physical objects that can appear on its Study Area Map, and non-physical
objects that encompass design, loading, and operational information. These objects, which are
listed in the Project Browser and were described in Chapter 3, consist of the following:
Project Title/Notes Nodes
Simulation Options Links
Climatology Transects
Rain Gages Control Rules
Subcatchments Pollutants
Aquifers Land Uses
Snow Packs Curves
Unit Hydrographs Time Series
LID Controls Time Patterns
Map Labels

6.2 Adding Objects

To add a new object to a project, select the type of object from the upper pane of the Project
Browser and either select Project >> Add a New … from the Main Menu or click the Browser’s button. If the object has a button on the Object Toolbar you can simply click the toolbar button
instead. If the object is a visual object that appears on the Study Area Map (a Rain Gage, Subcatchment,
Node, Link, or Map Label) it will automatically receive a default ID name and a prompt will appear
in the Status Bar telling you how to proceed. The steps used to draw each of these objects on the
map are detailed below: Rain Gages Move the mouse to the desired location on the Map and left-click. Subcatchments Use the mouse to draw a polygon outline of the subcatchment on the Map:
  • left-click at each vertex
  • right-click or press to close the polygon
  • press the key if you wish to cancel the action.
Nodes (Junctions, Outfalls, Flow Dividers, and Storage Units) Move the mouse to the desired location on the Study Area Map and left-click. Links (Conduits, Pumps, Orifices, Weirs, and Outlets)
  • Left-click the mouse on the link’s inlet (upstream) node.
  • Move the mouse (without pressing any button) in the direction of the link’s outlet
    (downstream) node, clicking at all intermediate points necessary to define the link’s
    alignment.
  • Left-click the mouse a final time over the link’s outlet (downstream) node. (Pressing the right
    mouse button or the key while drawing a link will cancel the operation.)
Map Labels
  • Left-click the mouse on the map location where the top left corner of the label should appear.
  • Enter the text for the label.
  • Press to accept the label or to cancel.
For all other non-visual types of objects, an object-specific dialog form will appear that allows you
to name the object and edit its properties.

6.3 Selecting and Moving Objects

To select an object on the map:
  1. Make sure that the map is in Selection mode (the mouse cursor has the shape of an
    arrow pointing up to the left). To switch to this mode, either click the Select Object button
    on the Map Toolbar or choose Edit >> Select Object from the Main Menu.
  2. Click the mouse over the desired object on the map.
To select an object using the Project Browser:
  1. Select the object’s category from the upper list in the Browser.
  2. Select the object from the lower list in the Browser.
Rain gages, subcatchments, nodes, and map labels can be moved to another location on the
Study Area Map. To move an object to another location:
  1. Select the object on the map.
  2. With the left mouse button held down over the object, drag it to its new location.
  3. Release the mouse button.
The following alternative method can also be used:
  1. Select the object to be moved from the Project Browser (it must either be a rain gage,
    subcatchment, node, or map label).
  2. With the left mouse button held down, drag the item from the Items list box of the Data
    Browser to its new location on the map.
  3. Release the mouse button.
Note that the second method can be used to place objects on the map that were imported from a
project file that had no coordinate information included in it.

6.4 Editing Objects

To edit an object appearing on the Study Area Map:
  1. Select the object on the map.
  2. If the Property Editor is not visible either:
     double click on the object
     or right-click on the object and select Properties from the pop-up menu that appears
     or click on in the Project Browser
     or select Edit >> Edit Object from the Main Menu.
  3. Edit the object’s properties in the Property Editor.
Appendix B lists the properties associated with each of SWMM’s visual objects. To edit an object listed in the Project Browser:
  1. Select the object in the Project Browser.
  2. Either:
 click on in the Project Browser,
 or select Edit >> Edit Object from the Main Menu,
 or double-click the item in the Objects list,
 or press the <Enter> key.
Depending on the class of object selected, a special property editor will appear in which the
object’s properties can be modified. Appendix C describes all of the special property editors used
with SWMM’s non-visual objects.
The unit system in which object properties are expressed depends on the choice of units
for flow rate. Using a flow rate expressed in cubic feet, gallons or acre-feet implies that
US units will be used for all quantities. Using a flow rate expressed in liters or cubic
meters means that SI metric units will be used. Flow units are selected either from the
project’s default Node/Link properties (see Section5.4) or directly from the main window’s
Status Bar (see Section 4.4). The units used for all properties are listed in Appendix A.1.

6.5 Converting an Object

It is possible to convert a node or link from one type to another without having to first delete the
object and add a new one in its place. An example would be converting a Junction node into an
Outfall node, or converting an Orifice link into a Weir link. To convert a node or link to another
type:
  1. Right-click the object on the map.
  2. Select Convert To from the popup menu that appears.
  3. Select the new type of node or link to convert to from the sub-menu that appears.
  4. Edit the object to provide any data that was not included with the previous type of object.
Only data that is common to both types of objects will be preserved after an object is converted to
a different type. For nodes this includes its name, position, description, tag, external inflows,
treatment functions, and invert elevation. For links it includes just its name, end nodes,
description, and tag.

6.6 Copying and Pasting Objects

The properties of an object displayed on the Study Area Map can be copied and pasted into
another object from the same category. To copy the properties of an object to SWMM’s internal clipboard:
  1. Right-click the object on the map.
  2. Select Copy from the pop-up menu that appears.
To paste copied properties into an object:
  1. Right-click the object on the map.
  2. Select Paste from the pop-up menu that appears.
Only data that can be shared between objects of the same type can be copied and pasted.
Properties not copied include the object’s name, coordinates, end nodes (for links), tag property
and any descriptive comment associated with the object. For Map Labels, only font properties are
copied and pasted.

6.7 Shaping and Reversing Links

Links can be drawn as polylines containing any number of straight-line segments that define the
alignment or curvature of the link. Once a link has been drawn on the map, interior points that
define these line segments can be added, deleted, and moved. To edit the interior points of a link:
  1. Select the link to edit on the map and put the map in Vertex Selection mode either by
    clicking on the Map Toolbar, selecting Edit >> Select Vertex from the Main Menu, or
    right clicking on the link and selecting Vertices from the popup menu.
  2. The mouse pointer will change shape to an arrow tip, and any existing vertex points on
    the link will be displayed as small open squares. The currently selected vertex will be
    displayed as a filled square. To select a particular vertex, click the mouse over it.
  3. To add a new vertex to the link, right-click the mouse and select Add Vertex from the
    popup menu (or simply press the key on the keyboard).
  4. To delete the currently selected vertex, right-click the mouse and select Delete Vertex
    from the popup menu (or simply press the key on the keyboard).
  5. To move a vertex to another location, drag it to its new position with the left mouse button
    held down.
While in Vertex Selection mode you can begin editing the vertices for another link by simply
clicking on the link. To leave Vertex Selection mode, right-click on the map and select Quit
Editing from the popup menu, or simply select one of the other buttons on the Map Toolbar. A link can also have its direction reversed (i.e., its end nodes switched) by right clicking on it and
selecting Reverse from the pop-up menu that appears. Normally, links should be oriented so that
the upstream end is at a higher elevation than the downstream end.

6.8 Shaping a Subcatchment

Subcatchments are drawn on the Study Area Map as closed polygons. To edit or add vertices to
the polygon, follow the same procedures used for links. If the subcatchment is originally drawn or
is edited to have two or less vertices, then only its centroid symbol will be displayed on the Study
Area Map.

6.9 Deleting an Object

To delete an object:
  1. Select the object on the map or from the Project Browser.
  2. Either click the button on the Project Browser or press the key on the
    keyboard, or select Edit >> Delete Object from the Main Menu, or right-click the object
    on the map and select Delete from the pop-up menu that appears.
You can require that all deletions be confirmed before they take effect. See the General
Preferences page of the Program Preferences dialog box described in Section 4.9.

6.10 Editing or Deleting a Group of Objects

A group of objects located within an irregular region of the Study Area Map can have a common
property edited or be deleted all together. To select such a group of objects:
  1. Choose Edit >> Select Region from the Main Menu or click on the Map Toolbar.
  2. Draw a polygon around the region of interest on the map by clicking the left mouse button
    at each successive vertex of the polygon.
  3. Close the polygon by clicking the right button or by pressing the key; cancel the
    selection by pressing the key.
To select all objects in the project, whether in view or not, select Edit >> Select All from the Main
Menu. Once a group of objects has been selected, you can edit a common property shared among
them:
  1. Select Edit >> Group Edit from the Main Menu.
  2. Use the Group Editor dialog that appears to select a property and specify its new value.
The Group Editor dialog, shown below, is used to modify a property for a selected group of
objects. To use the dialog:
  1. Select a type of object (Subcatchments, Infiltration, Junctions, Storage Units, or
    Conduits) to edit.
  2. Check the “with Tag equal to” box if you want to add a filter that will limit the objects
    selected for editing to those with a specific Tag value. (For Infiltration, the Tag will be that
    of the subcatchment to which the infiltration parameters belong.)
  3. Enter a Tag value to filter on if you have selected that option.
  4. Select the property to edit.
  5. Select whether to replace, multiply, or add to the existing value of the property. Note that
    for some non-numerical properties the only available choice is to replace the value.
  6. In the lower-right edit box, enter the value that should replace, multiply, or be added to
    the existing value for all selected objects. Some properties will have an ellipsis button
displayed in the edit box which should be clicked to bring up a specialized editor for the
property.
  1. Click OK to execute the group edit.
After the group edit is executed a confirmation dialog box will appear informing you of how many
items were modified. It will ask if you wish to continue editing or not. Select Yes to return to the
Group Edit dialog box to edit another parameter or No to dismiss the Group Edit dialog. To delete the objects located within a selected area of the map, select Edit >> Group Delete
from the Main Menu. Then select the categories of objects you wish to delete from the dialog box
that appears. As an option, you can specify that only objects within the selected area that have a
specific Tag property should be deleted. Keep in mind that deleting a node will also delete any
links connected to the node.

CHAPTER 7 – WORKING WITH THE MAP

EPA SWMM can display a map of the study area being modeled. This section describes how you
can manipulate this map to enhance your visualization of the system.

7.1 Selecting a Map Theme

A map theme displays object properties in color-coded fashion on the Study Area Map. The
dropdown list boxes on the Map Browser are used for selecting a theme to display for
Subcatchments, Nodes and Links. Methods for changing the color-coding associated with a theme are discussed in Section 7. 10
below.

7.2 Setting the Map’s Dimensions

The physical dimensions of the map can be defined so that map coordinates can be properly
scaled to the computer’s video display. To set the map’s dimensions:
  1. Select View >> Dimensions from the Main Menu.
  2. Enter coordinates for the lower-left and upper-right corners of the map into the Map
    Dimensions dialog (see below) that appears or click the Auto-Size button to automatically
    set the dimensions based on the coordinates of the objects currently included in the map.
  3. Select the distance units to use for these coordinates.
  4. If the Auto-Length option is in effect, check the “Re-compute all lengths and areas” box
    if you would like SWMM to re-calculate all conduit lengths and subcatchment areas under
    the new set of map dimensions.
  5. Click the OK button to resize the map.
If you are going to use a backdrop image with the automatic distance and area
calculation feature, then it is recommended that you set the map dimensions immediately
after creating a new project. Map distance units can be different from conduit length units.
The latter (feet or meters) depend on whether flow rates are expressed in US or metric
units. SWMM will automatically convert units if necessary.
If you just want to re-compute conduit lengths and subcatchment areas without changing
the map's dimensions, then just check the Re-compute Lengths and Areas box and leave
the coordinate boxes as they are.

7.3 Utilizing a Backdrop Image

SWMM can display a backdrop image behind the Study Area Map. The backdrop image might be
a street map, utility map, topographic map, site development plan, or any other relevant picture or
drawing. For example, using a street map would simplify the process of adding sewer lines to the
project since one could essentially digitize the drainage system’s nodes and links directly on top
of it. The backdrop image must be a Windows metafile, bitmap, or JPEG image created outside of
SWMM. Once imported, its features cannot be edited, although its scale and viewing area will
change as the map window is zoomed and panned. For this reason metafiles work better than
bit maps or JPEGs since they will not lose resolution when re-scaled. Most CAD and GIS
programs have the ability to save their drawings and maps as metafiles. Selecting View >> Backdrop from the Main Menu will display a sub-menu with the following
commands:
 Load (loads a backdrop image file into the project)
 Unload (unloads the backdrop image from the project)
 Align (aligns the drainage system schematic with the backdrop)
 Resize (resizes the map dimensions of the backdrop)
 Watermark (toggles the backdrop image appearance between normal and lightened)
To load a backdrop image select View >> Backdrop >> Load from the Main Menu. A Backdrop
Image Selector dialog form will be displayed. The entries on this form are as follows: Backdrop Image File Enter the name of the file that contains the image. You can click the button to bring up a
standard Windows file selection dialog from which you can search for the image file. World Coordinates File If a “world” file exists for the image, enter its name here, or click the button to search for it. A
world file contains geo-referencing information for the image and can be created from the
software that produced the image file or by using a text editor. It contains six lines with the
following information: Line 1: real world width of a pixel in the horizontal direction. Line 2: X rotation parameter (not used). Line 3: Y rotation parameter (not used). Line 4: negative of the real world height of a pixel in the vertical direction. Line 5: real world X coordinate of the upper left corner of the image. Line 6: real world Y coordinate of the upper left corner of the image. If no world file is specified, then the backdrop will be scaled to fit into the center of the map
display window. Scale Map to Backdrop Image This option is only available when a world file has been specified. Selecting it forces the
dimensions of the Study Area Map to coincide with those of the backdrop image. In addition, all
existing objects on the map will have their coordinates adjusted so that they appear within the
new map dimensions yet maintain their relative positions to one another. Selecting this option
may then require that the backdrop be re-aligned so that its position relative to the drainage area
objects is correct. How to do this is described below. The backdrop image can be re-positioned relative to the drainage system by selecting View >>
Backdrop >> Align. This allows the backdrop image to be moved across the drainage system
(by moving the mouse with the left button held down) until one decides that it lines up properly. The backdrop image can also be resized by selecting View >> Backdrop >> Resize. In this case
the following Backdrop Dimensions dialog will appear. The dialog lets you manually enter the X,Y coordinates of the backdrop’s lower left and upper
right corners. The Study Area Map’s dimensions are also displayed for reference. While the
dialog is visible you can view map coordinates by moving the mouse over the map window and
noting the X,Y values displayed in SWMM’s Status Panel (at the bottom of the main window).
Selecting the Resize Backdrop Image Only button will resize only the backdrop, and not the
Study Area Map, according to the coordinates specified. Selecting the Scale Backdrop Image to
Map b utton will position the backdrop image in the center of the Study Area Map and have it
resized to fill the display window without changing its aspect ratio. The map’s lower left and upper
right coordinates will be placed in the data entry fields for the backdrop coordinates, and these
fields will become disabled. Selecting Scale Map to Backdrop Image makes the dimensions of
the map coincide with the dimensions being set for the backdrop image. Note that this option will
change the coordinates of all objects currently on the map so that their positions relative to one
another remain unchanged. Selecting this option may then require that the backdrop be re-
aligned so that its position relative to the drainage area objects is correct.
Exercise caution when selecting the Scale Map to Backdrop Image option in either the
Backdrop Image Selector dialog or the Backdrop Dimensions dialog as it will modify the
coordinates of all existing objects currently on the Study Area Map. You might want to
save your project before carrying out this step in case the results are not what you
expected.
The name of the backdrop image file and its map dimensions are saved along with the rest of a
project’s data whenever the project is saved to file. For best results in using a backdrop image:
 Use a metafile, not a bitmap.
 If the image is loaded before any objects are added to the project then scale the map to
it.

7.4 Measuring Distances

To measure a distance or area on the Study Area Map:
  1. Click on the Map Toolbar.
  2. Left-click on the map where you wish to begin measuring from.
  3. Move the mouse over the distance being measured, left-clicking at each intermediate
    location where the measured path changes direction.
  4. Right-click the mouse or press to complete the measurement.
  5. The distance measured in project units (feet or meters) will be displayed in a dialog box.
    If the last point on the measured path coincides with the first point then the area of the
    enclosed polygon will also be displayed.

7.5 Zooming the Map

To Zoom In on the Study Area Map:
  1. Select View >> Zoom In from the Main Menu or click on the Map Toolbar.
  2. To zoom in 100% (i.e., 2X), move the mouse to the center of the zoom area and click the
    left button.
  3. To perform a custom zoom, move the mouse to the upper left corner of the zoom area
    and with the left button pressed down, draw a rectangular outline around the zoom area.
    Then release the left button.
To Zoom Out on the Study Area Map:
  1. Select View >> Zoom Out from the Main Menu or click on the Map Toolbar.
  2. The map will be returned to the view in effect at the previous zoom level.

7.6 Panning the Map

To pan across the Study Area Map window:
  1. Select View >> Pan from the Main Menu or click on the Map Toolbar.
  2. With the left button held down over any point on the map, drag the mouse in the direction
    you wish to pan in.
  3. Release the mouse button to complete the pan.
To pan using the Overview Map (which is described in Section 7.11 below):
  1. If not already visible, bring up the Overview Map by selecting View >> Overview Map
    from the Main Menu or click the button on the Standard Toolbar.
  2. If the Study Area Map has been zoomed in, an outline of the current viewing area will
    appear on the Overview Map. Position the mouse within this outline on the Overview
    Map.
  3. With the left button held down, drag the outline to a new position.
  4. Release the mouse button and the Study Area Map will be panned to an area
    corresponding to the outline on the Overview Map.

7.7 Viewing at Full Extent

To view the Study Area Map at full extent, either:
 select View >> Full Extent from the Main Menu, or
 press on the Map Toolbar.

7.8 Finding an Object

To find an object on the Study Area Map whose name is known:
  1. Select View >> Find Object from the Main Menu or click on the Standard Toolbar.
  2. In the Map Finder dialog that appears, select the type of object to find and enter its name.
  3. Click the Go button.
If the object exists, it will be highlighted on the map and in the Data Browser. If the map is
currently zoomed in and the object falls outside the current map boundaries, the map will be
panned so that the object comes into view.
User-assigned object names in SWMM are not case sensitive. E.g., NODE123 is
equivalent to Node123.
After an object is found, the Map Finder dialog will also list:
 the outlet connections for a subcatchment
 the connecting links for a node
 the connecting nodes for a link.

7.9 Submitting a Map Query

A Map Query identifies objects on the study area map that meet a specific criterion (e.g., nodes
which flood, links with velocity below 2 ft/sec, etc.). It can also identify which subcatchments have
LID controls and which nodes have external inflows. To submit a map query:
  1. Select a time period in which to query the map from the Map Browser.
  2. Select View >> Query or click on the Standard Toolbar.
  3. Fill in the following information in the Query dialog that appears:
     Select whether to search for Subcatchments, Nodes, Links, LID Subcatchments or
    Inflow Nodes.
     Select a parameter to query or the type of LID or inflow to locate.
     Select the appropriate operator: Above, Below, or Equals.
     Enter a value to compare against.
  4. Click the Go button. The number of objects that meet the criterion will be displayed in the
    Query dialog and each such object will be highlighted on the Study Area Map.
  5. As a new time period is selected in the Browser, the query results are automatically
    updated.
  6. You can submit another query using the dialog box or close it by clicking the button in the
    upper right corner.
After the Query box is closed the map will revert back to its original display.

7.10 Using the Map Legends

Map Legends associate a color with a range of values for the current
theme being viewed. Separate legends exist for Subcatchments, Nodes,
and Links. A Date/Time Legend is also available for displaying the date
and clock time of the simulation period being viewed on the map.
To display or hide a map legend:
  1. Select View >> Legends from the Main Menu or right-click on the map and select
    Legends from the pop-up menu that appears
  2. Click on the type of legend whose display should be toggled on or off.
A visible legend can also be hidden by double clicking on it. To move a legend to another location press the left mouse button over the legend, drag the
legend to its new location with the button held down, and then release the button. To edit a legend, either select View >> Legends >> Modify from the Main Menu or right-click on
the legend if it is visible. Then use the Legend Editor dialog that appears to modify the legend’s
colors and intervals. The Legend Editor is used to set numerical ranges to which different colors are assigned for
viewing a particular parameter on the network map. It works as follows:
 Numerical values, in increasing order, are entered in the edit boxes to define the ranges.
Not all four boxes need to have values.
 To change a color, click on its color band in the Editor and then select a new color from
the Color Dialog that will appear.
 Click the Auto-Scale button to automatically assign ranges based on the minimum and
maximum values attained by the parameter in question at the current time period.
 The Color Ramp button is used to select from a list of built-in color schemes.
 The Reverse Colors button reverses the ordering of the current set of colors (the color in
the lowest range becomes that of the highest range and so on).
 Check Framed if you want a frame drawn around the legend.
Changes made to a legend are saved with the project’s settings and remain in effect when the
project is re-opened in a subsequent session.

7.11 Using the Overview Map

The Overview Map, as pictured below, allows one to see where in terms of the overall system the
main Study Area Map is currently focused. This zoom area is depicted by the rectangular outline
displayed on the Overview Map. As you drag this rectangle to another position the view within the
main map will be redrawn accordingly. The Overview Map can be toggled on and off by selecting View >> Overview Map from the Main Menu or by clicking on the Standard Toolbar. The
Overview Map window can also be dragged to any position as well as be re-sized.

7.12 Setting Map Display Options

The Map Options dialog (shown below) is used to change the appearance of the Study Area Map.
There are several ways to invoke it:
 select Tools >> Map Display Options from the Main Menu or,
 click the Options button on the Standard Toolbar when the Study Area Map window
has the focus or,
 right-click on any empty portion of the map and select Options from the popup menu that
appears.
The dialog contains a separate page, selected from the panel on the left side of the form, for each
of the following display option categories:
 Subcatchments (controls fill style, symbol size, and outline thickness of subcatchment
areas)
 Nodes (controls size of nodes and making size be proportional to value)
 Links (controls thickness of links and making thickness be proportional to value)
 Labels (turns display of map labels on/off)
 Annotation (displays or hides node/link ID labels and parameter values)
 Symbols (turns display of storage unit, pump, and regulator symbols on/off)
 Flow Arrows (selects visibility and style of flow direction arrows)
 Background (changes color of map's background).
Subcatchment Options The Subcatchments page of the Map Options dialog controls how subcatchment areas are
displayed on the study area map.
Option Description
Fill Style Selects style used to fill interior of subcatchment area
Symbol Size Sets the size of the symbol (in pixels) placed at the centroid of a
subcatchment area
Border Size Sets the thickness of the line used to draw a subcatchment's
border; if set to zero then only the subcatchment centroid will be
displayed
Display Link to
Outlet
If checked then a dashed line is drawn between the subcatchment
centroid and the subcatchment's outlet node (or outlet
subcatchment)
Node Options The Nodes page of the Map Options dialog controls how nodes are displayed on the study area
map.
Option Description
Node Size Selects node diameter in pixels
Proportional to
Value
Select if node size should increase as the viewed parameter
increases in value
Display Border Select if a border should be drawn around each node
(recommended for light-colored backgrounds)
Link Options The Links page of the Map Options dialog controls how links are displayed on the map.
Option Description
Link Size Sets thickness of links displayed on map (in pixels)
Proportional to
Value
Select if link thickness should increase as the viewed parameter
increases in value
Display Border Check if a black border should be drawn around each link
Label Options The Labels page of the Map Options dialog controls how user-created map labels are displayed
on the study area map.
Option Description
Use Transparent
Text
Check to display label with a transparent background (otherwise
an opaque background is used)
At Zoom Of Selects minimum zoom at which labels should be displayed;
labels will be hidden at zooms smaller than this
Annotation Options The Annotation page of the Map Options dialog form determines what kind of annotation is
provided alongside of the objects on the study area map.
Option Description
Rain Gage IDs Check to display rain gage ID names
Subcatch IDs Check to display subcatchment ID names
Node IDs Check to display node ID names
Link IDs Check to display link ID names
Subcatch Values Check to display value of current subcatchment variable
Node Values Check to display value of current node variable
Link Values Check to display value of current link variable
Use Transparent Text Check to display text with a transparent background
(otherwise an opaque background is used)
Font Size Adjusts the size of the font used to display annotation^
At Zoom Of Selects minimum zoom at which annotation should be
displayed; all annotation will be hidden at zooms smaller
than this
Symbol Options The Symbols page of the Map Options dialog determines which types of objects are represented
with special symbols on the map.
Option Description
Display Node Symbols If checked then special node symbols will be used
Display Link Symbols If checked then special link symbols will be used
At Zoom Of Selects minimum zoom at which symbols should be
displayed; symbols will be hidden at zooms smaller than this
Flow Arrow Options The Flow Arrows page of the Map Options dialog controls how flow-direction arrows are
displayed on the map.
Option Description
Arrow Style Selects style (shape) of arrow to display (select None to hide
arrows)
Arrow Size Sets arrow size
At Zoom Of Selects minimum zoom at which arrows should be displayed;
arrows will be hidden at zooms smaller than this
Flow direction arrows will only be displayed after a successful simulation has been made
and a computed parameter has been selected for viewing. Otherwise the direction arrow
will point from the user-designated start node to end node.
Background Options The Background page of the Map Options dialog offers a selection of colors used to paint the
map’s background with.

7.13 Exporting the Map

The full extent view of the study area map can be saved to file using either:
 Autodesk's DXF (Drawing Exchange Format) format,
 the Windows enhanced metafile (EMF) format,
 EPA SWMM's own ASCII text (.map) format.
The DXF format is readable by many Computer Aided Design (CAD) programs. Metafiles can be
inserted into word processing documents and loaded into drawing programs for re-scaling and
editing. Both formats are vector-based and will not lose resolution when they are displayed at
different scales. To export the map to a DXF, metafile, or text file:
  1. Select File >> Export >> Map.
  2. In the Map Export dialog that appears select the format that you want the map saved in.
If you select DXF format, you have a choice of how nodes will be represented in the DXF file.
They can be drawn as filled circles, as open circles, or as filled squares. Not all DXF readers can
recognize the format used in the DXF file to draw a filled circle. Also note that map annotation,
such as node and link ID labels will not be exported, but map label objects will be. After choosing a format, click OK and enter a name for the file in the Save As dialog that appears.

CHAPTER 8 – RUNNING A SIMULATION

After a study area has been suitably described, its runoff response, flow routing and water quality
behavior can be simulated. This section describes how to specify options to be used in the
analysis, how to run the simulation and how to troubleshoot common problems that might occur.

8.1 Setting Simulation Options

SWMM has a number of options that control how the simulation of a stormwater drainage system
is carried out. To set these options:
  1. Select the Options category from the Project Browser.
  2. Select one of the following categories of options to edit:
    a. General Options
    b. Date Options
    c. Time Step Options
    d. Dynamic Wave Routing Options
    e. Interface File Options
    f. Reporting Options
  3. Click the button on the Browser panel or select Edit >> Edit Object to invoke the
    appropriate editor for the chosen option category (the Simulation Options dialog is used
    for the first five categories while the Reporting Options dialog is used for the last one).
The Simulations Options dialog contains a separate tabbed page for each of the first five option
categories listed above. Each page is described in more detail below. 8.1.1 General Options The General page of the Simulation Options dialog sets values for the following options: Process Models This section allows you to select which of SWMM’s process models will be applied to the current
project. For example, a model that contained Aquifer and Groundwater elements could be run
first with the groundwater computations turned on and then again with them turned off to see
what effect this process had on the site’s hydrology. Note that if there are no elements in the
project needed to model a given process then that process option is disabled (e.g., if there were
no Aquifers defined for the project then the Groundwater check box will appear disabled in an
unchecked state). Infiltration Model This option controls how infiltration of rainfall into the upper soil zone of subcatchments is
modeled. The choices are:
 Horton
 Modified Horton
 Green-Ampt
 Modified Green-Ampt
 Curve Number
Each of these models is briefly described in section 3.4.2. Changing this option will require re-
entering values for the infiltration parameters in each subcatchment, unless the change is
between the two Horton options or the two Green-Ampt options. Routing Model This option determines which method is used to route flows through the conveyance system. The
choices are:
 Steady Flow
 Kinematic Wave
 Dynamic Wave
Review section 3.4.5 for a brief description of each of these alternatives. Allow Ponding Checking this option will allow excess water to collect atop nodes and be re-introduced into the
system as conditions permit. In order for ponding to actually occur at a particular node, a non-
zero value for its Ponded Area attribute must be used. Report Control Actions Check this option if you want the simulation’s Status Report to list all discrete control actions
taken by the Control Rules associated with a project (continuous modulated control actions are
not listed). This option should only be used for short-term simulation. Report Input Summary Check this option if you want the simulation’s Status Report to list a summary of the project’s
input data. Minimum Conduit Slope The minimum value allowed for a conduit’s slope (%). If blank or zero (the default) then no
minimum is imposed (although SWMM uses a lower limit on elevation drop of 0.001 ft (0.00035
m) when computing a conduit slope). 8.1.2 Date Options The Dates page of the Simulation Options dialog determines the starting and ending dates/times
of a simulation. Start Analysis On Enter the date (month/day/year) and time of day when the simulation begins. Start Reporting On Enter the date and time of day when reporting of simulation results is to begin. Using a date prior
to the start date is the same as using the start date. End Analysis On Enter the date and time when the simulation is to end. Start Sweeping On
Enter the day of the year (month/day) when street sweeping operations begin. The default is
January 1. End Sweeping On Enter the day of the year (month/day) when street sweeping operations end. The default is
December 31. Antecedent Dry Days Enter the number of days with no rainfall prior to the start of the simulation. This value is used to
compute an initial buildup of pollutant load on the surface of subcatchments.
If rainfall or climate data are read from external files, then the simulation dates should be
set to coincide with the dates recorded in these files.
8.1.3 Time Step Options The Time Steps page of the Simulation Options dialog establishes the length of the time steps
used for runoff computation, routing computation and results reporting. Time steps are specified
in days and hours:minutes:seconds except for flow routing which is entered as decimal seconds. Reporting Time Step Enter the time interval for reporting of computed results. Runoff – Wet Weather Time Step Enter the time step length used to compute runoff from subcatchments during periods of rainfall,
or when ponded water still remains on the surface, or when LID controls are still infiltrating or
evaporating runoff. Runoff – Dry Weather Time Step Enter the time step length used for runoff computations (consisting essentially of pollutant
buildup) during periods when there is no rainfall, no ponded water, and LID controls are dry. This
must be greater or equal to the Wet Weather time step. Routing Time Step Enter the time step length in decimal seconds used for routing flows and water quality
constituents through the conveyance system. Note that Dynamic Wave routing requires a much
smaller time step than the other methods of flow routing. Steady Flow Periods This set of options tells SWMM how to identify and treat periods of time when system hydraulics
is not changing. The system is considered to be in a steady flow period if:
  • The percent difference between total system inflow and total system outflow is below the
    System Flow Tolerance,
  • The percent differences between the current lateral inflow and that from the previous time
    step for all points in the conveyance system are below the Lateral Flow Tolerance.
Checking the Skip Steady Flow Periods box will make SWMM keep using the most recently
computed conveyance system flows (instead of computing a new flow solution) whenever the
above criteria are met. Using this feature can help speed up simulation run times at the expense
of reduced accuracy. 8.1.4 Dynamic Wave Options The Dynamic Wave page of the Simulation Options dialog sets several parameters that control
how the dynamic wave flow routing computations are made. These parameters have no effect for
the other flow routing methods. Inertial Terms Indicates how the inertial terms in the St. Venant momentum equation will be handled.
 KEEP maintains these terms at their full value under all conditions.
 DAMPEN reduces the terms as flow comes closer to being critical and ignores them
when flow is supercritical.
 IGNORE drops the terms altogether from the momentum equation, producing what is
essentially a Diffusion Wave solution.
Define Supercritical Flow By Selects the basis used to determine when supercritical flow occurs in a conduit. The choices are:
 water surface slope only (i.e., water surface slope > conduit slope)
 Froude number only (i.e., Froude number > 1.0)
 both water surface slope and Froude number.
The first two choices were used in earlier versions of SWMM while the third choice, which checks
for either condition, is now the recommended one. Force Main Equation Selects which equation will be used to compute friction losses during pressurized flow for
conduits that have been assigned a Circular Force Main cross-section. The choices are either the
Hazen-Williams equation or the Darcy-Weisbach equation. Use Variable Time Steps Check the box if an internally computed variable time step should be used at each routing time
period and select an adjustment (or safety) factor to apply to this time step. The variable time step
is computed so as to satisfy the Courant condition within each conduit. A typical adjustment factor
would be 75% to provide some margin of conservatism. The computed variable time step will not be less than the minimum variable step discussed below nor be greater than the fixed time step
specified on the Time Steps page of the dialog. Minimum Variable Time Step This is the smallest time step allowed when variable time steps are used. The default value is 0.5
seconds. Smaller steps may be warranted, but they can lead to longer simulations runs without
much improvement in solution quality. Time Step for Conduit Lengthening This is a time step, in seconds, used to artificially lengthen conduits so that they meet the Courant
stability criterion under full- flow conditions (i.e., the travel time of a wave will not be smaller than
the specified conduit lengthening time step). As this value is decreased, fewer conduits will
require lengthening. A value of zero means that no conduits will be lengthened. The ratio of the
artificial length to the original length for each conduit is listed in the Flow Classification t able that
appears in the simulation’s Summary Report (see Section 9.2). Minimum Nodal Surface Area This is a minimum surface area used at nodes when computing changes in water depth. If 0 is
entered, then the default value of 12.566 ft^2 (1.167 m^2 ) is used. This is the area of a 4- ft diameter
manhole. The value entered should be in square feet for US units or square meters for SI units. Maximum Trials per Time Step This is the maximum number of trials that SWMM uses at each time step to reach convergence
when updating hydraulic heads at the conveyance system’s nodes. The default value is 8. Head Convergence Tolerance When the difference in computed head at each node between successive trials is below this
value the flow solution for the current time step is assumed to have converged. The default
tolerance is 0.005 ft (0.0015 m). Number of Threads This selects the number of parallel computing threads to use on machines equipped with multi-
core processors. The default is 1. Clicking the Apply Defaults label will set all the Dynamic Wave options to their default values. 8.1.5 File Options The Files page of the Simulation Options dialog is used to specify which interface files will be
used or saved during the simulation. (Interface files are described in Chapter 11.) The page
contains a list box with three buttons underneath it. The list box lists the currently selected files,
while the buttons are used as follows: Add adds a new interface file specification to the list. Edit edits the properties of the currently selected interface file. Delete deletes the currently selected interface from the project (but not from your hard drive). When the Add or Edit buttons are clicked, an Interface File Selector dialog appears where you
can specify the type of interface file, whether it should be used or saved, and its name. The
entries on this dialog are as follows: File Type Select the type of interface file to be specified. Use / Save Buttons Select whether the named interface file will be used to supply input to a simulation run or whether
simulation results will be saved to it. File Name Enter the name of the interface file or click the Browse button to select from a standard
Windows file selection dialog box.

8.2 Setting Reporting Options

The Reporting Options dialog is used to select individual subcatchments, nodes, and links that
will have detailed time series results saved for viewing after a simulation has been run. The
default for new projects is that all objects will have detailed results saved for them. The dialog is
invoked by selecting the Reporting category of Options from the Project Browser and clicking the
button (or by selecting Edit >> Edit Object from the main menu).
The dialog contains three tabbed pages – one each for subcatchments, nodes, and links. It is a
stay-on-top form which means that you can select items directly from the Study Area Map or
Project Browser while the dialog remains visible. To include an object in the set that is reported on:
  1. Select the tab to which the object belongs (Subcatchments, Nodes or Links).
  2. Unselect the “All” check box if it is currently checked.
  3. Select the specific object either from the Study Area Map or from the listing in the
    Project Browser.
  4. Click the Add button on the dialog.
  5. Repeat the above steps for any additional objects.
To remove an item from the set selected for reporting:
  1. Select the desired item in the dialog’s list box.
  2. Click the Remove button to remove the item.
To remove all items from the reporting set of a given object category, select the object category’s
page and click the Clear button. To include all objects of a given category in the reporting set, check the “All” box on the page for
that category (i.e., subcatchments, nodes, or links). This will override any individual items that
may be currently listed on the page. To dismiss the dialog click the Close button.

8.3 Starting a Simulation

To start a simulation either select Project >> Run Simulation from the Main Menu or click on
the Standard Toolbar. A Run Status window will appear which displays the progress of the
simulation. To stop a run before its normal termination, click the Stop button on the Run Status window or
press the key. Simulation results up until the time when the run was stopped will be
available for viewing. To minimize the SWMM program while a simulation is running, click the
Minimize button on the Run Status window. If the analysis runs successfully the icon will appear in the Run Status section of the Status
Bar at the bottom of SWMM’s main window. Any error or warning messages will appear in a
Status Report window. If you modify the project after a successful run has been made, the status flag changes to indicating that the current computed results no longer apply to the modified
project.

8.4 Troubleshooting Results

When a run ends prematurely, the Run Status dialog will indicate the run was unsuccessful and
direct the user to the Status Report for details. The Status Report will include an error statement,
code, and description of the problem (e.g., ERROR 138: Node TG040 has initial depth greater
than maximum depth). Consult Appendix E for a description of SWMM’s error messages. Even if
a run completes successfully, one should check to insure that the results are reasonable. The
following are the most common reasons for a run to end prematurely or to contain questionable
results. Unknown ID Error Message This message typically appears when an object references another object that was never defined.
An example would be a subcatchment whose outlet was designated as N29, but no such
subcatchment or node with that name exists. Similar situations can exist for incorrect references
made to Curves, Time Series, Time Patterns, Aquifers, Snow Packs, Transects, Pollutants, and
Land Uses. File Errors File errors can occur when:
 a file cannot be located on the user's computer
 a file being used has the wrong format
 a file being written cannot be opened because the user does not have write privileges for
the directory (folder) where the file is to be stored.
Drainage System Layout Errors A valid drainage system layout must obey the following conditions:
 An outfall node can have only one conduit link connected to it.
 A flow divider node must have exactly two outflow links.
 A node cannot have more than one dummy link connected to it.
 Under Kinematic Wave routing, a junction node can only have one outflow link and a
regulator link cannot be the outflow link of a non-storage node.
 Under Dynamic Wave routing there must be at least one outfall node in the network.
An error message will be generated if any of these conditions are violated. Excessive Continuity Errors When a run completes successfully, the mass continuity errors for runoff, flow routing, and
pollutant routing will be displayed in the Run Status window. These errors represent the percent
difference between initial storage + total inflow and final storage + total outflow for the entire
drainage system. If they exceed some reasonable level, such as 10 percent, then the validity of
the analysis results must be questioned. The most common reasons for an excessive continuity
error are computational time steps that are too long or conduits that are too short. In addition to the system continuity error, the Status Report produced by a run (see Section 9.1)
will list those nodes of the drainage network that have the largest flow continuity errors. If the
error for a node is excessive, then one should first consider if the node in question is of
importance to the purpose of the simulation. If it is, then further study is warranted to determine
how the error might be reduced. Unstable Flow Routing Results Due to the explicit nature of the numerical methods used for Dynamic Wave routing (and to a
lesser extent, Kinematic Wave routing), the flows in some links or water depths at some nodes
may fluctuate or oscillate significantly at certain periods of time as a result of numerical
instabilities in the solution method. SWMM does not automatically identify when such conditions
exist, so it is up to the user to verify the numerical stability of the model and to determine if the
simulation results are valid for the modeling objectives. Time series plots at key locations in the
network can help identify such situations as can a scatter plot between a link’s flow and the
corresponding water depth at its upstream node (see Section 9.5, Viewing Results with a Graph). Numerical instabilities can occur over short durations and may not be apparent when time series
are plotted with a long time interval. When detecting such instabilities, it is recommended that a
reporting time step of 1 minute or less be used, at least for an initial screening of results. The run’s Status Report lists the links having the five highest values of a Flow Instability Index
(FII). This index counts the number of times that the flow value in a link is higher (or lower) than
the flow in both the previous and subsequent time periods. The index is normalized with respect to the expected number of such ‘turns’ that would occur for a purely random series of values and
can range from 0 to 150. As an example of how the Flow Instability Index can be used, consider Figure 8-1 shown below.
The solid line plots the flow hydrograph for the link identified as having the highest FII value (100)
in a dynamic wave flow routing run that used a fixed time step of 30 seconds. The dashed line
shows the hydrograph that results when a variable time step was used instead, which is now
completely stable.
0
200
400
600
800
0 2 4 6 8 10 12
Time (hours)
Flow (cfs)
Fixed Time Step
(FII = 100)
Variable Time Step
(FII = 0)

FIGURE 8-1 FLOW INSTABILITY INDEX FOR A FLOW HYDROGRAPH

Flow time series plots for the links having the highest FII’s should be inspected to insure that flow
routing results are acceptably stable. Numerical instabilities under Dynamic Wave flow routing can be reduced by:
 reducing the routing time step
 utilizing the variable time step option with a smaller time step factor
 selecting to ignore the inertial terms of the momentum equation
 selecting the option to lengthen short conduits.

CHAPTER 9 – VIEWING RESULTS

This chapter describes the different ways in which the results of a simulation can be viewed.
These include a status report, a summary report, various map views, graphs, tables, and a
statistical frequency report.

9.1 Viewing a Status Report

A Status Report is available for viewing after each simulation. It contains:
 a summary of the main Simulation Options that are in effect
 a list of any error conditions encountered during the run
 a summary listing of the project’s input data (if requested in the Simulation Options)
 a summary of the data read from each rainfall file used in the simulation
 a description of each control rule action taken during the simulation (if requested in the
Simulation Options)
 the system-wide mass continuity errors for:
o runoff quantity and quality
o groundwater flow
o conveyance system flow and water quality
 the names of the nodes with the highest individual flow continuity errors
 the names of the conduits that most often determined the size of the time step used for
flow routing (only when the Variable Time Step option is used)
 the names of the links with the highest Flow Instability Index values
 information on the range of routing time steps taken and the percentage of these that
were considered steady state.
To view the Status Report select Report >> Status from the Main Menu or click the button
and select Status Report from the drop-down menu that appears. To copy selected text from the Status Report to a file or to the Windows Clipboard, first select the
text to copy with the mouse and then choose Edit >> Copy To from the Main Menu (or press the
button on the Standard Toolbar).
To save both the entire Status Report and Summary Report (discussed next) to file, select File
Export >> Status/Summary Report from the Main Menu.

9.2 Viewing Summary Results

SWMM’s Summary Results report lists summary results for each subcatchment, node, and link in
the project through a selectable list of tables. To view the various summary results tables, select Report >> Summary from the Main Menu or click the button and select Summary Results
from the drop-down menu that appears. The Summary Results window looks as follows: The drop-down box at the upper left allows you to choose the type of results to view. The
selection of tables and the results they display are as follows: Table Columns Subcatchment Runoff Total precipitation (in or mm);
Total run-on from other subcatchments (in or mm);
Total evaporation (in or mm);
Total infiltration (in or mm);
Total runoff depth (in or mm);
Total runoff volume (million gallons or million liters);
Peak runoff (flow units);
Runoff coefficient (ratio of total runoff to total precipitation). LID Performance Total inflow volume
Total evaporation loss
Total infiltration loss
Total surface outflow
Total underdrain outflow
Initial storage volume
Final storage volume
Flow continuity error (%)
Note: all quantities are expressed as depths (in or mm) over the LID
unit’s surface area. Groundwater Summary Total surface infiltration (in or mm)
Total evaporation (in or mm)
Total lower seepage (in or mm)
Total lateral outflow (in or mm)
Maximum lateral outflow (flow units)
Average upper zone moisture content (volume fraction)
Average water table elevation (ft or m)
Final upper zone moisture content (volume fraction)
Final water table elevation (ft or m) Subcatchment Washoff
Total mass of each pollutant washed off the subcatchment (lbs or
kg). Node Depth
Average water depth (ft or m);
Maximum water depth (ft or m);
Maximum hydraulic head (HGL) elevation (ft or m);
Time of maximum depth;
Maximum water depth at reporting times (ft or m). Node Inflow Maximum lateral inflow (flow units);
Maximum total inflow (flow units);
Time of maximum total inflow;
Total lateral inflow volume (million gallons or million liters);
Total inflow volume (million gallons or million liters);
Flow balance error (%).
Note: Total inflow consists of lateral inflow plus inflow from
connecting links. Node Surcharge Hours surcharged;
Maximum height of surcharge above node’s crown (ft or m);
Minimum depth of surcharge below node’s top rim (ft or m).
Note: surcharging occurs when water rises above the crown of the
highest conduit and only those conduits that surcharge are listed. Node Flooding Hours flooded;
Maximum flooding rate (flow units);
Time of maximum flooding;
Total flood volume (million gallons or million liters);
Peak depth (for dynamic wave routing in ft or m) or peak volume
(1000 ft^3 or 1000 m^3 ) of ponded surface water.
Note: flooding refers to all water that overflows a node, whether it
ponds or not, and only those nodes that flood are listed. Storage Volume Average volume of water in the facility ( 10 00 ft^3 or 1000 m^3 );
Average percent of full storage capacity utilized;
Percent of total stored volume lost to evaporation;
Percent of total stored volume lost to seepage;
Maximum volume of water in the facility ( 1000 ft^3 or 1000 m^3 );
Maximum percent of full storage capacity utilized;
Time of maximum water stored;
Maximum outflow rate from the facility (flow units). Outfall Loading Percent of time that outfall discharges;
Average discharge flow (flow units);
Maximum discharge flow (flow units);
Total volume of flow discharged (million gallons or million liters);
Total mass discharged of each pollutant (lbs or kg). Link Flow Maximum flow (flow units);
Time of maximum flow;
Maximum velocity (ft/sec or m/sec)
Ratio of maximum flow to full normal flow;
Ratio of maximum flow depth to full depth. Flow Classification Ratio of adjusted conduit length to actual length;
Fraction of all time steps spent in the following flow categories:
 dry on both ends
 dry on the upstream end
 dry on the downstream end
 subcritical flow
 supercritical flow
 critical flow at the upstream end
 critical flow at the downstream end
Fraction of all time steps flow is limited to normal flow;
Fraction of all time steps flow is inlet controlled (for culverts only). Conduit Surcharge Hours that conduit is full at:
 both ends
 upstream end
 downstream end
Hours that conduit flows above full normal flow;
Hours that conduit is capacity limited
Note: only conduits with one or more non-zero entries are listed and
a conduit is considered capacity limited if its upstream end is full and
the HGL slope is greater than the conduit slope.
Link Pollutant Loads Total mass load (in lbs or kg) of each pollutant carried by the link
over the entire simulation period. Pumping Percent of time that the pump is on line;
Number of pump start-ups;
Minimum flow pumped (flow units)
Average flow pumped (flow units)
Maximum flow pumped (flow units);
Total volume pumped (million gallons or million liters);
Total energy consumed assuming 100% efficiency (Kw-hrs);
Percent of time that the pump operates below its pump curve;
Percent of time that the pump operates above its pump curve.
The summary results displayed in these tables are based on results found at every
computational time step and not just on the results from each reporting time step.
Clicking on the name of an object in the first column of the table will locate that object both in the
Project Browser and on the Study Area Map. Clicking on a column heading will sort the entries in
the table by the values in that column (alternating between ascending and descending order with
each click. Selecting Edit >> Copy To from the Main Menu or clicking on the Standard Toolbar will allow
you to copy the contents of the table to either the Windows Clipboard or to a file. To save both the
entire Status Report and all tables of the Summary Report to a file select File >> Export >>
Status/Summary Report from the Main Menu.

9.3 Time Series Results

Computed results at each reporting time step for the variables listed in Table 9-1 are available for
viewing on the map and can be plotted, tabulated, and statistically analyzed. These variables can
be viewed only for those subcatchments, nodes, and links that were selected to have detailed
time series results saved for them. This normally includes all such objects in the project unless
the Reporting option (under the Options category in the Project Browser) was used to select
specific objects to report on.

TABLE 9-1 TIME SERIES VARIABLES AVAILABLE FOR VIEWING

Subcatchment Variables
Link Variables ▪ rainfall rate (in/hr or mm/hr) ▪ snow depth (in or mm) ▪ evaporation loss ( in/ day or mm/day) ▪ infiltration loss (in/hr or mm/hr) ▪ runoff flow (flow units) ▪ groundwater flow into the drainage network
(flow units) ▪ groundwater elevation (ft or m) ▪ soil moisture in the unsaturated groundwater
zone (volume fraction) ▪ washoff concentration of each pollutant
(mass/liter)
▪ flow rate (flow units)
▪ average water depth (ft or m)
▪ flow velocity (ft/sec or m/sec)
▪ volume of water (ft^3 or m^3 )
▪ capacity (fraction of full area filled by flow
for conduits; control setting for pumps and
regulators)
▪ concentration of each pollutant
(mass/liter)
Node Variables ▪ water depth (ft or m above the node invert
elevation) ▪ hydraulic head (ft or m, absolute elevation per
vertical datum) ▪ stored water volume (including ponded water,
ft^3 or m^3 )
▪ lateral inflow (runoff + all other external
inflows, in flow units) ▪ total inflow (lateral inflow + upstream inflows,
in flow units) ▪ surface flooding (excess overflow when the
node is at full depth, in flow units) ▪ concentration of each pollutant after any
treatment applied at the node (mass/liter)
System-Wide Variables
▪ air temperature (degrees F or C)
▪ potential evaporation (in/day or mm/day)
▪ actual evaporation (in/day or mm/day)
▪ total rainfall (in/hr or mm/hr)
▪ total snow depth (in or mm)
▪ average losses (in/hr or mm/hr)
▪ total runoff flow (flow units)
▪ total dry weather inflow (flow units)
▪ total groundwater inflow (flow units)
▪ total RDII inflow (flow units)
▪ total direct inflow (flow units)
▪ total external inflow (flow units)
▪ total external flooding (flow units)
▪ total outflow from outfalls (flow units)
▪ total nodal storage volume ( ft^3 or m^3 )

9.4 Viewing Results on the Map

There are several ways to view the values of certain input parameters and simulation results
directly on the Study Area Map:
 For the current settings on the Map Browser, the subcatchments, nodes and links of the
map will be colored according to their respective Map Legends. The map's color coding
will be updated as a new time period is selected in the Map Browser.
 When the Flyover Map Labeling program preference is selected (see Section 4.9),
moving the mouse over any map object will display its ID name and the value of its
current theme parameter in a hint-style box.
 ID names and parameter values can be displayed next to all subcatchments, nodes
and/or links by selecting the appropriate options on the Annotation page of the Map
Options dialog (see Section 7.12).
 Subcatchments, nodes or links meeting a specific criterion can be identified by submitting
a Map Query (see Section 7.9).
 You can animate the display of results on the network map either forward or backward in
time by using the controls on the Animator panel of the Map Browser (see Section 4.7).
 The map can be printed, copied to the Windows clipboard, or saved as a DXF file or
Windows metafile (see Section 7.13).

9.5 Viewing Results with a Graph…………………………………………………………………………….

Analysis results can be viewed using several different types of graphs. Graphs can be printed,
copied to the Windows clipboard, or saved to a text file or to a Windows metafile. The following
types of graphs can be created from available simulation results:
▪ Time Series Plot:
▪ Profile Plot:
▪ Scatter Plot:
You can zoom in or out of any graph by holding down the key while drawing a zoom
rectangle with the mouse’s left button held down. Drawing the rectangle from left to right zooms
in, drawing it from right to left zooms out. The plot can also be panned in any direction by moving
the mouse across the plot with the left button held down An opened graph will normally be redrawn when a new simulation is run. To prevent the
automatic updating of a graph once a new set of results is computed you can lock the current graph by clicking the icon in the upper left corner of the graph. To unlock the graph, click the
icon again. Time Series Plots A Time Series Plot graphs the values over time of specific combinations of objects and variables.
Up to six time series can be plotted on the same graph. When only a single time series is plotted,
and that item has calibration data registered for the plotted variable, then the calibration data will be plotted along with the simulated results (see Section 5.5 for instructions on how to register
calibration data with a project). To create a Time Series Plot:
  1. Select Report >> Graph >> Time Series from the Main Menu or click on the
    Standard Toolbar.
  2. A Time Series Plot Selection dialog will appear. Use it to describe what objects and
    quantities should be plotted.
The Time Series Plot Selection dialog specifies a set of objects and their variables whose
computed time series will be graphed in a Time Series Plot. The dialog is used as follows:
  1. Select a Start Date and End Date for the plot (the default is the entire simulation period).
  2. Choose whether to show time as Elapsed Time or as Date/Time values.
  3. Add up to six different data series to the plot by clicking the Add button above the data
    series list box.
  4. Use the Edit button to make changes to a selected data series or the Delete button to
    delete a data series.
  5. Use the Up and Down buttons to change the order in which the data series will be
    plotted.
  6. Click the OK button to create the plot.
When you click the Add or Edit buttons a Data Series Selection dialog will be displayed for
selecting a particular object and variable to plot. It contains the following data fields: Object Type: The type of object to plot (Subcatchment, Node, Link or System). Object Name: The ID name of the object to be plotted. (This field is disabled for System
variables). Variable: The variable whose time series will be plotted (choices vary by object type). Legend Label: The text to use in the legend for the data series. If left blank, a default label
made up of the object type, name, variable and units will be used (e.g. Link
C16 Flow (CFS)). Axis: Whether to use the left or right vertical axis to plot the data series.
As you select objects on the Study Area Map or in the Project Browser their types and ID
names will automatically appear in this dialog.
Click the Accept b utton to add/update the data series into the plot or click the Cancel button to
disregard your edits. You will then be returned to the Time Series Plot Selection dialog where you
can add or edit another data series.
To make a precipitation time series display in inverted fashion on a plot, assign it to the
right axis and after the plot is displayed, use the Graph Options Dialog (see Section 9.6)
to invert the right axis and expand the scales of both the left and right axes (so it doesn't
overlap another data series).
Profile Plots A Profile Plot displays the variation in simulated water depth with distance over a connected path
of drainage system links and nodes at a particular point in time. Once the plot has been created it
will be automatically updated as a new time period is selected using the Map Browser. To create a Profile Plot:
  1. Select Report >> Graph >> Profile from the main menu or press on the Standard
    Toolbar
  2. A Profile Plot Selection dialog will appear (see below). Use it to identify the path along
    which the profile plot is to be drawn.
The Profile Plot Selection dialog is used to specify a path of connected conveyance system links
along which a water depth profile versus distance should be drawn. To define a path using the
dialog:
  1. Enter the ID of the upstream node of the first link in the path in the Start Node edit field
(or click on the node on the Study Area Map and then on the button next to the edit
field).
  1. Enter the ID of the downstream node of the last link in the path in the End Node edit field
(or click the node on the map and then click the button next to the edit field).
  1. Click the Find Path button to have the program automatically identify the path with the
    smallest number of links between the start and end nodes. These will be listed in the
    Links in Profile box.
  2. You can insert a new link into the Links in Profile list by selecting the new link either on
the Study Area Map or in the Project Browser and then clicking the button
underneath the Links in Profile list box.
  1. Entries in the Links in Profile list can be deleted or rearranged by using the , ,
and buttons underneath the list box.
  1. Click the OK button to view the profile plot.
To save the current set of links listed in the dialog for future use:
  1. Click the Save Current Profile button.
  2. Supply a name for the profile when prompted.
To use a previously saved profile:
  1. Click the Use Saved Profile button.
  2. Select the profile to use from the Profile Selection dialog that appears.
Profile plots can also be created before any simulation results are available, to help visualize and
verify the vertical layout of a drainage system. Plots created in this manner will contain a refresh button in the upper left corner that can be used to redraw the plot after edits are made to any
elevation data appearing in the plot. Scatter Plots A Scatter Plot displays the relationship between a pair of variables, such as flow rate in a pipe
versus water depth at a node. To create a Scatter Plot:
  1. Select Report >> Graph >> Scatter from the main menu or press on the Standard
    Toolbar
  2. Specify what time interval and what pair of objects and their variables to plot using the
    Scatter Plot Selection dialog that appears.
The Scatter Plot Selection dialog is used to select the objects and variables to be graphed
against one another in a scatter plot. Use the dialog as follows:
  1. Select a Start Date and End Date for the plot (the default is the entire simulation period).
  2. Select the following choices for the X-variable (the quantity plotted along the horizontal
    axis):
    a. Object Category (Subcatchment, Node or Link)
    b. Object ID (enter a value or click on the object either on the Study Area Map or in
the Project Browser and then click the button on the dialog)
c. Variable to plot (choices depend on the category of object selected).
  1. Do the same for the Y-variable (the quantity plotted along the vertical axis).
  2. Click the OK button to create the plot.

9.6 Customizing a Graph’s Appearance

To customize the appearance of a graph:
  1. Make the graph the active window (click on its title bar).
  2. Select Report >> Customize from the Main Menu, or click on the Standard Toolbar,
    or right-click on the graph.
  3. Use the Graph Options dialog that appears to customize the appearance of a Time
    Series or Scatter Plot, or use the Profile Plot Options dialog for a Profile Plot.
Graph Options Dialog The Graph Options dialog is used to customize the appearance of a time series plot, a scatter
plot, or a frequency plot (described in Section9.8). To use the dialog:
  1. Select from among the four tabbed pages that cover the following categories of options:
    General, Axes , Legend, and Styles.
  2. Check the Default box if you wish to use the current settings as defaults for all new
    graphs as well.
  3. Select OK to accept your selections.
Graph Options – General The following options can be set on the General page of the Graph Options dialog box:
Panel Color Color of the panel that contains the graph
Start Background
Color
Starting gradient color of graph's plotting area
End Background Ending gradient color of graph’s plotting area
Color
View in 3D Check if graph should be drawn in 3D
3D Effect Percent Degree to which 3D effect is drawn
Main Title Text of graph's main title
Font Click to set the font used for the main title
The figure below shows a 3D graph with White as the Start Background Color and Sky Blue as
the End Background Color. Graph Options – Axes The Axes page of the Graph Options dialog box adjust the way that the axes are drawn on a
graph. One first selects an axis (Bottom, Left or Right (if present)) to work with and then selects
from the following options:
Gridlines Displays grid lines on the graph.
Inverted Inverts the scale of the right vertical axis.
Auto Scale (^) Fills in the Minimum, Maximum and Increment boxes with an
automatic axis scaling.
Minimum Sets the minimum axis value (the minimum data value is shown
in parentheses). Can be left blank.
Maximum Sets the maximum axis value (the maximum data value is
shown in parentheses). Can be left blank.
Increment Sets increment between axis labels. Can be left blank or set to
zero for the program to automatically select an increment.
Axis Title Text of axis title.
Font Click to select a font for the axis title.
Graph Options – Legend The Legend page of the Graph Options dialog box controls how the legend is displayed on the
graph.
Position Selects where to place the legend.
Color Selects color to use for legend background.
Check Boxes If selected, check boxes will appear next to each legend entry,
allowing one to make the data series visible or invisible on the
graph.
Framed Places a frame around the legend.
Shadowed (^) Places a shadow behind the legend’s text.
Transparent Makes the legend background transparent.
Visible Makes the legend visible.
Symbol Width Selects the width used to draw the symbol portion of a legend
item, as a percentage of the length of the longest legend label.
Graph Options – Styles
The Styles page of the Graph Options dialog box controls how individual data series (or curves)
are displayed on a graph. To use this page:
  1. Select a data series to work with from the Series combo box.
  2. Edit the title used to identify this series in the legend.
  3. Click the Font button to change the font used for the legend. (Other legend properties are
    selected on the Legend page of the dialog.)
  4. Select a property of the data series you would like to modify (not all properties are
    available for some types of graphs). The choices are:
     Lines
     Markers
     Patterns
     Labels
Profile Plot Options Dialog The Profile Plot Options dialog is used to customize the appearance of a Profile Plot. The dialog
contains four pages:
Colors:
 Selects the color to use for the plot window panel, the plot background, a conduit’s
interior, and the depth of filled water.
 Includes a "Display Conduits Only" check box that provides a closer look at the water
levels within conduits by removing all other details from the plot.
Axes:
 Edit s the main and axis titles, including their fonts.
 Selects to display horizontal and vertical axis grid lines.
Node Labels:
 Selects to display node ID labels either along the plot’s top axis, directly on the plot
above the node’s crown height, or both.
 Selects the length of arrow to draw between the node label and the node’s crown on
the plot (use 0 for no arrows).
 Selects the font size of the node ID labels.
Vertical Scale:
 Lets one choose the minimum, maximum, and increment values for the vertical axis
scale, or have SWMM set the scale automatically. If the increment field contains 0 or
is left blank the program will automatically select an increment to use.
Check the Default box if you want these options (except the Vertical Scale) to apply to all new
profile plots when they are first created.

9.7 Viewing Results with a Table

Time series results for selected variables and objects can also be viewed in a tabular format.
There are two types of formats available:
 Table by Object - tabulates the time series of several variables for a single object (e.g.,
flow and water depth for a conduit).
 Table by Variable - tabulates the time series of a single variable for several objects of the
same type (e.g., runoff for a group of subcatchments).
To create a tabular report:
  1. Select Report >> Table from the Main Menu or click o n the Standard Toolbar.
  2. Choose the table format (either By Object or By Variable) from the sub-menu that
    appears.
  3. Fill in the Table by Object or Table by Variable dialogs to specify what information the
    table should contain.
The Table by Object dialog is used when creating a time series table of several variables for a
single object. Use the dialog as follows: Select a Start Date and End Date for the table (the default is the entire simulation period).
  1. Choose whether to show time as Elapsed Time or as Date/Time values.
  2. Choose an Object Category (Subcatchment, Node, Link, or System).
  3. Identify a specific object in the category by clicking the object either on the Study Area
Map or in the Project Browser and then clicking the button on the dialog. Only a
single object can be selected for this type of table.
  1. Check off the variables to be tabulated for the selected object. The available choices
    depend on the category of object selected.
  2. Click the OK button to create the table.
The Table by Variable dialog is used when creating a time series table of a single variable for one
or more objects. Use the dialog as follows:
  1. Select a Start Date and End Date for the table (the default is the entire simulation period).
  2. Choose whether to show time as Elapsed Time or as Date/Time values.
  3. Choose an Object Category (Subcatchment, Node or Link).
  4. Select a simulated variable to be tabulated. The available choices depend on the
    category of object selected.
  5. Identify one or more objects in the category by successively clicking the object either on
the Study Area Map or in the Project Browser and then clicking the button on the
dialog.
  1. Click the OK button to create the table.
Objects already selected can be deleted, moved up in the order or moved down in the order by clicking the , , and buttons, respectively.

9.8 Viewing a Statistics Report vii

A Statistics Report can be generated from the time series of simulation results. For a given object
and variable this report will do the following:
 segregate the simulation period into a sequence of non-overlapping events, either by
day, month, or by flow (or volume) above some minimum threshold value,
 compute a statistical value that characterizes each event, such as the mean, maximum,
or total sum of the variable over the event's time period,
 compute summary statistics for the entire set of event values (mean, standard deviation
and skewness),
 perform a frequency analysis on the set of event values.
The frequency analysis of event values will determine the frequency at which a particular event
value has occurred and will also estimate a return period for each event value. Statistical
analyses of this nature are most suitable for long-term continuous simulation runs. To generate a Statistics Report:
  1. Select Report >> Statistics from the Main Menu or click on the Standard Toolbar.
  2. Fill in the Statistics Report Selection dialog that appears, specifying the object, variable,
    and event definition to be analyzed.
Object Category Select the category of object to analyze (Subcatchment, Node, Link or System). Object Name Enter the ID name of the object to analyze. Instead of typing in an ID name, you can select the object on the Study Area Map or in the Project Browser and then click the button to select it
into the Object Name field. Variable Analyzed Select the variable to be analyzed. The available choices depend on the object category selected
(e.g., rainfall, losses, or runoff for subcatchments; depth, inflow, or flooding for nodes; depth, flow,
velocity, or capacity for links; water quality for all categories). Event Time Period Select the length of the time period that defines an event. The choices are daily, monthly, or
event-dependent. In the latter case, the event period depends on the number of consecutive
reporting periods where simulation results are above the threshold values defined below. Statistic Choose an event statistic to be analyzed. The available choices depend on the choice of variable
to be analyzed and include such quantities as mean value, peak value, event total, event
duration, and inter-event time (i.e., the time interval between the midpoints of successive events).
For water quality variables the choices include mean concentration, peak concentration, mean
loading, peak loading, and event total load. Event Thresholds These define minimum values that must be exceeded for an event to occur:
 The Analysis Variable threshold specifies the minimum value of the variable being
analyzed that must be exceeded for a time period to be included in an event.
 The Event Volume threshold specifies a minimum flow volume (or rainfall volume) that
must be exceeded for a result to be counted as part of an event.
 Separation Time sets the minimum number of hours that must occur between the end of
one event and the start of the next event. Events with fewer hours are combined
together. This value applies only to event-dependent time periods (not to daily or monthly
event periods).
If a particular type of threshold does not apply, then leave the field blank. After the choices made on the Statistics Selection dialog form are processed, a Statistics Report
is produced as shown below. It consists of four tabbed pages that contain:
 a table of event summary statistics
 a table of rank-ordered event periods, including their date, duration, and magnitude
 a histogram plot of the chosen event statistic
 an exceedance frequency plot of the event values.
The exceedance frequencies included in the Statistics Report are computed with respect to the
number of events that occur, not the total number of reporting periods.

CHAPTER 10 – PRINTING AND COPYING

This chapter describes how to print, copy to the Windows clipboard, or copy to file the contents of
the currently active window in the SWMM workspace. This can include the study area map, a
graph, a table, or a report.

10.1 Selecting a Printer

To select a printer from among your installed Windows printers and set its properties:
  1. Select File >> Page Setup from the Main Menu.
  2. Click the Printer button on the Page Setup dialog that appears (see below).
  3. Select a printer from the choices available in the combo box in the Print Setup dialog that
    appears.
  4. Click the Properties button to select the appropriate printer properties (which vary with
    choice of printer).
  5. Click OK on each dialog to accept your selections.

10.2 Setting the Page Format

To format the printed page:
  1. Select File >> Page Setup from the main menu.
  2. Use the Margins page of the Page Setup dialog form that appears (see above) to:
    • Select a printer.
    • Select the paper orientation (Portrait or Landscape).
    • Set left, right, top, and bottom margins.
  3. Use the Headers/Footers page of the dialog box (see below) to:
    • Supply the text for a header that will appear on each page.
    • Indicate whether the header should be printed or not and how its text should be
      aligned.
    • Supply the text for a footer that will appear on each page.
    • Indicate whether the footer should be printed or not and how its text should be
      aligned.
    • Indicate whether pages should be numbered.
  4. Click OK to accept your choices.

10.3 Print Preview…………………………………………………………………………………………………….

To preview a printout select File >> Print Preview from the Main Menu. A Preview form will
appear which shows how each page being printed will appear. While in preview mode, the left
mouse button will re-center and zoom in on the image and the right mouse button will re-center
and zoom out.

10.4 Printing the Current View

To print the contents of the current window being viewed in the SWMM workspace, either select File >> Print from the Main Menu or click on the Standard Toolbar. The following views can
be printed:
 Study Area Map (at the current zoom level)
 Status Report.
 Summary report (for the current table being viewed)
 Graphs (Time Series, Profile, and Scatter plots)
 Tabular Reports
 Statistical Reports.

10.5 Copying to the Clipboard or to a File

SWMM can copy the text and graphics of the current window being viewed to the Windows
clipboard or to a file. Views that can be copied in this fashion include the Study Area Map,
summary report tables, graphs, time series tables, and statistical reports. To copy the current
view to the clipboard or to file:
  1. If the current view is a time series table, select the cells of the table to copy by dragging
    the mouse over them or copy the entire table by selecting Edit >> Select All from the
    Main Menu.
  2. Select Edit >> Copy To from the Main Menu or click the button on the Standard
    Toolbar.
  3. Select choices from the Copy dialog that appears (see below) and click the OK button.
  4. If copying to file, enter the name of the file in the Save As dialog that appears and click
    OK.
Use the Copy dialog as follows to define how you want your data copied and to where:
  1. Select a destination for the material being copied (Clipboard or File)
  2. Select a format to copy in:
     Bitmap (graphics only)
     Metafile (graphics only)
     Data (text, selected cells in a table, or data used to construct a graph)
  3. Click OK to accept your selections or Cancel to cancel the copy request.
The bitmap format copies the individual pixels of a graphic. The metafile format copies the
instructions used to create the graphic and is more suitable for pasting into word processing
documents where the graphic can be re-scaled without losing resolution. When data is copied, it
can be pasted directly into a spreadsheet program to create customized tables or charts.

CHAPTER 11 – FILES USED BY SWMM

This section describes the various files that SWMM can utilize. They include: the project file, the
report and output files, rainfall files, the climate file, calibration data files, time series files, and
interface files. The only file required to run SWMM is the project file; the others are optional.

11.1 Project Files

A SWMM project file is a plain text file that contains all of the data used to describe a study area
and the options used to analyze it. The file is organized into sections, where each section
generally corresponds to a particular category of object used by SWMM. The contents of the file
can be viewed from within SWMM while it is open by selecting Project >> Details from the Main
Menu. An existing project file can be opened by selecting File >> Open from the Main Menu and
be saved by selecting File >> Save (or File >> Save As). Normally a SWMM user would not edit the project file directly, since SWMM’s graphical user
interface can add, delete, or modify a project’s data and control settings. However, for large
projects where data currently reside in other electronic formats, such as CAD or GIS files, it may
be more expeditious to extract data from these sources and save it to a formatted project file
before running SWMM. The format of the project file is described in detail in Appendix D of this
manual. After a project file is saved to disk, a settings file will automatically be saved with it. This file has
the same name as the project file except that its extension is .ini (e.g., if the project file were
named project1.inp then its settings file would have the name project1.ini). It contains various
settings used by SWMM’s graphical user interface, such as map display options, legend colors
and intervals, object default values, and calibration file information. Users should not edit this file.
A SWMM project will still load and run even if the settings file is missing.

11.2 Report and Output Files

The report file is a plain text file created after every SWMM run that contains the contents of both
the Status Report and all of the tables included in the Summary Results report. Refer to
Sections 9.1 and 9.2 to review their contents. The output file is a binary file that contains the numerical results from a successful SWMM run.
This file is used by SWMM’s user interface to interactively create time series plots and tables,
profile plots, and statistical analyses of a simulation’s results. Whenever a successfully run project is either saved or closed, the report and output files are
saved with the same name as the project file, but with extensions of .rpt and .out. This will
happen automatically if the program preference Prompt to Save Results is turned off (see Section
4.9). Otherwise the user is asked if the current results should be saved or not. If results are saved then the next time the project is opened, the results from these files will automatically be available
for viewing.

11.3 Rainfall Files

SWMM’s rain gage objects can utilize rainfall data stored in external rainfall files. The program
currently recognizes the following formats for storing such data:
 Hourly and fifteen minute precipitation data from over 5,500 reporting stations retrieved
using NOAA’s National Climatic Data Center (NCDC) Climate Data Online service
(www.ncdc.noaa.gov/cdo-web) (space-delimited text format only).
 The older DS-3240 and related formats used for hourly precipitation by NCDC.
 The older DS-3260 and related formats used for fifteen minute precipitation by NCDC.
 HLY03 and HLY21 formats for hourly rainfall at Canadian stations, available from
Environment Canada at http://www.climate.weather.gc.ca.
 FIF21 format for fifteen minute rainfall at Canadian stations, also available online from
Environment Canada.
 a standard user-prepared format where each line of the file contains the station ID, year,
month, day, hour, minute, and non-zero precipitation reading, all separated by one or
more spaces.
When requesting data from NCDC’s online service, be sure to specify the TEXT format option,
make sure that the data flags are included, and, for 15-minute data, select the QPCP option and
not the QGAG one. An excerpt from a sample user-prepared Rainfall file is as follows:
STA01 2004 6 12 00 00 0.12
STA01 2004 6 12 01 00 0.04
STA01 2004 6 22 16 00 0.07
This format can also accept multiple stations within the same file. When a rain gage is designated as receiving its rainfall data from a file, the user must supply the
name of the file and the name of the recording station referenced in the file. For the standard
user-prepared format, the rainfall type (e.g., intensity or volume), recording time interval, and
depth units must also be supplied as rain gage properties. For the other file types these
properties are defined by their respective file format and are automatically recognized by SWMM.

11.4 Climate Files

SW MM can use an external climate file that contains daily air temperature, evaporation, and wind
speed data. The program currently recognizes the following formats:
 Global Historical Climatology Network - Daily (GHCN-D) files (TEXT output format)
available from NOAA's National Climatic Data Center (NCDC) Climate Data Online
service at http://www.ncdc.noaa.gov/cdo-web.
 Older NCDC DS-3200 or DS-3210 files.
 Canadian climate files available from Environment Canada at
http://www.climate.weather.gc.ca.
 A user-prepared climate file where each line contains a recording station name, the year,
month, day, maximum temperature, minimum temperature, and optionally, evaporation
rate, and wind speed. If no data are available for any of these items on a given date, then
an asterisk should be entered as its value.
When a climate file has days with missing values, SWMM will use the value from the most recent
previous day with a recorded value.
For a user-prepared climate file, the data must be in the same units as the project being
analyzed. For US units, temperature is in degrees F, evaporation is in inches/day, and
wind speed is in miles/hour. For metric units, temperature is in degrees C, evaporation is
in mm/day, and wind speed is in km/hour.

11.5 Calibration Files

Calibration files contain measurements of variables at one or more locations that can be
compared with simulated values in Time Series Plots. Separate files can be used for each of the
following:
 Subcatchment Runoff
 Subcatchment Groundwater Flow
 Subcatchment Groundwater Elevation
 Subcatchment Snow Pack Depth
 Subcatchment Pollutant Washoff
 Node Depth
 Node Lateral Inflow
 Node Flooding
 Node Water Quality
 Link Flow
 Link Velocity
 Link Depth
Calibration files are registered to a project by selecting Project >> Calibration Data from the
main menu (see Section 5.7). The format of the file is as follows:
  1. The name of the first object with calibration data is entered on a single line.
  2. Subsequent lines contain the following recorded measurements for the object:
     measurement date (month/day/year, e.g., 6/21/2004) or number of whole days
    since the start of the simulation
     measurement time (hours:minutes) on the measurement date or relative to the
    number of elapsed days
     measurement value (for pollutants, a value is required for each pollutant).
  3. Follow the same sequence for any additional objects.
An excerpt from an example calibration file is shown below. It contains flow values for two
conduits: 1030 and 1602. Note that a semicolon can be used to begin a comment. I n this
example, elapsed time rather than the actual measurement date was used. ;Flows for Selected Conduits
;Conduit Days Time Flow
;—————————–
1030
0 0:15 0
0 0:30 0
0 0:45 23.88
0 1:00 94.58
0 1:15 115.37
1602
0 0:15 5.76
0 0:30 38.51
0 1:00 67.93
0 1:15 68.01

11.6 Time Series Files

Time series files are external text files that contain data for SWMM’s time series objects.
Examples of time series data include rainfall, evaporation, inflows to nodes of the drainage
system, and water stage at outfall boundary nodes. The file must be created and edited outside of
SWMM, using a text editor or spreadsheet program. A time series file can be linked to a specific
time series object using SWMM’s Time Series Editor (see Section C.19). The format of a time series file consists of one time series value per line. Comment lines can be
inserted anywhere in the file as long as they begin with a semicolon. Time series values can
either be in date / time / value format or in time / value format, where each entry is separated by
one or more spaces or tab characters. For the date / time / value format, dates are entered as month/day/year (e.g., 7/21/2004) and times as 24-hour military time (e.g., 8:30 pm is 20:30). After
the first date, additional dates need only be entered whenever a new day occurs. For the time /
value format, time can either be decimal hours or military time since the start of a simulation (e.g.,
2 days, 4 hours and 20 minutes can be entered as either 52.333 or 52:20). An example of a time
series file is shown below: ;Rainfall Data for Gage G1
07/01/2003 00:00 0.00000
00:15 0.03200
00:30 0.04800
00:45 0.02400
01:00 0.0100
07/06/2003 14:30 0.05100
14:45 0.04800
15:00 0.03000
18:15 0.01000
18:30 0.00800
In earlier releases of SWMM 5, a time series file was required to have two header lines of
descriptive text at the start of the file that did not have to begin with the semicolon
comment character. These files can still be used as long as they are modified by inserting
a semicolon at the front of the first two lines.
When preparing rainfall time series files, it is only necessary to enter periods with non-
zero rainfall amounts. SWMM interprets the rainfall value as a constant value lasting over
the recording interval specified for the rain gage which utilizes the time series. For all
other types of time series, SWMM uses interpolation to estimate values at times that fall
in between the recorded values.

11.7 Interface Files

SWMM can use several different kinds of interface files that contain either externally imposed
inputs (e.g., rainfall or infiltration/inflow hydrographs) or the results of previously run analyses
(e.g., runoff or routing results). These files can help speed up simulations, simplify comparisons
of different loading scenarios, and allow large study areas to be broken up into smaller areas that
can be analyzed individually. The different types of interface files that are currently available
include:
 rainfall interface file
 runoff interface file
 hot start file
 RDII interface file
 routing interface files
Consult Section 8.1, Setting Simulation Options, for instructions on how to specify interface files
for use as input and/or output in a simulation. Rainfall and Runoff Files The rainfall and runoff interface files are binary files created internally by SWMM that can be
saved and reused from one analysis to the next. The rainfall interface file collates a series of separate rain gage files into a single rainfall data file.
Normally a temporary file of this type is created for every SWMM analysis that uses external
rainfall data files and is then deleted after the analysis is completed. However, if the same rainfall
data are being used with many different analyses, requesting SWMM to save the rainfall interface
file after the first run and then reusing this file in subsequent runs can save computation time.
The rainfall interface file should not be confused with a rainfall data file. The latter is an
external text file that provides rainfall time series data for a single rain gage. The former
is a binary file created internally by SWMM that processes all of the rainfall data files
used by a project.
The runoff interface file can be used to save the runoff results generated from a simulation run. If
runoff is not affected in future runs, the user can request that SWMM use this interface file to
supply runoff results without having to repeat the runoff calculations again. Hot S tart Files Hot start files are binary files created by SWMM that contain the full hydrologic, hydraulic and
water quality state of the study area at the end of a run. The following information is saved to the
file:
 the ponded depth and its water quality for each subcatchment
 the pollutant mass buildup on each subcatchment
 the infiltration state of each subcatchment
 the conditions of any snowpack on each subcatchment
 the unsaturated zone moisture content, water table elevation, and groundwater outflow
for each subcatchment that has a groundwater zone defined for it
 the water depth, lateral inflow, and water quality at each node of the system
 the flow rate, water depth, control setting and water quality in each link of the system.
The hydrologic state of any LID units is not saved. The hot start file saved after a run can be used
to define the initial conditions for a subsequent run. Hot start files can be used to avoid the initial numerical instabilities that sometimes occur under
Dynamic Wave routing. For this purpose they are typically generated by imposing a constant set
of base flows (for a natural channel network) or set of dry weather sanitary flows (for a sewer network) over some startup period of time. The resulting hot start file from this run is then used to
initialize a subsequent run where the inflows of real interest are imposed. It is also possible to both use and save a hot start file in a single run, starting off the run with one
file and saving the ending results to another. The resulting file can then serve as the initial
conditions for a subsequent run if need be. This technique can be used to divide up extremely
long continuous simulations into more manageable pieces. Instructions to save and/or use a hot start file can be issued when editing the Interface Files
options available in the Project Browser (see Section8.1, Setting Simulation Options). One can
also use the File >> Export >> Hot Start File Main Menu command to save the results of a
current run at any particular time period to a hot start file. However, in this case only the results
for nodes, links and groundwater elevation will be saved. RDII Files The RDII i nterface file contains a time series of rainfall-dependent infiltration/inflow flows for a
specified set of drainage system nodes. This file can be generated from a previous SWMM run
when Unit Hydrographs and nodal RDII inflow data have been defined for the project, or it can be
created outside of SWMM using some other source of RDII data (e.g., through measurements or
output from a different computer program). RDII files generated by SWMM are saved in a binary
format. RDII files created outside of SWMM are text files with the same format used for r outing
interface files discussed below, where Flow is the only variable contained in the file. Routing Files A routing interface file stores a time series of flows and pollutant concentrations that are
discharged from the outfall nodes of drainage system model. This file can serve as the source of
inflow to another drainage system model that is connected at the outfalls of the first system. A
Combine utility is available on the File menu that will combine pairs of routing interface files into a
single interface file. This allows very large systems to be broken into smaller sub-systems that
can be analyzed separately and linked together through the routing interface file. Figure 11.1
below illustrates this concept. A single SWMM run can utilize an outflows routing file to save results generated at a system’s
outfalls, an inflows routing file to supply hydrograph and pollutograph inflows at selected nodes,
or both.
proj1.inp
save out1.dat
proj2.inp
save out2.dat
Combine
out1.dat + out2.dat >> inp3.dat
proj3.inp
use inp3.dat

FIGURE 11-1 COMBINING ROUTING INTERFACE FILES

RDII / Routing File Format RDII interface files and routing interface files have the same text format:
  1. the first line contains the keyword “SWMM5” (without the quotes)
  2. a line of text that describes the file (can be blank)
  3. the time step used for all inflow records (integer seconds)
  4. the number of variables stored in the file, where the first variable must always be flow
    rate
  5. the name and units of each variable (one per line), where flow rate is the first variable
    listed and is always named FLOW
  6. the number of nodes with recorded inflow data
  7. the name of each node (one per line)
  8. a line of text that provides column headings for the data to follow (can be blank)
  9. for each node at each time step, a line with:
     the name of the node
     the date (year, month, and day separated by spaces)
     the time of day (hours, minutes, and seconds separated by spaces)
     the flow rate followed by the concentration of each quality constituent
Time periods with no values at any node can be skipped. An excerpt from an RDII / routing
interface file is shown below.

SWMM5

Example File
300
1
FLOW CFS
2
N1
N2
Node Year Mon Day Hr Min Sec Flow
N1 2002 04 01 00 20 00 0.000000
N2 2002 04 01 00 20 00 0.002549
N1 2002 04 01 00 25 00 0.000000
N2 2002 04 01 00 25 00 0.002549

CHAPTER 12 – USING ADD-IN TOOLS

SWMM 5 has the ability to launch external applications from its graphical user interface that can
extend its capabilities. This section describes how such tools can be registered and share data
with SWMM 5.

12.1 What Are Add-In Tools

Add-in tools are third party applications that users can add to the Tools menu of the main SW MM
menu bar and be launched while SWMM is still running. SWMM can interact with these
applications to a limited degree by exchanging data through its pre-defined files (see Chapter 11)
or through the Windows clipboard. Add-in tools can provide additional modeling capabilities to
what SWMM already offers. Some examples of useful add-ins might include:
 a tool that performs a statistical analysis of long-term rainfall data prior to adding it to a
SWMM rain gage,
 an external spreadsheet program that would facilitate the editing of a SWMM data set,
 a unit hydrograph estimator program that would derive the R-T-K parameters for a set of
RDII unit hydrographs which could then be copied and pasted directly into SWMM’s Unit
Hydrograph Editor,
 a post-processor program that uses SWMM’s hydraulic results to compute suspended
solids removal through a storage unit,
 a third-party dynamic flow routing program used as a substitute for SWMM’s own internal
procedure.
The screenshot below shows what the Tools menu might look like after several add-in tools have
been registered with it. The Configure Tools option is used to add, delete, or modify add-in tools.
The options below this are the individual tools that have been made available (by this particular
user) and can be launched by selecting them from the menu.

12.2 Configuring Add-In Tools

To configure one’s personal collection of add-in tools, select Configure Tools from the Tools
menu. This will bring up the Tool Options dialog as shown below. The dialog lists the currently
available tools and has command buttons for adding a new tool and for deleting or editing an
existing tool. The up and down arrow buttons are used to change the order in which the
registered tools are listed on the Tools menu. Whenever the Add or Edit button is clicked on this dialog a Tool Properties dialog will appear.
This dialog is used to describe the properties of the new tool being added or the existing tool
being edited. The data entry fields of the Tool Properties dialog consist of the following: Tool Name This is the name to be used for the tool when it i s displayed in the Tools Menu. Program Enter the full path name to the program that will be launched when the tool is selected. You can click the button to bring up a standard Windows file selection dialog from which you can
search for the tool’s executable file name. Working Directory This field contains the name of the directory that will be used as the working directory when the tool is launched. You can click the button to bring up a standard directory selection dialog
from which you can search for the desired directory. You can also enter the macro symbol
$PROJDIR to utilize the current SWMM project’s directory or $SWMMDIR to use the directory
where the SWMM 5 executable resides. Either of these macros can also be inserted into the
Working Directory field by selecting its name in the list of macros provided on the dialog and then clicking the button. This field can be left blank, in which case the system’s current directory
will be used. Parameters This field contains the list of command line arguments that the tool’s executable program expects
to see when it is launched. Multiple parameters can be entered as long as they are separated by
spaces. A number of special macro symbols have been pre-defined, as listed in the Macros list
box of the dialog, to simplify the process of listing the command line parameters. When one of
these macro symbols is inserted into the list of parameters, it will be expanded to its true value
when the tool is launched. A specific macro symbol can either be typed into the Parameters field
or be selected from the Macros list (by clicking on it) and then added to the parameter list by clicking the button. The available macro symbols and their meanings are: $PROJDIR The directory where the current SWMM project file resides. $SWMMDIR The directory where the SWMM 5 executable is installed. $INPFILE The name of a temporary file containing the current project’s data that is
created just before the tool is launched. $RPTFILE The name of a temporary file that is created just before the tool is
launched and can be displayed after the tool closes by using the Report
Status command from the main SWMM menu.
$OUTFILE The name of a temporary file to which the tool can write simulation results
in the same format used by SWMM 5, which can then be displayed after
the tool closes in the same fashion as if a SWMM run were made. $RIFFILE The name of the Runoff Interface File, as specified in the Interface Files
page of the Simulation Options dialog, to which runoff simulation results
were saved from a previous SWMM run (see Sections 8.1 Setting
Simulation Options and 11.7 Interface Files). As an example of how the macro expansion works, consider the entries in the Tool Properties
dialog shown previously. This Spreadsheet Editor tool wants to launch Microsoft Excel and pass it
the name of the SWMM input data file to be opened by Excel. SWMM will issue the following
command line to do this C:\ Program Files (x86)\Microsoft Office\Office12\EXCEL.EXE $INPFILE where the string $INPFILE will be replaced by the name of the temporary file that SWMM
creates internally that contains the current project’s data. Disable SWMM while executing Check this option if SWMM should be hidden and disabled while the tool is executing. Normally
you will need to employ this option if the tool produces a modified input file or output file, such as
when the $INPFILE or $OUTFILE macros are used as command line parameters. When this
option is enabled, SWMM’s main window will be hidden from view until the tool is terminated. Update SWMM after closing Check this option if SWMM should be updated after the tool finishes executing. This option can
only be selected if the option to disable SWMM while the tool is executing was first selected.
Updating can occur in two ways. If the $INPFILE macro was used as a command line parameter
for the tool and the corresponding temporary input file produced by SWMM was updated by the
tool, then the current project’s data will be replaced with the data contained in the updated
temporary input file. If the $OUTFILE macro was used as a command line parameter, and its
corresponding file is found to contain a valid set of output results after the tool closes, then the
contents of this file will be used to display simulation results within the SWMM workspace. Generally speaking, the suppliers of third-party tools will provide instructions on what settings
should be used in the Tool Properties dialog to properly register their tool with SWMM.

APPENDIX A – USEFUL TABLES

A.1 Units of Measurement

PARAMETER US CUSTOMARY SI METRIC

Area (Subcatchment) acres hectares
Area (Storage Unit) square feet square meters
Area (Ponding) square feet square meters
Capillary Suction inches millimeters
Concentration mg/L (milligrams/liter)
ug/L (micrograms/liter)
Count/L (counts/liter) mg/L
ug/L
Count/L
Decay Constant (Infiltration) 1/hours 1/hours
Decay Constant (Pollutants) 1/days 1/days
Depression Storage inches millimeters
Depth feet meters
Diameter feet meters
Discharge Coefficient:
Orifice
dimensionless
dimensionless
Weir CFS/footn CMS/metern
Elevation feet meters
Evaporation inches/day millimeters/day
Flow CFS (cubic feet / second)
GPM (gallons / minute)
MGD (million gallons/day) CMS (cubic meters/second)
LPS (liters/second)
MLD (million liters/day)
Head feet meters
Hydraulic Conductivity inches/hour millimeters/hour
Infiltration Rate inches/hour millimeters/hour
Length feet meters
Manning’s n seconds/meter1/3 seconds/meter1/3^
Pollutant Buildup mass/length
mass/acre mass/length
mass/hectare
Rainfall Intensity inches/hour millimeters/hour
Rainfall Volume inches millimeters
Slope (Subcatchments) percent percent
Slope (Cross Section) rise/run rise/run
Street Cleaning Interval days days
Volume cubic feet cubic meters
Width feet meters

A.2 Soil Characteristics

Soil Texture Class K Ψ (^) φ FC WP
Sand 4.74 1.93 0.437 0.062 0.024
Loamy Sand 1.18 2.40 0.437 0.105 0.047
Sandy Loam 0.43 4.33 0.453 0.190 0.085
Loam 0.13 3.50 0.463 0.232 0.116
Silt Loam 0.26 6.69 0.501 0.284 0.135
Sandy Clay Loam 0.06 8.66 0.398 0.244 0.136
Clay Loam 0.04 8.27 0.464 0.310 0.187
Silty Clay Loam 0.04 10.63 0.471 0.342 0.210
Sandy Clay 0.02 9.45 0.430 0.321 0.221
Silty Clay 0.02 11.42 0.479 0.371 0.251
Clay 0.01 12.60 0.475 0.378 0.265
K = saturated hydraulic conductivity, in/hr
Ψ = suction head, in.
φ = porosity, fraction
FC = field capacity, fraction
WP = wilting point, fraction
Source: Rawls, W.J. et al., (1983). J. Hyd. Engr., 109:1316.
Note: The following relation between Ψ and K can be derived
from this table:
Ψ = 3.23 K-0.328 (R^2 = 0.9)

A.3 NRCS Hydrologic Soil Group Definitions

(^)
Saturated
Hydraulic
Conductivity
(in/hr)
Group Meaning

A

Low runoff potential.
Water is transmitted freely through the soil. Group A soils
typically have less than 10 percent clay and more than 90
percent sand or gravel and have gravel or sand textures.
1.42

B

Moderately low runoff potential.
Water transmission through the soil is unimpeded. Group B
soils typically have between 10 percent and 20 percent
clay and 50 percent to 90 percent sand and have loamy
sand or sandy loam textures.

0.57 – 1.42

Moderately high runoff potential.
Water transmission through the soil is somewhat restricted.
Group C soils typically have between 20 percent and 40
percent clay and less than 50 percent sand and have loam,
silt loam, sandy clay loam, clay loam, and silty clay loam
textures.

C 0.06 – 0.57

High runoff potential.
Water movement through the soil is restricted or very
restricted. Group D soils typically have greater than 40
percent clay, less than 50 percent sand, and have clayey
textures.

D < 0.06

Source: Hydrology National Engineering Handbook, Chapter 7, Natural Resources
Conservation Service, U.S. Department of Agriculture, January 2009.

A.4 SCS Curve Numbers

Land Use Description Hydrologic Soil Group
A B C D Cultivated land
Without conservation treatment
With conservation treatment

72

62

81

71

88

78

91

81

Pasture or range land
Poor condition
Good condition

68

39

79

61

86

74

89

80

Meadow
Good condition

30

58

71

78

Wood or forest land
Thin stand, poor cover, no mulch
Good cover^2

45

25

66

55

77

70

83

77

Open spaces, lawns, parks, golf
etc.
courses, cemeteries,^
Good condition: grass cover on
75% or more of the area

39

61

74

80

Fair condition: grass cover on
50-75% of the area

49

69

79

84

Commercial and business areas (85% impervious) 89 92 94 95 Industrial districts (72% impervious) 81 88 91 93 Residential^3
Average lot size (% Impervious^4 )
1/8 ac or less (65)
1/4 ac (38)
1/3 ac (30)
1/2 ac (25)
1 ac (20)

77

61

57

54

51

85

75

72

70

68

90

83

81

80

79

92

87

86

85

84

Paved parking lots, roofs, driveways, etc.^5 98 98 98 98 Streets and roads
Paved with curbs and storm sewers^5
Gravel
Dirt

98

76

72

98

85

82

98

89

87

98

91

89

Source: SCS Urban Hydrology for Small Watersheds, 2nd Ed., (TR-55), June 1986. Footnotes:
  1. Antecedent moisture condition II.
  2. Good cover is protected from grazing and litter and brush cover soil.
  3. Curve numbers are computed assuming that the runoff from the house and driveway is
    directed toward the street with a minimum of roof water directed to lawns where additional
    infiltration could occur.
  4. The remaining pervious areas (lawn) are considered to be in good pasture condition for these
    curve numbers.
  5. In some warmer climates of the country a curve number of 95 may be used.

A.5 Depression Storage

Impervious surfaces 0.05 - 0.10 inches
Lawns 0.10 - 0.20 inches
Pasture 0.20 inches
Forest litter 0.30 inches
Source: ASCE, (1992). Design & Construction of Urban Stormwater
Management Systems, New York, NY.

A.6 Manning’s n – Overland Flow

Surface n
Smooth asphalt 0.011
Smooth concrete 0.012
Ordinary concrete lining 0.013
Good wood 0.014
Brick with cement mortar 0.014
Vitrified clay 0.015
Cast iron 0.015
Corrugated metal pipes 0.024
Cement rubble surface 0.024
Fallow soils (no residue) 0.05
Cultivated soils
Residue cover < 20% 0.06
Residue cover > 20% 0.17
Range (natural) 0.13
Grass
Short, prairie
Dense

0.15

0.24

Bermuda grass 0.41
Woods
Light underbrush
Dense underbrush

0.40

0.80

Source: McCuen, R. et al. (1996), Hydrology, FHWA-SA-
96-067, Federal Highway Administration, Washington,
DC

A.7 Manning’s n – Closed Conduits

Conduit Material Manning n
Asbestos-cement pipe 0.011 - 0.015
Brick 0.013 - 0.017
Cast iron pipe
  • Cement-lined & seal coated
    0.011 – 0.015
    Concrete (monolithic)
  • Smooth forms
    0.012 – 0.014
  • Rough forms 0.015 – 0.017
    Concrete pipe 0.011 – 0.015
    Corrugated-metal pipe
    (1/2-in. x 2-2/3-in. corrugations)
  • Plain
    0.022 – 0.026
  • Paved invert 0.018 – 0.022
  • Spun asphalt lined 0.011 – 0.015
    Plastic pipe (smooth) 0.011 – 0.015
    Vitrified clay
  • Pipes
  • Liner plates

0.011 –

0.013 –

0.015

0.017

Source: ASCE (1982). Gravity Sanitary Sewer Design and Construction, ASCE Manual of
Practice No. 60, New York, NY.

A.8 Manning’s n – Open Channels

Channel Type Manning n
Lined Channels
  • Asphalt 0.013 – 0.017
  • Brick 0.012 – 0.018
  • Concrete 0.011 – 0.020
  • Rubble or riprap 0.020 – 0.035
  • Vegetal 0.030 – 0.40
    Excavated or dredged
  • Earth, straight and uniform 0.020 – 0.030
  • Earth, winding, fairly uniform 0.025 – 0.040
  • Rock 0.030 – 0.045
  • Unmaintained 0.050 – 0.140
    Natural channels (minor streams, top width at flood
    stage < 100 ft)
  • Fairly regular section 0.030 – 0.070
  • Irregular section with pools 0.040 – 0.100
Source: ASCE ( 1 982). Gravity Sanitary Sewer Design and Construction, ASCE Manual of
Practice No. 60, New York, NY.

A.9 Water Quality Characteristics of Urban Runoff viii

Constituent Event Mean Concentrations
TSS (mg/L) 180 - 548
BOD (mg/L) 12 - 19
COD (mg/L) 82 - 178
Total P (mg/L) 0.42 - 0. 88
Soluble P (mg/L) 0.15 - 0.28
TKN (mg/L) 1.90 - 4.18
NO2/NO3-N (mg/L) 0.86 - 2.2
Total Cu (ug/L) 43 - 11 8
Total Pb (ug/L) 182 - 443
Total Zn (ug/L) 202 - 633
Source: U.S. Environmental Protection Agency. (1983). Results of the
Nationwide Urban Runoff Program (NURP), Vol. 1, NTIS PB 84-185552),
Water Planning Division, Washington, DC.

A.10 Culvert Code Numbers

Circular Concrete
1 Square edge with headwall
2 Groove end with headwall
3 Groove end projecting
Circular Corrugated Metal Pipe
4 Headwall
5 Mitered to slope
6 Projecting
Circular Pipe, Beveled Ring Entrance
7 45 deg. bevels
8 33.7 deg. bevels
Rectangular Box; Flared Wingwalls
9 30-75 deg. wingwall flares
10 90 or 15 deg. wingwall flares
11 0 deg. wingwall flares (straight sides)
Rectangular Box;Flared Wingwalls and Top Edge Bevel:
12 45 deg flare; 0.43D top edge bevel
13 18-33.7 deg. flare; 0.083D top edge bevel
Rectangular Box, 90-deg Headwall, Chamfered / Beveled Inlet Edges
14 chamfered 3/4-in.
15 beveled 1/2-in/ft at 45 deg (1:1)
16 beveled 1-in/ft at 33.7 deg (1:1.5)
Rectangular Box, Skewed Headwall, Chamfered / Beveled Inlet Edges
17 3/4" chamfered edge, 45 deg skewed headwall
18 3/4" chamfered edge, 30 deg skewed headwall
19 3/4" chamfered edge, 15 deg skewed headwall
20 45 deg beveled edge, 10-45 deg skewed headwall
Rectangular Box, Non-offset Flared Wingwalls, 3/4" Chamfer at Top of Inlet
21 45 deg (1:1) wingwall flare
22 8.4 deg (3:1) wingwall flare
23 18.4 deg (3:1) wingwall flare, 30 deg inlet skew
Rectangular Box, Offset Flared Wingwalls, Beveled Edge at Inlet Top
24 45 deg (1:1) flare, 0.042D top edge bevel
25 33.7 deg (1.5:1) flare, 0.083D top edge bevel
26 18.4 deg (3:1) flare, 0.083D top edge bevel
Corrugated Metal Box
27 90 deg headwall
28 Thick wall projecting
29 Thin wall projecting Horizontal Ellipse Concrete
30 Square edge with headwall
31 Grooved end with headwall
32 Grooved end projecting Vertical Ellipse Concrete
33 Square edge with headwall
34 Grooved end with headwall
35 Grooved end projecting Pipe Arch, 18″ Corner Radius, Corrugated Metal
36 90 deg headwall
37 Mitered to slope
38 Projecting Pipe Arch, 18″ Corner Radius, Corrugated Metal
39 Projecting
40 No bevels
41 33.7 deg bevels Pipe Arch, 31″ Corner Radius,Corrugated Metal
42 Projecting
43 No bevels
44 33.7 deg. bevels Arch, Corrugated Metal
45 90 deg headwall
46 Mitered to slope
47 Thin wall projecting Circular Culvert
48 Smooth tapered inlet throat
49 Rough tapered inlet throat Elliptical Inlet Face
50 Tapered inlet, beveled edges
51 Tapered inlet, square edges
52 Tapered inlet, thin edge projecting Rectangular
53 Tapered inlet throat Rectangular Concrete
54 Side tapered, less favorable edges
55 Side tapered, more favorable edges
56 Slope tapered, less favorable edges
57 Slope tapered, more favorable edges

A.11 Culvert Entrance Loss Coefficients

Type of Structure and Design of Entrance Coefficient
  • Pipe, Concrete
    Projecting from fill, socket end (groove-end) 0.2
    Projecting from fill, sq. cut end 0.5
    Headwall or headwall and wingwalls:
    Socket end of pipe (groove-end) 0.2
    Square-edge 0.5
    Rounded (radius = D/12) 0.2
    Mitered to conform to fill slope 0.7
    *End-Section conforming to fill slope 0.5
    Beveled edges, 33.7 ° or 45 ° bevels 0.2
    Side- or slope-tapered inlet 0.2
  • Pipe or Pipe-Arch. Corrugated Metal
    Projecting from fill (no headwall) 0.9
    Headwall or headwall and wingwalls square-edge 0.5
    Mitered to conform to fill slope, paved or unpaved slope 0.7
    *End-Section conforming to fill slope 0.5
    Beveled edges, 33.7 ° or 45 ° bevels 0.2
    Side- or slope-tapered inlet 0.2
  • Box, Reinforced Concrete
    Headwall parallel to embankment (no wingwalls):
    Square-edged on 3 edges 0.5
    Rounded on 3 edges to radius of D/12 or B/12
    or beveled edges on 3 sides 0.2
    Wingwalls at 30 ° to 75 ° to barrel:
    Square-edged at crown 0.4
    Crown edge rounded to radius of D/12:
    or beveled top edge 0.2
    Wingwall at 10 ° to 25 ° to barrel:
    Square-edged at crown 0.5
    Wingwalls parallel (extension of sides):
    Square-edged at crown 0.7
    Side- or slope-tapered inlet 0.2
*Note: "End Sections conforming to fill slope," made of either metal or concrete, are the
sections commonly available from manufacturers. From limited hydraulic tests they are
equivalent in operation to a headwall in both inlet and outlet control. Some end sections,
incorporating a closed taper in their design have a superior hydraulic performance. These
latter sections can be designed using the information given for the beveled inlet.
Source: Federal Highway Administration (2005). Hydraulic Design of Highway Culverts,
Publication No. FHWA-NHI-01-020.

A.12 Standard Elliptical Pipe Sizes

Code Minor Axis (in) Major Axis (in) Minor Axis (mm) Major Axis (mm)
1 14 23 356 584
2 19 30 483 762
3 22 34 559 864
4 24 38 610 965
5 27 42 686 1067
6 29 45 737 1143
7 32 49 813 1245
8 34 53 864 1346
9 38 60 965 1524
10 43 68 1092 1727
11 48 76 1219 1930
12 53 83 1346 2108
13 58 91 1473 2311
14 63 98 1600 2489
15 68 106 1727 2692
16 72 113 1829 2870
17 77 121 1956 3073
18 82 128 2083 3251
19 87 136 2210 3454
20 92 143 2337 3632
21 97 151 2464 3835
22 106 166 2692 4216
23 116 180 2946 4572
Note: The Minor Axis is the maximum width for a vertical ellipse and the full depth for a horizontal
ellipse while the Major Axis is the maximum width for a horizontal ellipse and the full depth for a
vertical ellipse. Source: Concrete Pipe Design Manual, American Concrete Pipe Association, 2011
(www.concrete-pipe.org).

A.13 Standard Arch Pipe Sizes

Concrete Arch Pipes
Code Rise (in) Span (in) Rise (mm) Span (mm)
1 11 18 279 457
2 13.5 22 343 559
3 15.5 26 394 660
4 18 28.5 457 724
5 22.5 36.25 572 921
6 26.625 43.75 676 1111
7 31.3125 51.125 795 1299
8 36 58.5 914 1486
9 40 65 1016 1651
10 45 73 1143 1854
11 54 88 1372 2235
12 62 102 1575 2591
13 72 115 1829 2921
14 77.5 122 1969 3099
15 87.125 138 2213 3505
16 96.875 154 2461 3912
17 106.5 168.75 2705 4286
Corrugated Steel, 2-2/3 x 1/2″ Corrugation
Code Rise (in) Span (in) Rise (mm) Span (mm)
18 13 17 330 432
19 15 21 381 533
20 18 24 457 610
21 20 28 508 711
22 24 35 610 889
23 29 42 737 1067
24 33 49 838 1245
25 38 57 965 1448
26 43 64 1092 1626
27 47 71 1194 1803
28 52 77 1321 1956
29 57 83 1448 2108
Corrugated Steel, 3 x 1″ Corrugation
Code Rise (in) Span (in) Rise (mm) Span (mm)
(^30 31 40 787 1016)
(^31 36 46 914 1168)
(^32 41 53 1041 1346)
(^33 46 60 1168 1524)
(^34 51 66 1295 1676)
(^35 55 73 1397 1854)
(^36 59 81 1499 2057)
(^37 63 87 1600 2210)
(^38 67 95 1702 2413)
(^39 71 103 1803 2616)
(^40 75 112 1905 2845)
(^41 79 117 2007 2972)
(^42 83 128 2108 3251)
(^43 87 137 2210 3480)
(^44 91 142 2311 3607) Structural Plate, 18″ Corner Radius
Code Rise (in) Span (in) Rise (mm) Span (mm)
(^45 55 73 1397 1854)
(^46 57 76 1448 1930)
(^47 59 81 1499 2057)
(^48 61 84 1549 2134)
(^49 63 87 1600 2210)
(^50 65 92 1651 2337)
(^51 67 95 1702 2413)
(^52 69 98 1753 2489)
(^53 71 103 1803 2616)
(^54 73 106 1854 2692)
(^55 75 112 1905 2845)
(^56 77 114 1956 2896)
(^57 79 117 2007 2972)
(^58 81 123 2057 3124)
(^59 83 128 2108 3251)
(^60 85 131 2159 3327)
(^61 87 137 2210 3480)
(^62 89 139 2261 3531)
(^63 91 142 2311 3607)
(^64 93 148 2362 3759)
(^65 95 150 2413 3810)
(^66 97 152 2464 3861)
(^67 100 154 2540 3912)
(^68 101 161 2565 4089)
(^69 103 167 2616 4242)
(^70 105 169 2667 4293)
(^71 107 171 2718 4343)
(^72 109 178 2769 4521)
(^73 111 184 2819 4674)
(^74 113 186 2870 4724)
(^75 115 188 2921 4775)
(^76 118 190 2997 4826)
(^77 119 197 3023 5004)
(^78 121 199 3073 5055) Structural Plate, 31″ Corner Radius
Code Rise (in) Span (in) Rise (mm) Span (mm)
(^79 112 159 2845 4039)
(^80 114 162 2896 4115)
(^81 116 168 2946 4267)
(^82 118 170 2997 4318)
(^83 120 173 3048 4394)
(^84 122 179 3099 4547)
(^85 124 184 3150 4674)
(^86 126 187 3200 4750)
(^87 128 190 3251 4826)
(^88 130 195 3302 4953)
(^89 132 198 3353 5029)
(^90 134 204 3404 5182)
(^91 136 206 3454 5232)
(^92 138 209 3505 5309)
(^93 140 215 3556 5461)
(^94 142 217 3607 5512)
(^95 144 223 3658 5664)
(^96 146 225 3708 5715)
(^97 148 231 3759 5867)
(^98 150 234 3810 5944)
(^99 152 236 3861 5994)
(^100 154 239 3912 6071)
(^101 156 245 3962 6223)
(^102 158 247 4013 6274)
Source: Modern Sewer Design (Fourth Edition), American Iron and Steel Institute, Washington,
DC, 1999.

APPENDIX B – VISUAL OBJECT PROPERTIES

B.1 Rain Gage Properties

Name User-assigned rain gage name. X- Coordinate Horizontal location of the rain gage on the Study Area Map. If left blank
then the rain gage will not appear on the map. Y- Coordinate Vertical location of the rain gage on the Study Area Map. If left blank then
the rain gage will not appear on the map. Description Click the ellipsis button (or press Enter) to edit an optional description of
the rain gage. Tag (^) Optional label used to categorize or classify the rain gage.
Rain Format Format in which the rain data are supplied:
INTENSITY: each rainfall value is an average rate in inches/hour (or
mm/hour) over the recording interval,
VOLUME: each rainfall value is the volume of rain that fell in the recording
interval (in inches or millimeters),
CUMULATIVE: each rainfall value represents the cumulative rainfall that
has occurred since the start of the last series of non-zero values (in inches
or millimeters).
Rain Interval Recording time interval between gage readings in either decimal hours or
hours:minutes format.
Snow Catch Factor Factor that corrects gage readings for snowfall.
Data Source Source of rainfall data; either TIMESERIES for user-supplied time series
data or FILE for an external data file.
TIME SERIES
  • Series Name (^) Name of time series with rainfall data if Data Source selection was
    TIMESERIES; leave blank otherwise (double-click to edit the series).
    DATA FILE
  • File Name Name of external file containing rainfall data (see Section 11.3).
  • Station No. Recording gage station number.
  • Rain Units Depth units (IN or MM) for rainfall values in user-prepared files (other
    standard file formats have fixed units depending on the format).

B.2 Subcatchment Properties

Name User-assigned subcatchment name. X- Coordinate Horizontal location of the subcatchment’s centroid on the Study Area Map.
If left blank then the subcatchment will not appear on the map. Y- Coordinate Vertical location of the subcatchment’s centroid on the Study Area Map. If
left blank then the subcatchment will not appear on the map. Description Click the ellipsis button (or press Enter) to edit an optional description of
the subcatchment. Tag Optional label used to categorize or classify the subcatchment. Rain Gage Name of the rain gage associated with the subcatchment. Outlet Name of the node or subcatchment which receives the subcatchment’s
runoff. Area Area of the subcatchment , including any LID controls (acres or hectares). Width^1 Characteristic width of the overland flow path for sheet flow runoff (feet or
meters). % Slope Average percent slope of the subcatchment. % Imperv (^) Percent of land area (excluding the area used for LID controls) which is
impervious.
N- Imperv Manning’s n for overland flow over the impervious portion of the
subcatchment (see Section A.6 for typical values).
N- Perv Manning’s n for overland flow over the pervious portion of the
subcatchment (see Section A.6 for typical values).
Dstore-Imperv Depth of depression storage on the impervious portion of the
subcatchment (inches or millimeters) (see Section A.5 for typical values).
Dstore-Perv Depth of depression storage on the pervious portion of the subcatchment
(inches or millimeters) (see Section A.5 for typical values).
% Zero-Imperv Percent of the impervious area with no depression storage.
Subarea Routing Choice of internal routing of runoff between pervious and impervious
areas:
IMPERV: runoff from pervious area flows to impervious area,
PERV: runoff from impervious area flows to pervious area,
OUTLET: runoff from both areas flows directly to outlet.
Percent Routed Percent of runoff routed between subareas.
Infiltration Click the ellipsis button (or press Enter) to edit infiltration parameters for
the subcatchment.
LID Controls Click the ellipsis button (or press Enter) to edit the use of low impact
development controls in the subcatchment. Groundwater Click the ellipsis button (or press Enter) to edit groundwater flow
parameters for the subcatchment. Snow Pack Name of snow pack parameter set (if any) assigned to the subcatchment. Land Uses Click the ellipsis button (or press Enter) to assign land uses to the
subcatchment. Only needed if pollutant buildup/washoff modeled. Initial Buildup Click the ellipsis button (or press Enter) to specify initial quantities of
pollutant buildup over the subcatchment. Curb Length Total length of curbs in the subcatchment (any length units). Used only
when pollutant buildup is normalized to curb length. (^1) An initial estimate of the characteristic width is given by the subcatchment area divided by the
average maximum overland flow length. The maximum overland flow length is the length of the
flow path from the furthest drainage point of the subcatchment before the flow becomes
channelized. Maximum lengths from several different possible flow paths should be averaged.
These paths should reflect slow flow, such as over pervious surfaces, more than rapid flow over
pavement, for example. Adjustments should be made to the width parameter to produce good fits
to measured runoff hydrographs.

B.3 Junction Properties

Name (^) User-assigned junction name.
X- Coordinate Horizontal location of the junction on the Study Area Map. If left blank then
the junction will not appear on the map.
Y- Coordinate Vertical location of the junction on the Study Area Map. If left blank then
the junction will not appear on the map.
Description (^) Click the ellipsis button (or press Enter) to edit an optional description of
the junction.
Tag Optional label used to categorize or classify the junction.
Inflows Click the ellipsis button (or press Enter) to assign external direct, dry
weather or RDII inflows to the junction.
Treatment (^) Click the ellipsis button (or press Enter) to edit a set of treatment functions
for pollutants entering the node.
Invert El. Invert elevation of the junction (feet or meters).
Max. Depth Maximum depth of junction (i.e., from ground surface to invert) (feet or
meters). If zero, then the distance from the invert to the top of the highest
connecting link will be used.
Initial Depth Depth of water at the junction at the start of the simulation (feet or
meters).
Surcharge Depth Additional depth of water beyond the maximum depth that is allowed
before the junction floods (feet or meters). This parameter can be used to
simulate bolted manhole covers or force main connections.
Ponded Area Area occupied by ponded water atop the junction after flooding occurs (sq.
feet or sq. meters). If the Allow Ponding simulation o ption is turned on, a
non-zero value of this parameter will allow ponded water to be stored and
subsequently returned to the conveyance system when capacity exists.

B.4 Outfall Properties

Name (^) User-assigned outfall name.
X- Coordinate Horizontal location of the outfall on the Study Area Map. If left blank then
the outfall will not appear on the map.
Y- Coordinate Vertical location of the outfall on the Study Area Map. If left blank then the
outfall will not appear on the map.
Description (^) Click the ellipsis button (or press Enter) to edit an optional description of
the outfall.
Tag Optional label used to categorize or classify the outfall.
Inflows Click the ellipsis button (or press Enter) to assign external direct, dry
weather or RDII inflows to the outfall.
Treatment (^) Click the ellipsis button (or press Enter) to edit a set of treatment functions
for pollutants entering the node.
Invert El. Invert elevation of the outfall (feet or meters).
Tide Gate YES – tide gate present to prevent backflow
NO – no tide gate present
Route To Optional name of a subcatchment that receives the outfall’s discharge.
Type Type of outfall boundary condition:
FREE: outfall stage determined by minimum of critical flow depth and
normal flow depth in the connecting conduit
NORMAL: outfall stage based on normal flow depth in connecting conduit
FIXED: outfall stage set to a fixed value
TIDAL: outfall stage given by a table of tide elevation versus time of day
TIMESERIES: outfall stage supplied from a time series of elevations.
Fixed Stage Water elevation for a FIXED type of outfall (feet or meters).
Tidal Curve Name Name of the Tidal Curve relating water elevation to hour of the day for a
TIDAL outfall (double-click to edit the curve).
Time Series Name Name of time series containing time history of outfall elevations for a
TIMESERIES outfall (double-click to edit the series).

B.5 Flow Divider Properties

Name (^) User-assigned divider name.
X- Coordinate Horizontal location of the divider on the Study Area Map. If left blank then
the divider will not appear on the map.
Y- Coordinate Vertical location of the divider on the Study Area Map. If left blank then the
divider will not appear on the map.
Description (^) Click the ellipsis button (or press Enter) to edit an optional description of
the divider.
Tag Optional label used to categorize or classify the divider.
Inflows Click the ellipsis button (or press Enter) to assign external direct, dry
weather or RDII inflows to the divider.
Treatment (^) Click the ellipsis button (or press Enter) to edit a set of treatment functions
for pollutants entering the node.
Invert El. Invert elevation of the divider (feet or meters).
Max. Depth Maximum depth of divider (i.e., from ground surface to invert) (feet or
meters). See description for Junctions.
Initial Depth (^) Depth of water at the divider at the start of the simulation (feet or meters).
Surcharge Depth Additional depth of water beyond the maximum depth that is allowed
before the divider floods (feet or meters).
Ponded Area Area occupied by ponded water atop the junction after flooding occurs (sq.
feet or sq. meters). See description for Junctions.
Diverted Link (^) Name of link which receives the diverted flow.
Type Type of flow divider. Choices are:
CUTOFF ( diverts all inflow above a defined cutoff value),
OVERFLOW (diverts all inflow above the flow capacity of the non-diverted
link),
TABULAR (uses a Diversion Curve to express diverted flow as a function
of the total inflow),
WEIR ( uses a weir equation to compute diverted flow).
CUTOFF DIVIDER
  • Cutoff Flow Cutoff flow value used for a CUTOFF divider (flow units).
TABULAR DIVIDER
  • Curve Name Name of Diversion Curve used with a TABULAR divider (double-click to
    edit the curve).

WEIR DIVIDER

  • Min. Flow Minimum flow at which diversion begins for a WEIR divider (flow units).
  • Max. Depth Vertical height of WEIR opening (feet or meters)
  • Coefficient Product of WEIR’s discharge coefficient and its length. Weir coefficients
    are typically in the range of 2.65 to 3.10 per foot, for flows in CFS.
Note: Flow dividers are operational only for Steady Flow and Kinematic Wave flow routing. For
Dynamic Wave flow routing they behave as Junction nodes.

B.6 Storage Unit Properties

Name (^) User-assigned storage unit name.
X- Coordinate Horizontal location of the storage unit on the Study Area Map. If left blank
then the storage unit will not appear on the map.
Y- Coordinate Vertical location of the storage unit on the Study Area Map. If left blank
then the storage unit will not appear on the map.
Description (^) Click the ellipsis button (or press Enter) to edit an optional description of
the storage unit.
Tag Optional label used to categorize or classify the storage unit.
Inflows Click the ellipsis button (or press Enter) to assign external direct, dry
weather or RDII inflows to the storage unit.
Treatment (^) Click the ellipsis button (or press Enter) to edit a set of treatment functions
for pollutants within the storage unit.
Invert El. Elevation of the bottom of the storage unit (feet or meters).
Max. Depth Maximum depth of the storage unit (feet or meters).
Initial Depth Initial depth of water in the storage unit at the start of the simulation (feet
or meters).
Evap. Factor The fraction of the potential evaporation from the storage unit’s water
surface that is actually realized.
Seepage Loss Click the ellipsis button (or press Enter) to specify optional soil properties
that determine seepage loss through the bottom and sloped sides of the
storage unit.
Storage Curve Method of describing how the surface area of the storage unit varies with
water depth:
FUNCTIONAL uses the function
Area = A×(Depth)B + C
to describe how surface area varies with depth;
TABULAR uses a tabulated area versus depth curve.
In either case, depth is measured in feet (or meters) above the bottom and
surface area in sq. feet (or sq. meters).
FUNCTIONAL
Coeff. (^) A- value in the functional relationship between surface area and storage
depth.
Exponent B- value in the functional relationship between surface area and storage
depth.
Constant C- value in the functional relationship between surface area and storage
depth.

TABULAR

Curve Name Name of the Storage Curve containing the relationship between surface
area and storage depth (double-click to edit the curve). The curve will be
extrapolated outwards to meet the unit’s Max. Depth if need be.

B.7 Conduit Properties

Name (^) User-assigned conduit name.
Inlet Node Name of node on the inlet end of the conduit (which is normally the end at
higher elevation).
Outlet Node Name of node on the outlet end of the conduit (which is normally the end
at lower elevation).
Description (^) Click the ellipsis button (or press Enter) to edit an optional description of
the conduit.
Tag Optional label used to categorize or classify the conduit.
Shape Click the ellipsis button (or press Enter) to edit the geometric properties of
the conduit’s cross section.
Max. Depth (^) Maximum depth of the conduit’s cross section (feet or meters).
Length Conduit length (feet or meters).
Roughness Manning’s roughness coefficient (see Section A.7 for closed conduit
values or Section A.8 for open channel values).
Inlet Offset Depth or elevation of the conduit invert above the node invert at the
upstream end of the conduit (feet or meters). See note below.
Outlet Offset Depth or elevation of the conduit invert above the node invert at the
downstream end of the conduit (feet or meters). See note below.
Initial Flow Initial flow in the conduit (flow units).
Maximum Flow Maximum flow allowed in the conduit (flow units) – use 0 or leave blank if
not applicable.
Entry Loss Coeff. Head loss coefficient associated with energy losses at the entrance of the
conduit. For culverts, refer to Table A11.
Exit Loss Coeff. Head loss coefficient associated with energy losses at the exit of the
conduit. For culverts, use a value of 1.0
Avg. Loss Coeff. (^) Head loss coefficient associated with energy losses along the length of
the conduit.
Flap Gate YES if a flap gate exists that prevents backflow through the conduit, or NO
if no flap gate exists.
Culvert Code Code number of inlet geometry if conduit is a culvert – leave blank
otherwise. Culvert code numbers are listed in Table A10. NOTE: Conduits and flow regulators (orifices, weirs,
and outlets) can be offset some distance above the
invert of their connecting end nodes. There are two
different conventions available for specifying the
location of these offsets. The Depth convention uses
the offset distance from the node’s invert (distance between  and  in the figure on the right). The
Elevation convention uses the absolute elevation of the offset location (the elevation of point  in the figure).
The choice of convention can be made on the Status
Bar of SWMM’s main window or on the Node/Link Properties page of the Project Defaults dialog. (^)

B.8 Pump Properties

Name User-assigned pump name. Inlet Node Name of node on the inlet side of the pump. Outlet Node Name of node on the outlet side of the pump. Description Click the ellipsis button (or press Enter) to edit an optional description of
the pump. Tag Optional label used to categorize or classify the pump. Pump Curve Name of the Pump Curve which contains the pump’s operating data
(double-click to edit the curve). Enter * for an Ideal pump. Initial Status Status of the pump (ON or OFF) at the start of the simulation. Startup Depth (^) Depth at inlet node when pump turns on (feet or meters). Enter 0 if not
applicable.
Shutoff Depth Depth at inlet node when pump shuts off (feet or meters). Enter 0 if not
applicable.

B.9 Orifice Properties

Name (^) User-assigned orifice name.
Inlet Node Name of node on the inlet side of the orifice.
Outlet Node Name of node on the outlet side of the orifice.
Description Click the ellipsis button (or press Enter) to edit an optional description of
the orifice.
Tag Optional label used to categorize or classify the orifice.
Type Type of orifice (SIDE or BOTTOM).
Shape Orifice shape (CIRCULAR or RECT_CLOSED).
Height Height of orifice opening when fully open (feet or meters). Corresponds to
the diameter of a circular orifice or the height of a rectangular orifice.
Width (^) Width of rectangular orifice when fully opened (feet or meters).
Inlet Offset Depth or elevation of bottom of orifice above invert of inlet node (feet or
meters – see note below table of Conduit Properties).
Discharge Coeff. Discharge coefficient (unitless). A typical value is 0.65.
Flap Gate YES if a flap gate exists which prevents backflow through the orifice, or
NO if no flap gate exists.
Time to Open /
Close
The time it takes to open a closed (or close an open) gated orifice in
decimal hours. Use 0 or leave blank if timed openings/closings do not
apply. Use Control Rules to adjust gate position.

B.10 Weir Properties

Name (^) User-assigned weir name.
Inlet Node Name of node on inlet side of weir.
Outlet Node Name of node on outlet side of weir.
Description Click the ellipsis button (or press Enter) to edit an optional description of
the weir.
Tag Optional label used to categorize or classify the weir.
Type Weir type: TRANSVERSE, SIDEFLOW, V- NOTCH, TRAPEZOIDAL or
ROADWAY.
Height Vertical height of weir opening (feet or meters).
Length Horizontal length of weir opening (feet or meters).
Side Slope (^) Slope (width-to-height) of side walls for a V- NOTCH or TRAPEZOIDAL
weir.
Inlet Offset Depth or elevation of bottom of weir opening from invert of inlet node
(feet or meters – see note below table of Conduit Properties).
Discharge Coeff.^1 Discharge coefficient for flow through the central portion of the weir (for
flow in CFS when using US units or CMS when using SI units).
Flap Gate YES if the weir has a flap gate that prevents backflow, NO otherwise..
End Coeff. Discharge coefficient for flow through the triangular ends of a
TRAPEZOIDAL weir. See the recommended values for V-notch weirs.
End Contractions Number of end contractions for a TRANSVERSE or TRAPEZOIDAL
weir whose length is shorter than the channel it is placed in. Values will
be either 0 , 1 , or 2 depending if no ends, one end, or both ends are
beveled in from the side walls.
Can Surcharge YES if the weir can surcharge (have an upstream water level higher
than the height of the opening) or NO if it cannot.
ROADWAY WEIR
Road Width Width of roadway and shoulders (feet or meters)
Road Surface Type of road surface: PAVED or GRAVEL.
(^1) Typical values are: 3.33 US (1.84 SI) for sharp crested transverse weirs, 2.5 – 3.3 US (1.38 –
1.83 SI) for broad crested rectangular weirs, 2.4 – 2.8 US (1.35 – 1.55 SI) for V-notch (triangular)
weirs. Discharge over Roadway weirs with a non-zero road width is computed using the FHWA
HDS-5 method.

B.11 Outlet Properties

Name (^) User-assigned outlet name.
Inlet Node Name of node on inflow side of outlet.
Outlet Node Name of node on discharge side of outlet.
Description Click the ellipsis button (or press Enter) to edit an optional description of
the outlet.
Tag Optional label used to categorize or classify the outlet.
Inlet Offset Depth or elevation of outlet above inlet node invert (feet or meters – see
note below table of Conduit Properties).
Flap Gate YES if a flap gate exists which prevents backflow through the outlet, or
NO if no flap gate exists.
Rating Curve Method of defining flow (Q) as a function of depth or head (y) across the
outlet.
FUNCTIONAL/DEPTH uses a power function (Q = AyB) t o describe this
relation where y is the depth of water above the outlet’s opening at the
inlet node.
FUNCTIONAL/HEAD uses the same power function except that y is the
difference in head across the outlet’s nodes.
TABULAR/DEPTH uses a tabulated curve of flow versus depth of water
above the outlet’s opening at the inlet node.
TABULAR/HEAD uses a tabulated curve of flow versus difference in head
across the outlet’s nodes.
FUNCTIONAL
  • Coefficient Coefficient (A) for the functional relationship between depth or head and
    flow rate.
  • Exponent Exponent (B) used for the functional relationship between depth or head
    and flow rate.
TABULAR
  • Curve Name Name of Rating Curve containing the relationship between depth or head
    and flow rate (double-click to edit the curve).

B.12 Map Label Properties

Text (^) Text of label.
X- Coordinate Horizontal location of the upper-left corner of the label on the Study Area
Map.
Y- Coordinate Vertical location of the upper-left corner of the label on the Study Area
Map.
Anchor Node (^) Name of node (or subcatchment) that anchors the label’s position when
the map is zoomed in (i.e., the pixel distance between the node and the
label remains constant). Leave blank if anchoring is not used.
Font Click the ellipsis button (or press Enter) to modify the font used to draw
the label.

APPENDIX C – SPECIALIZED PROPERTY EDITORS

C.1 Aquifer Editor

The Aquifer Editor is invoked whenever a new aquifer object is created or an existing aquifer
object is selected for editing. It contains the following data fields:
Name
User-assigned aquifer name.
Porosity
Volume of voids / total soil volume
(volumetric fraction).
Wilting Point
Soil moisture content at which plants
cannot survive (volumetric fraction).
Field Capacity
Soil moisture content after all free
water has drained off (volumetric
fraction).
Conductivity
Soil's saturated hydraulic conductivity
(in/hr or mm/hr).
Conductivity Slope
Average slope of log(conductivity)
versus soil moisture deficit (porosity
minus moisture content) curve
(unitless).
Tension Slope
Average slope of soil tension versus soil moisture content curve (inches or mm). Upper Evaporation Fraction
Fraction of total evaporation available for evapotranspiration in the upper unsaturated zone. Lower Evaporation Depth
Maximum depth below the surface at which evapotranspiration from the lower saturated zone can
still occur (ft or m). Lower Groundwater Loss Rate
Rate of percolation to deep groundwater when the water table reaches the ground surface (in/hr
or mm/hr). Bottom Elevation
Elevation of the bottom of the aquifer (ft or m). Water Table Elevation
Elevation of the water table in the aquifer at the start of the simulation (ft or m). Unsaturated Zone Moisture
Moisture content of the unsaturated upper zone of the aquifer at the start of the simulation
(volumetric fraction) (cannot exceed soil porosity). Upper Evaporation Pattern
Name of the monthly time pattern of adjustments applied to the upper evaporation fraction
(optional – leave blank if not applicable).

C.2 Climatology Editor

The Climatology Editor is used to enter values for various climate-related variables required by
certain SWMM simulations. The dialog is divided into six tabbed pages, where each page
provides a separate editor for a specific category of climate data. Temperature Page The Temperature page of the Climatology Editor dialog is used to specify the source of
temperature data used for snowmelt computations. It is also used to select a climate file as a
possible source for evaporation rates. There are three choices available: No Data: Select this choice if snowmelt is not being simulated and evaporation rates are
not based on data in a climate file. Time Series: Select this choice if the variation in temperature over the simulation period will be
described by one of the project’s time series. Also, enter (or select) the name of
the time series. Click the button to make the Time Series Editor appear for
the selected time series.
External
Climate File: Select this choice if min/max daily temperatures will be read from an external
climate file (see Section 11.4). Also enter the name of the file (or click the
button to search for the file). If you want to start reading the climate file at a
particular date in time that is different than the start date of the simulation (as
specified in the Simulation Options), check off the “Start Reading File at” box and
enter a starting date (month/day/year) in the date entry field next to it. Use this
choice if you want daily evaporation rates to be estimated from daily
temperatures or be read directly from the file.
Evaporation Page The Evaporation page of the Climatology Editor dialog is used to supply evaporation rates, in
inches/day (or mm/day), for a study area. There are five choices for specifying these rates that
are selected from the Source of Evaporation Rates combo box: Constant Value:
Use this choice if evaporation remains constant over time. Enter the value in the edit box
provided. Time Series:
Select this choice if evaporation rates will be specified in a time series. Enter or select the name of the time series in the dropdown combo box provided. Click the button to bring up the Time
Series editor for the selected series. Note that for each date specified in the time series, the
evaporation rate remains constant at the value supplied for that date until the next date in the
series is reached (i.e., interpolation is not used on the series). Directly From Climate File:
This choice indicates that daily evaporation rates will be read from the same climate file that was
specified for temperature. Enter values for monthly pan coefficients in the data grid provided. Monthly Averages:
Use this choice to supply an average rate for each month of the year. Enter the value for each
month in the data grid provided. Note that rates remain constant within each month. Computed from Temperatures:
The Hargreaves method will be used to compute daily evaporation rates from the daily air
temperature record contained in the external climate file specified on the Temperature page of
the dialog. This method also uses the site’s latitude, which can be entered on the Snowmelt page
of the dialog even if snow melt is not being simulated. Evaporate Only During Dry Periods:
Select this option if evaporation can only occur during periods with no precipitation. In addition this page allows the user to specify an optional Monthly Soil Recovery Pattern. This
is a time pattern whose factors adjust the rate at which infiltration capacity is recovered during
periods with no precipitation. It applies to all subcatchments for any choice of infiltration method.
For example, if the normal infiltration recovery rate was 1% during a specific time period and a
pattern factor of 0.8 applied to this period, then the actual recovery rate would be 0.8%. The Soil
Recovery Pattern allows one to account for seasonal soil drying rates. In principle, the variation in
pattern factors should mirror the variation in evaporation rates but might be influenced by other factors such as seasonal groundwater levels. The button is used to launch the Time Pattern
Editor for the selected pattern. Wind Speed Page The Wind Speed page of the Climatology Editor dialog is used to provide average monthly wind
speeds. These are used when computing snowmelt rates under rainfall conditions. Melt rates
increase with increasing wind speed. Units of wind speed are miles/hour for US units and
km/hour for metric units. There are two choices for specifying wind speeds: Climate File Data: Wind speeds will be read from the same climate file that was specified
for temperature. Monthly Averages: Wind speed is specified as an average value that remains constant in
each month of the year. Enter a value for each month in the data grid
provided. The default values are all zero. Snowmelt Page The Snowmelt page of the Climatology Editor dialog is used to supply values for the following
parameters related to snow melt calculations: Dividing Temperature Between Snow and Rain
Enter the temperature below which precipitation falls as snow instead of rain. Use degrees F for
US units or degrees C for metric units. ATI (Antecedent Temperature Index) Weight
This parameter reflects the degree to which heat transfer within a snow pack during non-melt
periods is affected by prior air temperatures. Smaller values reflect a thicker surface layer of snow
which results in reduced rates of heat transfer. Values must be between 0 and 1, and the default
is 0.5. Negative Melt Ratio
This is the ratio of the heat transfer coefficient of a snow pack during non-melt conditions to the
coefficient during melt conditions. It must be a number between 0 and 1. The default value is 0.6. Elevation Above MSL
Enter the average elevation above mean sea level for the study area, in feet or meters. This value
is used to provide a more accurate estimate of atmospheric pressure. The default is 0.0, which
results in a pressure of 29.9 inches Hg. The effect of wind on snow melt rates during rainfall
periods is greater at higher pressures, which occur at lower elevations. Latitude
Enter the latitude of the study area in degrees North. This number is used when computing the
hours of sunrise and sunset, which in turn are used to extend min/max daily temperatures into
continuous values. It is also used to compute daily evaporation rates from daily temperatures.
The default is 50 degrees North. Longitude Correction
This is a correction, in minutes of time, between true solar time and the standard clock time. It
depends on a location’s longitude (θ) and the standard meridian of its time zone (SM) through the
expression 4(θ-SM). This correction is used to adjust the hours of sunrise and sunset when
extending daily min/max temperatures into continuous values. The default value is 0. Areal Depletion Page The Areal Depletion page of the Climatology Editor Dialog is used to specify points on the Areal
Depletion Curves for both impervious and pervious surfaces within a project’s study area. These
curves define the relation between the area that remains snow covered and snow pack depth.
Each curve is defined by 10 equal increments of relative depth ratio between 0 and 0.9. (Relative
depth ratio is the ratio of an area’s current snow depth to the depth at which there is 100% areal
coverage). Enter values in the data grid provided for the fraction of each area that remains snow covered at
each specified relative depth ratio. Valid numbers must be between 0 and 1, and be increasing
with increasing depth ratio. Clicking the Natural Area button fills the grid with values that are typical of natural areas. Clicking
the No Depletion button will fill the grid with all 1’s, indicating that no areal depletion occurs. This
is the default for new projects. Adjustments Page The Adjustments page of the Climatology Editor Dialog is used to supply a set of monthly
adjustments applied to the temperature, evaporation rate, rainfall, and soil hydraulic conductivity
that SWMM uses at each time step of a simulation:
  • The monthly Temperature adjustment (plus or minus in either degrees F or C) is added to
    the temperature value that SWMM would otherwise use in a specific month of the year.
  • The monthly Evaporation adjustment (plus or minus in either in/day or mm/day) is added
    to the evaporation rate value that SWMM would otherwise use in a specific month of the
    year.
  • The monthly Rainfall adjustment is a multiplier applied to the precipitation value that
    SWMM would otherwise use in a specific month of the year.
  • The monthly Conductivity adjustment is a multiplier applied to the soil hydraulic
    conductivity used compute rainfall infiltration, groundwater percolation, and exfiltration
    from channels and storage units.
The same adjustment is applied for each time period within a given month and is repeated for that
month in each subsequent year being simulated. Leaving a monthly adjustment blank means that
there is no adjustment made in that month.

C.3 Control Rules Editor

The Control Rules Editor is invoked whenever a new control rule is created or an existing rule is
selected for editing. The editor contains a memo field where the entire collection of control rules is
displayed and can be edited. Control Rule Format Each control rule is a series of statements of the form: RULE ruleID IF condition_1
AND condition_2
OR condition_3
AND condition_4
Etc. THEN action_1
AND action_2
Etc.
ELSE action_3
AND action_4
Etc. PRIORITY value where keywords are shown in boldface and ruleID is an ID label assigned to the rule,
condition_n is a Condition Clause, action_n is an Action Clause, and value is a priority value (e.g., a number from 1 to 5). The formats used for Condition and Action clauses are
discussed below. Only the RULE, IF and THEN portions of a rule are required; the ELSE and PRIORITY portions
are optional. Blank lines between clauses are permitted and any text to the right of a semicolon is considered a
comment. When mixing AND and OR clauses, the OR operator has higher precedence than AND, i.e.,
IF A or B and C
is equivalent to
IF (A or B) and C.
If the interpretation was meant to be
IF A or (B and C)
then this can be expressed using two rules as in
IF A THEN …
IF B and C THEN … The PRIORITY value is used to determine which rule applies when two or more rules require that
conflicting actions be taken on a link. A conflicting rule with a higher priority value has precedence
over one with a lower value (e.g., PRIORITY 5 outranks PRIORITY 1). A rule without a priority
value always has a lower priority than one with a value. For two rules with the same priority value,
the rule that appears first is given the higher priority. Condition Clauses A Condition Clause of a control rule has the following formats: object id attribute relation value
object id attribute relation object id attribute where:
object = a category of object
id = the object’s ID label
attribute = an attribute or property of the object
relation = a relational operator (=, <>, <, <=, >, >=)
value = an attribute value Some examples of condition clauses are: NODE N23 DEPTH > 10
NODE N23 DEPTH > NODE N25 DEPTH
PUMP P45 STATUS = OFF
SIMULATION CLOCKTIME = 22:45:00 The objects and attributes that can appear in a condition clause are as follows:
Object Attributes Value
DEPTH
HEAD
VOLUME
INFLOW
numerical value
numerical value
numerical value
numerical value

NODE

FLOW

DEPTH

TIMEOPEN

TIMECLOSED

numerical value
numerical value
decimal hours or hr:min
decimal hours or hr:min

LINK

STATUS

TIMEOPEN

TIMECLOSED

OPEN or CLOSED
decimal hours or hr:min
decimal hours or hr:min

CONDUIT

STATUS

SETTING

FLOW

TIMEOPEN

TIMECLOSED

ON or OFF
pump curve multiplier
numerical value
decimal hours or hr:min
decimal hours or hr:min

PUMP

ORIFICE

SETTING

TIMEOPEN

TIMECLOSED

fr action open
decimal hours or hr:min
decimal hours or hr:min
WEIR

SETTING

TIMEOPEN

TIMECLOSED

fr action open
decimal hours or hr:min
decimal hours or hr:min
OUTLET

SETTING

TIMEOPEN

TIMECLOSED

rating curve multiplier
decimal hours or hr:min
decimal hours or hr:min
SIMULATION TIME elapsed time in decimal hours or
hr:min:sec

SIMULATION

DATE

MONTH

DAY

CLOCKTIME

month/day/year
month of year (January = 1)
day of week (Sunday = 1)
time of day in hr:min:sec
TIMEOPEN is the duration a link has been in an OPEN or ON state or have its SETTING be greater
than zero; TIMECLOSED is the duration it has remained in a CLOSED or OFF state or have its
SETTING be zero. Action Clauses An Action Clause of a control rule can have one of the following formats: PUMP id STATUS = ON/OFF
PUMP/ORIFICE/WEIR/OUTLET id SETTING = value where the meaning of SETTING depends on the object being controlled:
 for Pumps it is a multiplier applied to the flow computed from the pump curve,
 for Orifices it is the fractional amount that the orifice is fully open,
 for Weirs it is the fractional amount of the original freeboard that exists (i.e., weir control
is accomplished by moving the crest height up or down),
 for Outlets it is a multiplier applied to the flow computed from the outlet's rating curve.
Some examples of action clauses are: PUMP P67 STATUS = OFF ORIFICE O212 SETTING = 0.5 Modulated Controls Modulated controls are control rules that provide for a continuous degree of control applied to a
pump or flow regulator as determined by the value of some controller variable, such as water
depth at a node, or by time. The functional relation between the control setting and the controller
variable can be specified by using a Control Curve, a Time Series, or a PID Controller. Some
examples of modulated control rules are: RULE MC1
IF NODE N2 DEPTH >= 0
THEN WEIR W25 SETTING = CURVE C25 RULE MC2
IF SIMULATION TIME > 0
THEN PUMP P12 SETTING = TIMESERIES TS101 RULE MC3
IF LINK L33 FLOW <> 1.6
THEN ORIFICE O12 SETTING = PID 0.1 0.0 0.0 Note how a modified form of the action clause is used to specify the name of the control curve,
time series or PID parameter set that defines the degree of control. A PID parameter set contains
three values — a proportional gain coefficient, an integral t ime (in minutes), and a derivative time
(in minutes). Also, by convention the controller variable used in a Control Curve or PID Controller
will always be the object and attribute named in the last condition clause of the rule. As an
example, in rule MC1 above Curve C25 would define how the fractional setting at Weir W25 varied with the water depth at Node N2. In rule MC3, the PID controller adjusts the opening of
Orifice O12 to maintain a flow of 1.6 in Link L33. PID Controllers A PID (Proportional-Integral-Derivative) Controller is a generic closed-loop control scheme that
tries to maintain a desired set-point on some process variable by computing and applying a
corrective action that adjusts the process accordingly. In the context of a hydraulic conveyance
system a PID controller might be used to adjust the opening on a gated orifice to maintain a
target flow rate in a specific conduit or to adjust a variable speed pump to maintain a desired
depth in a storage unit. The classical PID controller has the form:






= + ∫ +
dt
)t(de
Td)(e
T
1
)t(eK)t(m d
i
p ττ^ where m(t) = controller output, Kp = proportional coefficient (gain), Ti = integral time, Td =
derivative time, e(t) = error (difference between setpoint and observed variable value), and t =
time. The performance of a PID controller is determined by the values assigned to the coefficients
Kp, Ti, and Td. The controller output m(t) has the same meaning as a link setting used in a rule’s Action Clause
while dt is the current flow routing time step in minutes. Because link settings are relative values
(with respect to either a pump’s standard operating curve or to the full opening height of an orifice
or weir) the error e(t) used by the controller is also a relative value. It is defined as the difference
between the control variable setpoint x* and its value at time t, x(t), normalized to the setpoint
value: e(t) = (x* – x(t)) / x*. Note that for direct action control, where an increase in the link setting causes an increase in the
controlled variable, the sign of Kp must be positive. For reverse action control, where the
controlled variable decreases as the link setting increases, the sign of Kp must be negative. The
user must recognize whether the control is direct or reverse action and use the proper sign on Kd
accordingly. For example, adjusting an orifice opening to maintain a desired downstream flow is
direct action. Adjusting it to maintain an upstream water level is reverse action. Controlling a
pump to maintain a fixed wet well water level would be reverse action while using it to maintain a
fixed downstream flow is direct action.

C.4 Cross-Section Editor

The Cross-Section Editor dialog is used to specify the shape and dimensions of a conduit’s cross-
section. When a shape is selected from the image list an appropriate set of edit fields appears for
describing the dimensions of that shape. Length dimensions are in units of feet for US units and
meters for SI units. Slope values represent ratios of horizontal to vertical distance. The Barrels
field specifies how many identical parallel conduits exist between its end nodes. The Force Main shape option is a circular conduit that uses either the Hazen-Williams or Darcy-
Weisbach formulas to compute friction losses for pressurized flow during Dynamic Wave flow
routing. In this case the appropriate C-factor (for Hazen-Williams) or roughness height (for Darcy-
Weisbach) is supplied as a cross-section property. The choice of friction loss equation is made on
the Dynamic Wave Simulation Options dialog. Note that a conduit does not have to be assigned a
Force Main shape for it to pressurize. Any of the other closed cross-section shapes can
potentially pressurize and thus function as force mains using the Manning equation to compute
friction losses. If a Custom shaped section is chosen, a drop-down edit box will appear where you can enter or
select the name of a Shape Curve that will be used to define the geometry of the section. This
curve specifies how the width of the cross-section varies with height, where both width and height
are scaled relative to the section’s maximum depth. This allows the same shape curve to be used for conduits of differing sizes. Clicking the Edit button next to the shape curve box will bring
up the Curve Editor where the shape curve’s coordinates can be edited. If an Irregular shaped section is chosen, a drop-down edit box will appear where you can enter or
select the name of a Transect object that describes the cross-section’s geometry. Clicking the Edit button next to the edit box will bring up the Transect Editor from which you can edit the
transect data.

C.5 Curve Editor

The Curve Editor dialog is invoked whenever a new curve object is created or an existing curve
object is selected for editing. The editor adapts itself to the category of curve being edited
(Storage, Tidal, Diversion, Pump, or Rating). To use the Curve Editor:
 Enter values for the following data entry fields:
Name Name of the curve.
Type (Pump Curves Only). Choice of pump curve type as described in
Section 3.2
Description Optional comment or description of what the curve represents. Click
the button to launch a multi-line comment editor if more than one
line is needed.
Data Grid The curve's X,Y data.
 Click the View button to see a graphical plot of the curve drawn in a separate window.
 If additional rows are needed in the Data Grid, simply press the Enter key when in the
last row.
 Right-clicking over the Data Grid will make a popup Edit menu appear. It contains
commands to cut, copy, insert, and paste selected cells in the grid as well as options to
insert or delete a row.
You can also click the Load button to load in a curve that was previously saved to file or click the
Save button to save the current curve’s data to a file.

C.6 Groundwater Flow Editor

The Groundwater Flow Editor dialog is invoked when the Groundwater property of a
subcatchment is being edited. It is used to link a subcatchment to both an aquifer and to a node
of the drainage system that exchanges groundwater with the aquifer. It also specifies coefficients
that determine the rate of lateral groundwater flow between the aquifer and the node. These
coefficients (A1, A2, B1, B2, and A3) appear in the following equation that computes groundwater
flow as a function of groundwater and surface water levels: 푄푄퐿퐿=퐴퐴1(퐻퐻푔푔푔푔−퐻퐻푐푐푐푐)퐵퐵1−퐴퐴2(퐻퐻푠푠푔푔−퐻퐻푐푐푐푐)퐵퐵2+퐴퐴 3 퐻퐻푔푔푔푔퐻퐻푠푠푔푔 where:
QL = lateral groundwater flow (cfs per acre or cms per hectare)
Hgw = height of saturated zone above bottom of aquifer (ft or m)
Hsw = height of surface water at receiving node above aquifer bottom (ft or m)
Hcb = height of channel bottom above aquifer bottom (ft or m).
Note that QL can also be expressed in inches/hr for US units. The rate of percolation to deep groundwater, QD, in in/hr (or mm/hr) is given by the following
equation:

푄푄퐷퐷=퐿퐿퐿퐿퐿퐿퐿퐿 �

퐻퐻퐺퐺퐺퐺

퐻퐻퐺퐺퐺퐺

where LGLR is the lower groundwater loss rate parameter assigned to the subcatchment’s
aquifer (in/hr or mm/hr) and HGS is the distance from the ground surface to the aquifer bottom (ft
or m). In addition to the standard lateral flow equation, the dialog allows one to define a custom equation
whose results will be added onto those of the standard equation. One can also define a custom
equation for deep groundwater flow that will replace the standard one. Finally, the dialog offers
the option to override certain parameters that were specified for the aquifer to which the
subcatchment belongs. The properties listed in the editor are as follows: Aquifer Name
Name of the aquifer object that describes the subsurface soil properties, thickness, and initial
conditions. Leave this field blank if you want the subcatchment not to generate any groundwater
flow. Receiving Node
Name of node that receives groundwater from the aquifer. Surface Elevation
Elevation of ground surface for the subcatchment that lies above the aquifer in feet or meters. Groundwater Flow Coefficient
Value of A1 in the groundwater flow formula. Groundwater Flow Exponent
Value of B1 in the groundwater flow formula. Surface Water Flow Coefficient
Value of A2 in the groundwater flow formula. Surface Water Flow Exponent
Value of B2 in the groundwater flow formula. Surface-GW Interaction Coefficient
Value of A3 in the groundwater flow formula. Surface Water Depth
Fixed depth of surface water above receiving node’s invert (feet or meters). Set to zero if surface
water depth will vary as computed by flow routing. Threshold Water Table Elevation
Minimum water table elevation that must be reached before any flow occurs (feet or meters).
Leave blank to use the receiving node’s invert elevation. Aquifer Bottom Elevation
Elevation of the bottom of the aquifer below this particular subcatchment (feet or meters). Leave
blank to use the value from the parent aquifer. Initial Water Table Elevation
Initial water table elevation at the start of the simulation for this particular subcatchment (feet or
meters). Leave blank to use the value from the parent aquifer. Unsaturated Zone Moisture
Moisture content of the unsaturated upper zone above the water table for this particular
subcatchment at the start of the simulation (volumetric fraction). Leave blank to use the value
from the parent aquifer. Custom Lateral Flow Equation
Click the ellipsis button (or press Enter) to launch the Custom Groundwater Flow Equation editor
for lateral groundwater flow QL (see section C.7). The equation supplied by this editor will be used
in addition to the standard equation to compute groundwater outflow from the subcatchment. Custom Deep Flow Equation
Click the ellipsis button (or press Enter) to launch the Custom Groundwater Flow Equation editor
for deep groundwater flow QD. The equation supplied by this editor will be used to replace the
standard equation for deep groundwater flow. The coefficients supplied to the groundwater flow equations must be in units that are consistent
with the groundwater flow units, which can either be cfs/acre (equivalent to inches/hr) for US units
or cms/ha for SI units.
Note that elevations are used to specify the ground surface, water table height, and
aquifer bottom in the dialog’s data entry fields but that the groundwater flow equation
uses depths above the aquifer bottom.
If groundwater flow is simply proportional to the difference in groundwater and surface
water heads, then set the Groundwater and Surface Water Flow Exponents (B1 and B2)
to 1.0, set the Groundwater Flow Coefficient (A1) to the proportionality factor, set the
Surface Water Flow Coefficient (A2) to the same value as A1, and set the Interaction
Coefficient (A3) to zero.
Note that when conditions warrant, the groundwater flux can be negative, simulating flow
into the aquifer from the channel, in the manner of bank storage. An exception occurs
when A3 ≠ 0, since the surface water - groundwater interaction term is usually derived
from groundwater flow models that assume unidirectional flow. Otherwise, to ensure that
negative fluxes will not occur, one can make A1 greater than or equal to A2, B1 greater
than or equal to B2, and A3 equal to zero.
To completely replace the standard groundwater flow equation with the custom equation,
set all of the standard equation coefficients to 0.

C.7 Groundwater Equation Editor

The Groundwater Equation Editor is used to supply a custom equation for computing
groundwater flow between the saturated sub-surface zone of a subcatchment and either a node
in the conveyance network (lateral flow) or to a deeper groundwater aquifer (deep flow). It is
invoked from the Groundwater Flow Editor form. For lateral groundwater flow the result of evaluating the custom equation will be added onto the
result of the standard equation. To replace the standard equation completely set all of its
coefficients to 0. Remember that lateral groundwater flow units are cfs/acre (equivalent to
inches/hr) for US units and cms/ha for metric units. The following symbols can be used in the equation:
Hgw (for height of the groundwater table)
Hsw (for height of the surface water)
Hcb (for height of the channel bottom)
Hgs (for height of the ground surface)
Phi (for porosity of the subsurface soil)
Theta (for moisture content of the upper unsaturated zone)
Ks (for saturated hydraulic conductivity in inches/hr or mm/hr)
K (for hydraulic conductivity at the current moisture content in inches/hr or mm/hr)
Fi (for infiltration rate from the ground surface in inches/hr or mm/hr)
Fu (for percolation rate from the upper unsaturated zone in inches/hr or mm/hr)
A (for subcatchment area in acres or hectares)
where all heights are relative to the aquifer’s bottom elevation in feet (or meters). The STEP function can be used to have flow only when the groundwater level is above a certain
threshold. For example, the expression: 0.001 * (Hgw – 5) * STEP(Hgw – 5) would generate flow only when Hgw was above 5. See Section C.22 (Treatment Editor) for a list
of additional math functions that can be used in a groundwater flow expression.

C.8 Infiltration Editor

The Infiltration Editor dialog is used to specify values for the parameters that describe the rate at
which rainfall infiltrates into the upper soil zone in a subcatchment’s pervious area. It is invoked
when editing the Infiltration property of a subcatchment. The infiltration parameters depend on
which infiltration model was selected for the project: Horton, Green-Ampt, or Curve Number. The
choice of infiltration model can be made either by editing the project’s Simulation Options (see
Section 8.1) or by changing the project’s Default Properties (see Section 5.4). Horton Infiltration Parameters The following data fields appear in the Infiltration Editor for Horton infiltration: Max. Infil. Rate
Maximum infiltration rate on the Horton curve (in/hr or mm/hr). Representative values are as
follows:
A. DRY soils (with little or no vegetation):
 Sandy soils: 5 in/hr
 Loam soils: 3 in/hr
 Clay soils: 1 in/hr
B. DRY soils (with dense vegetation):
 Multiply values in A. by 2
C. MOIST soils:
 Soils which have drained but not dried out (i.e., field capacity):
Divide values from A and B by 3.
 Soils close to saturation:
Choose value close to minimum infiltration rate.
 Soils which have partially dried out:
Divide values from A and B by 1.5 - 2.5.
Min. Infil. Rate
Minimum infiltration rate on the Horton curve (in/hr or mm/hr). Equivalent to the soil’s saturated
hydraulic conductivity. See the Soil Characteristics Table in Section A.2 for typical values. Decay Const.
Infiltration rate decay constant for the Horton curve (1/hours). Typical values range between 2
and 7. Drying Time
Time in days for a fully saturated soil to dry completely. Typical values range from 2 to 14 days. Max. Infil. Vol.
Maximum infiltration volume possible (inches or mm, 0 if not applicable). It can be estimated as
the difference between a soil’s porosity and its wilting point times the depth of the infiltration zone. Green-Ampt Infiltration Parameters The following data fields appear in the Infiltration Editor for Green-Ampt infiltration: Suction Head
Average value of soil capillary suction along the wetting front (inches or mm). Conductivity
Soil saturated hydraulic conductivity (in/hr or mm/hr). Initial Deficit
Fraction of soil volume that is initially dry (i.e., difference between soil porosity and initial moisture
content). For a completely drained soil, it is the difference between the soil’s porosity and its field
capacity. Typical values for all of these parameters can be found in the Soil Characteristics Table in
Section A.2. Curve Number Infiltration Parameters The following data fields appear in the Infiltration Editor for Curve Number infiltration: Curve Number
This is the SCS curve number which is tabulated in the publication SCS Urban Hydrology for
Small Watersheds, 2nd Ed., (TR-55), June 1986. Consult the Curve Number Table (Section A.4)
for a listing of values by soil group, and the accompanying Soil Group Table (Section A.3) for the
definitions of the various groups. Conductivity
This property has been deprecated and is no longer used. Drying Time
The number of days it takes a fully saturated soil to dry. Typical values range between 2 and 14
days.

C.9 Inflows Editor ix

The Inflows Editor dialog is used to assign Direct, Dry Weather, and RDII inflow into a node of the
drainage system. It is invoked whenever the Inflows property of a Node object is selected in the
Property Editor. The dialog consists of three tabbed pages that provide a special editor for each
type of inflow. Direct Inflows Page The Direct page on the Inflows Editor dialog is used to specify the time history of direct external
flow and water quality entering a node of the drainage system. These inflows are represented by
both a constant and time varying component as follows: Inflow at time t = (baseline value)(baseline pattern factor) + (scale factor)(time series value at time t) The page contains the following input fields that define the properties of this relation: Constituent
Selects the constituent (FLOW or one of the project’s specified pollutants) whose direct inflow will
be described. Baseline
Specifies the value of the constant baseline component of the constituent’s inflow. For FLOW, the
units are the project’s flow units. For pollutants, the units are the pollutant’s concentration units if
inflow is a concentration, or can be any mass flow units if the inflow is a mass flow (see
Conversion Factor below). If left blank then no baseline inflow is assumed. Baseline Pattern
An optional Time Pattern whose factors adjust the baseline inflow on either an hourly, daily, or monthly basis (depending on the type of time pattern specified). Clicking the button will bring
up the Time Pattern Editor dialog for the selected time pattern. If left blank, then no adjustment is
made to the baseline inflow. Time Series
Specifies the name of the time series that contains inflow data for the selected constituent. If left
blank then no direct inflow will occur for the selected constituent at the node in question. You can click the button to bring up the Time Series Editor dialog for the selected time series. Scale Factor
A multiplier used to adjust the values of the constituent’s inflow time series. The baseline value is
not adjusted by this factor. The scale factor can have several uses, such as allowing one to easily
change the magnitude of an inflow hydrograph while keeping its shape the same, without having
to re-edit the entries in the hydrograph time series. Or it can allow a group of nodes sharing the
same time series to have their inflows behave in a time-synchronized fashion while letting their
individual magnitudes be different. If left blank the scale factor defaults to 1.0. Inflow Type
For pollutants, selects the type of inflow data contained in the time series as being either a
concentration (mass/volume) or mass flow rate (mass/time). This field does not appear for FLOW
inflow. Conversion Factor
A numerical factor used to convert the units of pollutant mass flow rate in the time series data into
concentration mass units per second. For example, if the time series data were in pounds per day
and the pollutant concentration defined in the project was mg/L, then the conversion factor value
would be ( 45 3, 590 mg/lb) / (86400 sec/day) = 5.25 (mg/sec) per (lb/day). More than one constituent can be edited while the dialog is active by simply selecting another
choice for the Constituent property. However, if the Cancel button is clicked then any changes
made to all constituents will be ignored.
If a pollutant is assigned a direct inflow in terms of concentration, then one must also
assign a direct inflow to flow, otherwise no pollutant inflow will occur. An exception is at
submerged outfalls where pollutant intrusion can occur during periods of reverse flow. If
pollutant inflow is defined in terms of mass, then a flow inflow time series is not required.
Dry Weather Inflows Page The Dry Weather page of the Inflows Editor dialog is used to specify a continuous source of dry
weather flow entering a node of the drainage system. The page contains the following input fields: Constituent
Selects the constituent (FLOW or one of the project’s specified pollutants) whose dry weather
inflow will be specified. Average Value
Specifies the average (or baseline) value of the dry weather inflow of the constituent in the
relevant units (flow units for flow, concentration units for pollutants). Leave blank if there is no dry
weather flow for the selected constituent. Time Patterns
Specifies the names of the time patterns to be used to allow the dry weather flow to vary in a
periodic fashion by month of the year, by day of the week, and by time of day (for both weekdays
and weekends). One can either type in a name or select a previously defined pattern from the
dropdown list of each combo box. Up to four different types of patterns can be assigned. You can click the button next to each Time Pattern field to edit the respective pattern. More than one constituent can be edited while the dialog is active by simply selecting another
choice for the Constituent property. However, if the Cancel button is clicked then any changes
made to all constituents will be ignored. RDII Inflow Page The RDII Inflow page of the Inflows Editor dialog form is used to specify RDII (Rainfall Dependent
Infiltration/Inflow) for the node in question. The page contains the following two input fields: Unit Hydrograph Group
Enter (or select from the dropdown list) the name of the Unit Hydrograph group that applies to the
node in question. The unit hydrographs in the group are used in combination with the group’s
assigned rain gage to develop a time series of RDII inflows per unit area over the period of the
simulation. Leave this field blank to indicate that the node receives no RDII inflow. Clicking the
button will launch the Unit Hydrograph Editor for the UH group specified.
Sewershed Area
Enter the area (in acres or hectares) of the sewershed that contributes RDII to the node in
question. Note this area will typically be only a small, localized portion of the subcatchment area
that contributes surface runoff to the node.

C.10 Initial Buildup Editor

(^)
The Initial Buildup Editor is invoked from the Property Editor when editing the Initial Buildup
property of a subcatchment. It specifies the amount of pollutant buildup existing over the
subcatchment at the start of the simulation. The editor consists of a data entry grid with two
columns. The first column lists the name of each pollutant in the project and the second column
contains edit boxes for entering the initial buildup values. If no buildup value is supplied for a
pollutant, it is assumed to be 0. The units for buildup are either pounds per acre when US units
are in use or kilograms per hectare when SI metric units are in use.
If a non-zero value is specified for the initial buildup of a pollutant, it will override any initial
buildup computed from the Antecedent Dry Days parameter specified on the Dates page of the
Simulation Options dialog.

C.11 Land Use Editor

The Land Use Editor dialog is used to define a category of land use for the study area and to
define its pollutant buildup and washoff characteristics. The dialog contains three tabbed pages of
land use properties:
 General Page (provides land use name and street sweeping parameters)
 Buildup Page (defines rate at which pollutant buildup occurs)
 Washoff Page (defines rate at which pollutant washoff occurs)
General Page The General page of the Land Use Editor dialog describes the following properties of a particular
land use category: Land Use Name
The name assigned to the land use. Description
An optional comment or description of the land use (click the ellipsis button or press Enter to
edit). Street Sweeping Interval
Days between street sweeping within the land use. Street Sweeping Availability
Fraction of the buildup of all pollutants that is available for removal by sweeping. Last Swept
Number of days since last swept at the start of the simulation. If street sweeping does not apply to the land use, then the last three properties can be left blank. Buildup Page The Buildup page of the Land Use Editor dialog describes the properties associated with pollutant
buildup over the land during dry weather periods. These consist of: Pollutant
Select the pollutant whose buildup properties are being edited. Function
The type of buildup function to use for the pollutant. The choices are NONE for no buildup, POW
for power function buildup, EXP for exponential function buildup SAT for saturation function
buildup, and EXT for buildup supplied by an external time series. See the discussion of Pollutant
Buildup in Section 3.3.9 Land Uses for explanations of these different functions. Select NONE if no
buildup occurs. Max. Buildup
The maximum buildup that can occur, expressed as lbs (or kg) of the pollutant per unit of the
normalizer variable (see below). This is the same as the C1 coefficient used in the buildup
formulas discussed in Section 3.3.9. The following two properties apply to the POW, EXP, and SAT buildup functions: Rate Constant
The time constant that governs the rate of pollutant buildup. This is the C2 coefficient in the
Power and Exponential buildup formulas discussed in Section 3.3.9. For Power buildup its units
are mass / days raised to a power, while for Exponential buildup its units are 1/days. Power/Sat. Constant
The exponent C3 used in the Power buildup formula, or the half-saturation constant C2 used in
the Saturation buildup formula discussed in Section 3.3.9. For the latter case, its units are days. The following two properties apply to the EXT (External Time Series) option: Scaling Factor
A multiplier used to adjust the buildup rates listed in the time series. Time Series
The name of the Time Series that contains buildup rates (as mass per normalizer per day). Normalizer
The variable to which buildup is normalized on a per unit basis. The choices are either land area
(in acres or hectares) or curb length. Any units of measure can be used for curb length, as long
as they remain the same for all subcatchments in the project. When there are multiple pollutants, the user must select each pollutant separately from the
Pollutant dropdown list and specify its pertinent buildup properties. Washoff Page The Washoff page of the Land Use Editor dialog describes the properties associated with
pollutant washoff over the land use during wet weather events. These consist of: Pollutant
The name of the pollutant whose washoff properties are being edited. Function
The choice of washoff function to use for the pollutant. The choices are:
 NONE no washoff
 EXP exponential washoff
 RC rating curve washoff
 EMC event-mean concentration washoff.
The formula for each of these functions is discussed in Section 3.3.9 Land Uses under the
Pollutant Washoff topic. Coefficient
This is the value of C1 in the exponential and rating curve formulas, or the event-mean
concentration. Exponent
The exponent used in the exponential and rating curve washoff formulas. Cleaning Efficiency
The street cleaning removal efficiency (percent) for the pollutant. It represents the fraction of the
amount that is available for removal on the land use as a whole (set on the General page of the
editor) which is actually removed. BMP Efficiency
Removal efficiency (percent) associated with any Best Management Practice that might have
been implemented. The washoff load computed at each time step is simply reduced by this
amount. As with the Buildup page, each pollutant must be selected in turn from the Pollutant dropdown list
and have its pertinent washoff properties defined.

C.12 Land Use Assignment Editor

(^)
The Land Use Assignment editor is invoked from the Property Editor when editing the Land Uses
property of a subcatchment. Its purpose is to assign land uses to the subcatchment for water
quality simulations. The percent of land area in the subcatchment covered by each land use is
entered next to its respective land use category. If the land use is not present its field can be left
blank. The percentages entered do not necessarily have to add up to 100.

C.13 LID Control Editor

The LID Control Editor is used to define a low impact development control that can be deployed
throughout a study area to store, infiltrate, and evaporate subcatchment runoff. The design of the
control is made on a per-unit-area basis so that it can be placed in any number of subcatchments
at different sizes or number of replicates. The editor contains the following data entry fields: Control Name
A name used to identify the particular LID control. LID Type
The generic type of LID being defined (bio-retention cell, rain garden, green roof, infiltration
trench, permeable pavement, rain barrel, or vegetative swale). Process Layers
These are a tabbed set of pages containing data entry fields for the vertical layers and drain
system that comprise an LID control. They include some combination of the following, depending
on the type of LID selected: Surface Layer, Pavement Layer, Soil Layer, Storage Layer, and
Drain System or Drainage Mat. Surface Layer Properties The Surface Layer page of the LID Control Editor is used to describe the surface properties of all
types of LID controls except rain barrels. Surface layer properties include: Berm Height (or Storage Depth)
When confining walls or berms are present this is the maximum depth to which water can pond
above the surface of the unit before overflow occurs (in inches or mm). For Rooftop
Disconnection it is the roof’s depression storage depth, and f or Vegetative Swales it is the height
of the trapezoidal cross section. Vegetative Volume Fraction
The fraction of the volume within the storage depth filled with vegetation. This is the volume
occupied by stems and leaves, not their surface area coverage. Normally this volume can be
ignored, but may be as high as 0.1 to 0.2 for very dense vegetative growth. Surface Roughness
Manning’s n for overland flow over surface soil cover, pavement, roof surface or vegetative swale.
Use 0 for other types of LIDs. Surface Slope
Slope of a roof surface, pavement surface or vegetative swale (percent). Use 0 for other types of
LIDs. Swale Side Slope
Slope (run over rise) of the side walls of a vegetative swale’s cross section. This value is ignored
for other types of LIDs.
If either Surface Roughness or Surface Slope values are 0 then any ponded water that
exceeds the surface storage depth is assumed to completely overflow the LID control
within a single time step.
Pavement Layer Properties The Pavement Layer page of the LID Control Editor supplies values for the following properties
of a permeable pavement LID: Thickness
The thickness of the pavement layer (inches or mm). Typical values are 4 to 6 inches (100 to 150
mm). Void Ratio
The volume of void space relative to the volume of solids in the pavement for continuous systems
or for the fill material used in modular systems. Typical values for pavements are 0.12 to 0.21.
Note that porosity = void ratio / (1 + void ratio). Impervious Surface Fraction
Ratio of impervious paver material to total area for modular systems; 0 for continuous porous
pavement systems. Permeability
Permeability of the concrete or asphalt used in continuous systems or hydraulic conductivity of
the fill material (gravel or sand) used in modular systems (in/hr or mm/hr). The permeability of
new porous concrete or asphalt is very high (e.g., hundreds of in/hr) but can drop off over time
due to clogging by fine particulates in the runoff (see below). Clogging Factor
Number of pavement layer void volumes of runoff treated it takes to completely clog the
pavement. Use a value of 0 to ignore clogging. Clogging progressively reduces the pavement’s
permeability in direct proportion to the cumulative volume of runoff treated. If one has an estimate of the number of years it takes to fully clog the system (Yclog), the
Clogging Factor can be computed as: Yclog * Pa * CR * (1 + VR) * (1 – ISF) / (T * VR) where Pa
is the annual rainfall amount over the site, CR is the pavement’s capture ratio (area that
contributes runoff to the pavement divided by area of the pavement itself), VR is the system’s
Void Ratio, ISF is the Impervious Surface Fraction, and T is the pavement layer Thickness. As an example, suppose it takes 5 years to clog a continuous porous pavement system that
serves an area where the annual rainfall is 36 inches/year. If the pavement is 6 inches thick, has
a void ratio of 0.2 and captures runoff only from its own surface, then the Clogging Factor is 5 x
36 x (1 + 0.2) / 6 / 0.2 = 180. Soil Layer properties The Soil Layer page of the LID Control Editor describes the properties of the engineered soil
mixture used in bio-retention types of LIDs and the optional sand layer beneath permeable
pavement. These properties are: Thickness
The thickness of the soil layer (inches or mm). Typical values range from 18 to 36 inches (450 to
900 mm) for rain gardens, street planters and other types of land-based bio-retention units, but
only 3 to 6 inches (75 to 150 mm) for green roofs. Porosity
The volume of pore space relative to total volume of soil (as a fraction). Field Capacity
Volume of pore water relative to total volume after the soil has been allowed to drain fully (as a
fraction). Below this level, vertical drainage of water through the soil layer does not occur. Wilting Point
Volume of pore water relative to total volume for a well dried soil where only bound water remains
(as a fraction). The moisture content of the soil cannot fall below this limit. Conductivity
Hydraulic conductivity for the fully saturated soil (in/hr or mm/hr). Conductivity Slope
Slope of the curve of log(conductivity) versus soil moisture content (dimensionless). Typical
values range from 30 to 60. It can be estimated from a standard soil grain size analysis as
0.48(%Sand) + 0.85(%Clay). Suction Head
The average value of soil capillary suction along the wetting front (inches or mm). This is the
same parameter as used in the Green-Ampt infiltration model.
Porosity, field capacity, conductivity and conductivity slope are the same soil properties
used for Aquifer objects when modeling groundwater, while suction head is the same
parameter used for Green-Ampt infiltration. Except here they apply to the special soil
mixture used in a LID unit rather than the site's naturally occurring soil. See Appendix A.2
Soil Characteristics for typical values of these properties.
Storage Layer Properties The Storage Layer page of the LID Control Editor describes the properties of the crushed stone
or gravel layer used in bio-retention cells, permeable pavement systems, and infiltration trenches
as a bottom storage/drainage layer. It is also used to specify the height of a rain barrel (or
cistern). The following data fields are displayed: Thickness (or Barrel Height)
This is the thickness of a gravel layer or the height of a rain barrel (inches or mm). Crushed stone
and gravel layers are typically 6 to 18 inches (150 to 450 mm) thick while single family home rain
barrels range in height from 24 to 36 inches (600 to 900 mm). The following data fields do not apply to Rain Barrels. Void Ratio
The volume of void space relative to the volume of solids in the layer. Typical values range from
0.5 to 0.75 for gravel beds. Note that porosity = void ratio / (1 + void ratio). Seepage Rate
The rate at which water seeps into the native soil below the layer (in inches/hour or
mm/hour).This would typically be the Saturated Hydraulic Conductivity of the surrounding
subcatchment if Green-Ampt infiltration is used or the Minimum Infiltration Rate for Horton
infiltration. If there is an impermeable floor or liner below the layer then use a value of 0. Clogging Factor
Total volume of treated runoff it takes to completely clog the bottom of the layer divided by the
void volume of the layer. Use a value of 0 to ignore clogging. Clogging progressively reduces the
Infiltration Rate in direct proportion to the cumulative volume of runoff treated and may only be of
concern for infiltration trenches with permeable bottoms and no under drains. Storage Drain Properties LID storage layers can contain an optional drainage system that collects water entering the layer
and conveys it to a conventional storm drain or other location (which can be different than the
outlet of the LID’s subcatchment). Drain flow can also be returned it to the pervious area of the
LID’s subcatchment. The drain can be offset some distance above the bottom of the storage
layer, to allow some volume of runoff to be stored (and eventually infiltrated) before any excess is
captured by the drain. For Rooftop Disconnection, the drain system consists of the roof’s gutters
and downspouts that have some maximum conveyance capacity. The Drain page of the LID Control Editor describes the properties of this system. It contains the
following data entry fields: Drain Coefficient and Drain Exponent
The drain coefficient C and exponent n determines the rate of flow through a drain as a function
of the height of stored water above the drain’s offset. The following equation is used to compute
this flow rate (per unit area of the LID unit):
푞푞=퐶퐶ℎ푛푛
where q is outflow (in/hr or mm/hr) and h is the height of saturated media above the drain (inches
or mm). A typical value for n would be 0.5 (making the drain act like an orifice). Note that the units
of C depend on the unit system being used as well as the value assigned to n. If the layer has
no drain then set C to 0 Drain Offset Height
This is the height of the drain line above the bottom of a storage layer or rain barrel (inches or
mm). Drain Delay (for Rain Barrels only)
The number of dry weather hours that must elapse before the drain line in a rain barrel is opened
(the line is assumed to be closed once rainfall begins). A value of 0 signifies that the barrel’s drain
line is always open and drains continuously. This parameter is ignored for other types of LIDs. Flow Capacity (for Rooftop Disconnection only)
This is the maximum flow rate that the roof’s gutters and downspouts can handle (in inches/hour
or mm/hour) before overflowing. This is the only drain parameter used for Rooftop Disconnection. There are several things to keep in mind when specifying the parameters of an LID’s underdrain:
  • If the storage layer that contains the drain has an impermeable bottom then it’s best to
    place the drain at the bottom with a zero offset. Otherwise, to allow the full storage
    volume to fill before draining occurs, one would place the drain at the top of the storage
    layer.
  • If the storage layer has no drain then set the drain coefficient to 0.
  • If the drain can carry whatever flow enters the storage layer up to some specific limit then
    set the drain coefficient to the limit and the drain exponent to 0.
  • If the underdrain consists of slotted pipes where the slots act as orifices, then the drain
    exponent would be 0.5 and the drain coefficient would be 60,000 times the ratio of total
    slot area to LID area. For example, drain pipe with five 1/4″ diameter holes per foot
    spaced 50 feet apart would have an area ratio of 0.000035 and a drain coefficient of 2.
  • If the goal is to drain a fully saturated unit in a specific amount of time then set the drain
    exponent to 0.5 (to represent orifice flow) and the drain coefficient to 2D1/2/T where D is
    the distance from the drain to the surface plus any berm height (in inches or mm) and T is
    the time in hours to drain. For example, to drain a depth of 36 inches in 12 hours requires
    a drain coefficient of 1. If this drain consisted of the slotted pipes described in the
    previous bullet, whose coefficient was 2, then a flow regulator, such as a cap orifice,
    would have to be placed on the drain outlet to achieve the reduced flow rate.
Drainage Mat Properties Green Roofs usually contain a drainage mat or plate that lies below the soil media and above the
roof structure. Its purpose is to convey any water that drains through the soil layer off of the roof.
The Drainage Mat page of the LID Control Editor for Green Roofs lists the properties of this layer
which include: Thickness
The thickness of the mat or plate (inches or mm). It typically ranges between 1 to 2 inches. Void Fraction
The ratio of void volume to total volume in the mat. It typically ranges from 0.5 to 0.6. Roughness
This is the Manning’s n constant used to compute the horizontal flow rate of drained water
through the mat. It is not a standard product specification provided by manufacturers and
therefore must be estimated. Previous modeling studies have suggested using a relatively high
value such as from 0.1 to 0.4.

C.14 LID Group Editor

The LID Group Editor is invoked when the LID Controls property of a Subcatchment is selected
for editing. It is used to identify a group of previously defined LID controls that will be placed
within the subcatchment, the sizing of each control, and what percent of runoff from the non-LID
portion of the subcatchment each should treat. The editor displays the current group of LIDs placed in the subcatchment along with buttons for
adding an LID unit, editing a selected unit, and deleting a selected unit. These actions can also
be chosen by hitting the Insert key, the Enter key, and the Delete key, respectively. Selecting
Add or Edit will bring up an LID Usage Editor where one can enter values for the data fields
shown in the Group Editor. Note that the total % of Area for all of the LID units within a subcatchment must not exceed
100%. The same applies to % From Impervious. Refer to the LID Usage Editor for the meaning
of these parameters.

C.15 LID Usage Editor

The LID Usage Editor is invoked from a subcatchment’s LID Group Editor to specify how a
particular LID control will be deployed within the subcatchment. It contains the following data
entry fields: Control Name
The name of a previously defined LID control to be used in the subcatchment. (LID controls are
added to a project by using the Project Browser.) LID Occupies Full Subcatchment
Select this checkbox option if the LID control occupies the full subcatchment (i.e., the LID is
placed in its own separate subcatchment and accepts runoff from upstream subcatchments). Area of Each Unit
The surface area devoted to each replicate LID unit (sq. ft or sq. m). If the LID Occupies Full
Subcatchment box is checked, then this field becomes disabled and will display the total
subcatchment area divided by the number of replicate units. (See Section 3.3.14 LID Controls for
options on placing LIDs within subcatchments.) The label below this field indicates how much of
the total subcatchment area is devoted to the particular LID being deployed and gets updated as
changes are made to the number of units and area of each unit. Number of Replicate Units
The number of equal size units of the LID practice (e.g., the number of rain barrels) deployed
within the subcatchment. Surface Width Per Unit
The width of the outflow face of each identical LID unit (in ft or m). This parameter applies to
roofs, pavement, trenches, and swales that use overland flow to convey surface runoff off of the
unit. It can be set to 0 for other LID processes, such as bio-retention cells, rain gardens, and rain
barrels that simply spill any excess captured runoff over their berms. % Initially Saturated
For bio-r etention cells, rain gardens, and green roofs this is the degree to which the unit’s soil is
initially filled with water (0 % saturation corresponds to the wilting point moisture content, 100 %
saturation has the moisture content equal to the porosity). The storage zone beneath the soil
zone of the cell is assumed to be completely dry. For other types of LIDs it corresponds to the
degree to which their storage zone is initially filled with water. % of Impervious Area Treated
The percent of the impervious portion of the subcatchment’s non-LID area whose runoff is treated
by the LID practice. (E.g., if rain barrels are used to capture roof runoff and roofs represent 60%
of the impervious area, then the impervious area treated is 60%). If the LID unit treats only direct
rainfall, such as with a green roof or roof disconnection, then this value should be 0. If the LID
takes up the entire subcatchment then this field is ignored. Send Drain Flow To
Provide the name of the Node or Subcatchment that receives any drain flow produced by the LID
unit. This field can be left blank if this flow goes to the same outlet as the LID unit’s
subcatchment. Return All Outflow to Pervious Area
Select this option if outflow from the LID unit should be routed back onto the pervious area of the
subcatchment that contains it. If drain outflow was selected to be routed to a different location
than the subcatchment outlet then only surface outflow will be returned. Otherwise both surface
and drain flow will be returned. Selecting this option would be a common choice to make for Rain
Barrels, Rooftop Disconnection and possibly Green Roofs. Detailed Report File
The name of an optional file where detailed time series results for the LID will be written. Click the browse button to select a file using the standard Windows File Save dialog or click the delete button to remove any detailed reporting. The detailed report file will be a tab delimited text file
that can be easily opened and viewed with any text editor or spreadsheet program (such as
Microsoft Excel) outside of SWMM.

C.16 Pollutant Editor

The Pollutant Editor is invoked when a new pollutant object is created or an existing pollutant is
selected for editing. It contains the following fields: Name
The name assigned to the pollutant. Units
The concentration units (mg/L, ug/L, or #/L (counts/L)) in which the pollutant concentration is
expressed. Rain Concentration
Concentration of the pollutant in rain water (concentration units). GW Concentration
Concentration of the pollutant in ground water (concentration units). Initial Concentration
Concentration of the pollutant throughout the conveyance system at the start of the simulation. I&I Concentration
Concentration of the pollutant in any Infiltration/Inflow (concentration units). DWF Concentration
Concentration of the pollutant in any dry weather sanitary flow (concentration units). This value
can be overridden f or any specific node of the conveyance system by editing the node’s Inflows
property. Decay Coefficient
First-order decay coefficient of the pollutant (1/days). Snow Only
YES if pollutant buildup occurs only when there is snow cover, NO otherwise (default is NO). Co-Pollutant
Name of another pollutant whose runoff concentration contributes to the runoff concentration of
the current pollutant. Co-Fraction
Fraction of the co-pollutant’s runoff concentration that contributes to the runoff concentration of
the current pollutant. An example of a co-pollutant relationship would be where the runoff concentration of a particular
heavy metal is some fixed fraction of the runoff concentration of suspended solids. In this case
suspended solids would be declared as the co-pollutant for the heavy metal.

C.17 Snow Pack Editor

The Snow Pack Editor is invoked when a new snow pack object is created or an existing snow
pack is selected for editing. The editor contains a data entry field for the snow pack’s name and
two tabbed pages, one for snow pack parameters and one for snow removal parameters. Snow Pack Parameters Page The Parameters page of the Snow Pack Editor dialog provides snow melt parameters and initial
conditions for snow that accumulates over three different types of areas: the impervious area that
is plowable (i.e., subject to snow removal), the remaining impervious area, and the entire
pervious area. The page contains a data entry grid which has a column for each type of area and
a row for each of the following parameters: Minimum Melt Coefficient
The degree-day snow melt coefficient that occurs on December 21. Units are either in/hr-deg F or
mm/hr-deg C. Maximum Melt Coefficient
The degree-day snow melt coefficient that occurs on June 21. Units are either in/hr-deg F or
mm/hr-deg C. For a short term simulation of less than a week or so it is acceptable to use a
single value for both the minimum and maximum melt coefficients. The minimum and maximum snow melt coefficients are used to estimate a melt coefficient that
varies by day of the year. The latter is used in the following degree-day equation to compute the
melt rate for any particular day: Melt Rate = (Melt Coefficient) * (Air Temperature – Base Temperature). Base Temperature
Temperature at which snow begins to melt (degrees F or C). Fraction Free Water Capacity
The volume of a snow pack’s pore space which must fill with melted snow before liquid runoff
from the pack begins, expressed as a fraction of snow pack depth. Initial Snow Depth
Depth of snow at the start of the simulation (water equivalent depth in inches or millimeters). Initial Free Water
Depth of melted water held within the pack at the start of the simulation (inches or mm). This
number should be at or below the product of the initial snow depth and the fraction free water
capacity. Depth at 100% Cover
The depth of snow beyond which the entire area remains completely covered and is not subject
to any areal depletion effect (inches or mm). Fraction of Impervious Area That is Plowable
The fraction of impervious area that is plowable and therefore is not subject to areal depletion. Snow Removal Parameters Page The Snow Removal page of the Snow Pack Editor describes how snow removal occurs within the
Plowable area of a snow pack. The following parameters govern this process: Depth at which snow removal begins (in or mm)
Depth which must be reached before any snow removal begins. Fraction transferred out of the watershed
The fraction of snow depth that is removed from the system (and does not become runoff). Fraction transferred to the impervious area
The fraction of snow depth that is added to snow accumulation on the pack’s impervious area. Fraction transferred to the pervious area
The fraction of snow depth that is added to snow accumulation on the pack’s pervious area. Fraction converted to immediate melt
The fraction of snow depth that becomes liquid water which runs onto any subcatchment
associated with the snow pack. Fraction moved to another subcatchment
The fraction of snow depth which is added to the snow accumulation on some other
subcatchment. The name of the subcatchment must also be provided. The various removal fractions must add up to 1.0 or less. If less than 1.0, then some remaining
fraction of snow depth will be left on the surface after all of the redistribution options are satisfied.

C.18 Time Pattern Editor

The Time Pattern Editor is invoked when a new time pattern object is created or an existing time
pattern is selected for editing. The editor contains that following data entry fields: Name
Enter the name assigned to the time pattern. Type
Select the type of time pattern being specified. The choices are Monthly, Daily, Hourly and
Weekend Hourly. Description
You can provide an optional comment or description for the time pattern. If more than one line is needed, click the button to launch a multi-line comment editor. Multipliers
Enter a value for each multiplier. The number and meaning of the multipliers changes with the
type of time pattern selected:
 MONTHLY One multiplier for each month of the year.
 DAILY One multiplier for each day of the week.
 HOURLY One multiplier for each hour from 12 midnight to 11 PM.
 WEEKEND Same as for HOURLY except applied to weekend days.
In order to maintain an average dry weather flow or pollutant concentration at its specified
value (as entered on the Inflows Editor), the multipliers for a pattern should average to
1.0.

C.19 Time Series Editor

The Time Series Editor is invoked whenever a new time series object is created or an existing
time series is selected for editing. To use the Time Series Editor:
  1. Enter values for the following standard items:
    Name Name of the time series.
    Description Optional comment or description of what the time series represents.
    Click the button to launch a multi-line comment editor if more than
    one line is needed.
  2. Select whether to use an external file as the source of the data or to enter the data
    directly into the form’s data entry grid.
  3. If the external file option is selected, click the button to locate the file’s name. The
    file’s contents must be formatted in the same manner as the direct data entry option
    discussed below. See the description of Time Series Files in Section
    11.6 Time Series
    Files for details.
  4. For direct data entry, enter values in the data entry grid as follows:
Date Column Optional date (in month/day/year format) of the time series values (only
needed at points in time where a new date occurs).
Time Column If dates are used, enter the military time of day for each time series value
(as hours:minutes or decimal hours). If dates are not used, enter time as
hours since the start of the simulation.
Value Column The time series’ numerical values.
A graphical plot of the data in the grid can be viewed in a separate window by clicking the
View button. Right clicking over the grid will make a popup Edit menu appear. It contains
commands to cut, copy, insert, and paste selected cells in the grid as well as options to
insert or delete a row.
  1. Press OK to accept the time series or Cancel to cancel your edits.
Note that there are two methods for describing the occurrence time of time series data:
 as calendar date/time of day (which requires that at least one date, at the start of the
series, be entered in the Date column)  as elapsed hours since the start of the simulation (where the Date column remains
empty).
For rainfall time series, it is only necessary to enter periods with non-zero rainfall
amounts. SWMM interprets the rainfall value as a constant value lasting over the
recording interval specified for the rain gage which utilizes the time series. For all other
types of time series, SWMM uses interpolation to estimate values at times that fall in
between the recorded values.

C.20 Title/Notes Editor

The Title/Notes editor is invoked when a project’s Title/Notes data category is selected for editing.
As shown below, the editor contains a multi-line edit field where a description of a project can be
entered. It also contains a check box used to indicate whether or not the first line of notes should
be used as a header for printing.

C.21 Transect Editor

The Transect Editor is invoked when a new transect object is created or an existing transect is
selected for editing. It contains the following data entry fields: Name
The name assigned to the transect. Description
An optional comment or description of the transect. Station/Elevation Data Grid
Values of distance from the left side of the channel along with the corresponding elevation of the
channel bottom as one moves across the channel from left to right, looking in the downstream
direction. Up to 1500 data values can be entered. Roughness
Values of Manning’s roughness for the left overbank, right overbank, and main channel portion of
the transect. The overbank roughness values can be zero if no overbank exists. Bank Stations
The distance values appearing in the Station/Elevation grid that mark the end of the left overbank
and the start of the right overbank. Use 0 to denote the absence of an overbank. Modifiers  The Stations modifier is a factor by which the distance between each station will be multiplied
when the transect data is processed by SWMM. Use a value of 0 if no such factor is needed.  The Elevations modifier is a constant value that will be added to each elevation value.  The Meander modifier is the ratio of the length of a meandering main channel to the length of
the overbank area that surrounds it. This modifier is applied to all conduits that use this
particular transect for their cross section. It assumes that the length supplied for these
conduits is that of the longer main channel. SWMM will use the shorter overbank length in its
calculations while increasing the main channel roughness to account for its longer length.
The modifier is ignored if it is left blank or set to 0. Right-clicking over the Data Grid will make a popup Edit menu appear. It contains commands to
cut, copy, insert, and paste selected cells in the grid as well as options to insert or delete a row. Clicking the View button will bring up a window that illustrates the shape of the transect cross
section.

C.22 Treatment Editor

The Treatment Editor is invoked whenever the Treatment property of a node is selected from the
Property Editor. It displays a list of the project’s pollutants with an edit box next to each as shown
below. Enter a valid treatment expression in the box next to each pollutant which receives
treatment. A treatment function can be any well-formed mathematical expression involving:
 the pollutant concentration (use the pollutant name to represent its concentration) – for
non-storage nodes this is the mixture concentration of all flow streams entering the node
while for storage nodes it is the pollutant concentration within the node’s stored volume
 the removals of other pollutants (use R_ prefixed to the pollutant name to represent
removal)
 any of the following process variables:
  • FLOW for flow rate into node (in user-defined flow units)
  • DEPTH for water depth above node invert (ft or m)
  • AREA for node surface area (ft^2 or m^2 )
  • DT for routing time step (sec)
  • HRT for hydraulic residence time (hours)
Any of the following math functions (which are case insensitive) can be used in a treatment
expression:
  • abs(x) for absolute value of x
  • sgn(x) which is +1 for x >= 0 or -1 otherwise
  • step(x) which is 0 for x <= 0 and 1 otherwise
  • sqrt(x) for the square root of x
  • log(x) for logarithm base e of x
  • log10(x) for logarithm base 10 of x
  • exp(x) for e raised to the x power
  • the standard trig functions (sin, cos, tan, and cot)
  • the inverse trig functions (asin, acos, atan, and acot)
  • the hyperbolic trig functions (sinh, cosh, tanh, and coth)
along with the standard operators +, – , *, /, ^ (for exponentiation ) and any level of nested
parentheses.

C.23 Unit Hydrograph Editor

The Unit Hydrograph Editor is invoked whenever a new unit hydrograph object is created or an
existing one is selected for editing. It is used to specify the shape parameters and rain gage for a
group of triangular unit hydrographs. These hydrographs are used to compute rainfall-dependent
infiltration/inflow (RDII) flow at selected nodes of the drainage system. A UH group can contain up
to 12 sets of unit hydrographs (one for each month of the year), and each set can consist of up to
3 individual hydrographs (for short-term, intermediate-term, and long-term responses,
respectively) as well as parameters that describe any initial abstraction losses. The editor
contains the following data entry fields: Name of UH Group
Enter the name assigned to the UH Group. Rain Gage Used
Type in (or select from the dropdown list) the name of the rain gage that supplies rainfall data to
the unit hydrographs in the group. Hydrographs For:
Select a month from the dropdown list box for which hydrograph parameters will be defined.
Select All Months to specify a default set of hydrographs that apply to all months of the year.
Then select specific months that need to have special hydrographs defined. Months listed with a
(*) next to them have had hydrographs assigned to them. Unit Hydrographs
Select this tab to provide the R-T-K shape parameters for each set of unit hydrographs in
selected months of the year. The first row is used to specify parameters for a short-term response
hydrograph (i.e., small value of T), the second for a medium-term response hydrograph, and the
third for a long-term response hydrograph (largest value of T). It is not required that all three
hydrographs be defined and the sum of the three R-values do not have to equal 1. The shape
parameters for each UH consist of:
 R: the fraction of rainfall volume that enters the sewer system
 T: the time from the onset of rainfall to the peak of the UH in hours
 K: the ratio of time to recession of the UH to the time to peak
Initial Abstraction Depth
Select this tab to provide parameters that describe how rainfall will be reduced by any initial
abstraction depth available (i.e., interception and depression storage) before it is processed
through the unit hydrographs defined for a specific month of the year. Different initial abstraction
parameters can be assigned to each of the three unit hydrograph responses. These parameters
are:
 Dmax: the maximum depth of initial abstraction available (in rain depth units)
 Drec: the rate at which any utilized initial abstraction is made available again (in rain
depth units per day)
 Do: the amount of initial abstraction that has already been utilized at the start of the
simulation (in rain depth units).
If a grid cell is left empty its corresponding parameter value is assumed to be 0. Right-clicking
over a data entry grid will make a popup Edit menu appear. It contains commands to cut, copy,
and paste text to or from selected cells in the grid.

APPENDIX D – COMMAND LINE SWMM

D.1 General Instructions EPA SWMM can also be run as a console application from the command line within a DOS
window. In this case the study area data are placed into a text file and results are written to a text
file. The command line for running SWMM in this fashion is:
swmm5 inpfile rptfile outfile
where inpfile is the name of the input file, rptfile is the name of the output report file, and
outfile is the name of an optional binary output file. The latter stores all time series results in a
special binary format that will require a separate post-processor program for viewing. If no binary
output file name is supplied then all time series results will appear in the report file. As written, the
above command assumes that you are working in the directory in which EPA SWMM was
installed or that this directory has been added to the PATH variable in your user profile (or the
autoexec.bat file in older versions of Windows). Otherwise full pathnames for the executable
swmm5.exe and the files on the command line must be used. D.2 Input File Format The input file for command line SWMM has the same format as the project file used by the
Windows version of the program. Figure D-1 illustrates an example SWMM 5 input file. It is
organized in sections, where each section begins with a keyword enclosed in brackets. The
various keywords are listed below.
[TITLE] project title
[OPTIONS] analysis options
[REPORT] output reporting instructions
[FILES] interface file options
[RAINGAGES] rain gage information
[EVAPORATION] evaporation data
[TEMPERATURE] air temperature and snow melt data
[ADJUSTMENTS] monthly adjustments applied to climate variables
[SUBCATCHMENTS] basic subcatchment information
[SUBAREAS] subcatchment impervious/pervious sub-area data
[INFILTRATION] subcatchment infiltration parameters
[LID_CONTROLS] low impact development control information
[LID_USAGE] assignment of LID controls to subcatchments
[AQUIFERS] groundwater aquifer parameters
[GROUNDWATER] subcatchment groundwater parameters
[GWF] groundwater flow expressions
[SNOWPACKS] subcatchment snow pack parameters [JUNCTIONS] junction node information
[OUTFALLS] outfall node information
[DIVIDERS] flow divider node information
[STORAGE] storage node information [CONDUITS] conduit link information
[PUMPS] pump link information
[ORIFICES] orifice link information
[WEIRS] weir link information
[OUTLETS] outlet link information [XSECTIONS] conduit, orifice, and weir cross-section geometry
[TRANSECTS] transect geometry for conduits with irregular cross-sections
[LOSSES] conduit entrance/exit losses and flap valves
[CONTROLS] rules that control pump and regulator operation [POLLUTANTS] pollutant information
[LANDUSES] land use categories
[COVERAGES] assignment of land uses to subcatchments
[LOADINGS] initial pollutant loads on subcatchments
[BUILDUP] buildup functions for pollutants and land uses
[WASHOFF] washoff functions for pollutants and land uses
[TREATMENT] pollutant removal functions at conveyance system nodes [INFLOWS] external hydrograph/pollutograph inflow at nodes
[DWF] baseline dry weather sanitary inflow at nodes
[RDII] rainfall-dependent I/I information at nodes
[HYDROGRAPHS] unit hydrograph data used to construct RDII inflows [CURVES] x-y tabular data referenced in other sections
[TIMESERIES] time series data referenced in other sections
[PATTERNS] periodic multipliers referenced in other sections

[TITLE]

Example SWMM Project [OPTIONS]
FLOW_UNITS CFS
INFILTRATION GREEN_AMPT
FLOW_ROUTING KINWAVE
START_DATE 8/6/2002
START_TIME 10:00
END_TIME 18:00
WET_STEP 00:15:00
DRY_STEP 01:00:00
ROUTING_STEP 00:05:00

[RAINGAGES]

;;Name Format Interval SCF DataSource SourceName
;;=========================================================
GAGE1 INTENSITY 0:15 1.0 TIMESERIES SERIES1 [EVAPORATION]
CONSTANT 0.02 [SUBCATCHMENTS]
;;Name Raingage Outlet Area %Imperv Width Slope
;;====================================================
AREA1 GAGE1 NODE1 2 80.0 800.0 1.0
AREA2 GAGE1 NODE2 2 75.0 50.0 1.0 [SUBAREAS]
;;Subcatch N_Imp N_Perv S_Imp S_Perv %ZER RouteTo
;;=====================================================
AREA1 0.2 0.02 0.02 0.1 20.0 OUTLET
AREA2 0.2 0.02 0.02 0.1 20.0 OUTLET [INFILTRATION]
;;Subcatch Suction Conduct InitDef
;;======================================
AREA1 4.0 1.0 0.34
AREA2 4.0 1.0 0.34 [JUNCTIONS]
;;Name Elev
;;============
NODE1 10.0
NODE2 10.0
NODE3 5.0
NODE4 5.0
NODE6 1.0
NODE7 2.0
Figure D-1 Example SWMM project file

[DIVIDERS]

;;Name Elev Link Type Parameters
;;=======================================
NODE5 3.0 C6 CUTOFF 1.0 [CONDUITS]
;;Name Node1 Node2 Length N Z1 Z2 Q0
;;===========================================================
C1 NODE1 NODE3 800 0.01 0 0 0
C2 NODE2 NODE4 800 0.01 0 0 0
C3 NODE3 NODE5 400 0.01 0 0 0
C4 NODE4 NODE5 400 0.01 0 0 0
C5 NODE5 NODE6 600 0.01 0 0 0
C6 NODE5 NODE7 400 0.01 0 0 0 [XSECTIONS]
;;Link Type G1 G2 G3 G4
;;===================================================
C1 RECT_OPEN 0.5 1 0 0
C2 RECT_OPEN 0.5 1 0 0
C3 CIRCULAR 1.0 0 0 0
C4 RECT_OPEN 1.0 1.0 0 0
C5 PARABOLIC 1.5 2.0 0 0
C6 PARABOLIC 1.5 2.0 0 0 [POLLUTANTS]
;;Name Units Cppt Cgw Cii Kd Snow CoPollut CoFract
;;==========================================================
TSS MG/L 0 0 0 0
Lead UG/L 0 0 0 0 NO TSS 0.20 [LANDUSES]
RESIDENTIAL
UNDEVELOPED [WASHOFF]
;;Landuse Pollutant Type Coeff Expon SweepEff BMPEff
;;===============================================================
RESIDENTIAL TSS EMC 23.4 0 0 0
UNDEVELOPED TSS EMC 12.1 0 0 0 [COVERAGES]
;;Subcatch Landuse Pcnt Landuse Pcnt
;;==================================================
AREA1 RESIDENTIAL 80 UNDEVELOPED 20
AREA2 RESIDENTIAL 55 UNDEVELOPED 45 [TIMESERIES]
;Rainfall time series
SERIES1 0:0 0.1 0:15 1.0 0:30 0.5
SERIES1 0:45 0.1 1:00 0.0 2:00 0.0
Figure D-1 Example SWMM project file (continued from previous page).
The sections can appear in any arbitrary order in the input file, and not all sections must be
present. Each section can contain one or more lines of data. Blank lines may appear anywhere in
the file. A semicolon (;) can be used to indicate that what follows on the line is a comment, not
data. Data items can appear in any column of a line. Observe how in Figure D-1 these features
were used to create a tabular appearance for the data, complete with column headings. Section keywords can appear in mixed lower and upper case, and only the first four characters
(plus the open bracket) are used to distinguish one keyword from another (e.g., [DIVIDERS] and
[Divi] are equivalent). An option is available in the [OPTIONS] section to choose flow units from
among cubic feet per second (CFS), gallons per minute (GPM), million gallons per day (MGD),
cubic meters per second (CMS), liters per second, (LPS), or million liters per day (MLD). If cubic
feet or gallons are chosen for flow units, then US units are used for all other quantities. If cubic
meters or liters are chosen, then metric units apply to all other quantities. The default flow units
are CFS. A detailed description of the data in each section of the input file will now be given. Each section
description begins on a new page. When listing the format of a line of data, mandatory keywords
are shown in boldface while optional items appear in parentheses. A list of keywords separated
by a slash (YES/NO) means that only one of the words should appear in the data line. Section: [TITLE] Purpose: Attaches a descriptive title to the problem being analyzed. Format: Any number of lines may be entered. The first line will be used as a page header in
the output report. Section: [OPTIONS] Purpose: Provides values for various analysis options. Format: FLOW_UNITS CFS / GPM / MGD / CMS / LPS / MLD
INFILTRATION HORTON / MODIFIED_HORTON / GREEN_AMPT
/ MODIFIED_GREEN_AMPT / CURVE_NUMBER
FLOW_ROUTING STEADY / KINWAVE / DYNWAVE LINK_OFFSETS DEPTH / ELEVATION FORCE_MAIN_EQUATION H-W / D-W IGNORE_RAINFALL YES / NO IGNORE_SNOWMELT YES / NO IGNORE_GROUNDWATER YES / NO IGNORE_RDII YES / NO IGNORE_ROUTING YES / NO IGNORE_QUALITY YES / NO ALLOW_PONDING YES / NO
SKIP_STEADY_STATE YES / NO
SYS_FLOW_TOL value
LAT_FLOW_TOL value
START_DATE month/day/year START_TIME hours:minutes END_DATE month/day/year END_TIME hours:minutes REPORT_START_DATE month/day/year REPORT_START_TIME hours:minutes SWEEP_START month/day SWEEP_END month/day DRY_DAYS days
REPORT_STEP hours:minutes:seconds
WET_STEP hours:minutes:seconds
DRY_STEP hours:minutes:seconds ROUTING_STEP seconds
LENGTHENING_STEP seconds
VARIABLE_STEP value
MINIMUM_STEP seconds
INERTIAL_DAMPING NONE / PARTIAL / FULL
NORMAL_FLOW_LIMITED SLOPE / FROUDE / BOTH
MIN_SURFAREA value
MIN_SLOPE value
MAX_TRIALS value
HEAD_TOLERANCE value
THREADS value
TEMPDIR directory
Remarks: FLOW_UNITS makes a choice of flow units. Selecting a US flow unit means that all
other quantities will be expressed in US units, while choosing a metric flow unit will
force all quantities to be expressed in metric units. The default is CFS.
INFILTRATION selects a model for computing infiltration of rainfall into the upper
soil zone of subcatchments. The default model is HORTON.
FLOW_ROUTING determines which method is used to route flows through the
drainage system. STEADY refers to sequential steady state routing (i.e. hydrograph
translation), KINWAVE to kinematic wave routing, DYNWAVE to dynamic wave routing.
The default routing method is KINWAVE.
LINK_OFFSETS determines the convention used to specify the position of a link
offset above the invert of its connecting node. DEPTH indicates that offsets are
expressed as the distance between the node invert and the link while ELEVATION
indicates that the absolute elevation of the offset is used. The default is DEPTH.
FORCE_MAIN_EQUATION establishes whether the Hazen-Williams (H-W) or the
Darcy-Weisbach (D-W) equation will be used to compute friction losses for
pressurized flow in conduits that have been assigned a Circular Force Main cross-
section shape. The default is H-W.
IGNORE_RAINFALL is set to YES if all rainfall data and runoff calculations should be
ignored. In this case SWMM only performs flow and pollutant routing based on user-
supplied direct and dry weather inflows. The default is NO.
IGNORE_SNOWMELT is set to YES if snowmelt calculations should be ignored when a
project file contains snow pack objects. The default is NO.
IGNORE_GROUNDWATER is set to YES if groundwater calculations should be ignored
when a project file contains aquifer objects. The default is NO.
IGNORE_RDII is set to YES if rainfall dependent inflow/infiltration should be ignored
when RDII unit hydrographs and RDII inflows have been supplied to a project file.
The default is NO.
IGNORE_ROUTING is set to YES if only runoff should be computed even if the project
contains drainage system links and nodes. The default is NO. IGNORE_QUALITY is set to YES if pollutant washoff, routing, and treatment should be
ignored in a project that has pollutants defined. The default is NO. ALLOW_PONDING determines whether excess water is allowed to collect atop nodes
and be re-introduced into the system as conditions permit. The default is NO ponding.
In order for ponding to actually occur at a particular node, a non-zero value for its
Ponded Area attribute must be used. SKIP_STEADY_STATE should be set to YES if flow routing computations should be
skipped during steady state periods of a simulation during which the last set of
computed flows will be used. A time step is considered to be in steady state if the
percent difference between total system inflow and total system outflow is below the
SYS_FLOW_TOL and the percent difference between current and previous lateral
inflows are below the LAT_FLOW_TOL. The default for this option is NO. SYS_FLOW_TOL is the maximum percent difference between total system inflow and
total system outflow which can occur in order for the SKIP_STEADY_STATE option to
take effect. The default is 5 percent. LAT_FLOW_TOL is the maximum percent difference between the current and
previous lateral inflow at all nodes in the conveyance system in order for the
SKIP_STEADY_STATE option to take effect. The default is 5 percent. START_DATE is the date when the simulation begins. If not supplied, a date of
1/1/2002 is used. START_TIME is the time of day on the starting date when the simulation begins. The
default is 12 midnight (0:00:00). END_DATE is the date when the simulation is to end. The default is the start date. END_TIME is the time of day on the ending date when the simulation will end. The
default is 24:00:00. REPORT_START_DATE is the date when reporting of results is to begin. The default is
the simulation start date. REPORT_START_TIME is the time of day on the report starting date when reporting is
to begin. The default is the simulation start time of day. SWEEP_START is the day of the year (month/day) when street sweeping operations
begin. The default is 1/1. SWEEP_END is the day of the year (month/day) when street sweeping operations end.
The default is 12/31. DRY_DAYS is the number of days with no rainfall prior to the start of the simulation.
The default is 0. REPORT_STEP is the time interval for reporting of computed results. The default is
0:15:00. WET_STEP is the time step length used to compute runoff from subcatchments
during periods of rainfall or when ponded water still remains on the surface. The
default is 0:05:00. DRY_STEP is the time step length used for runoff computations (consisting essentially
of pollutant buildup) during periods when there is no rainfall and no ponded water.
The default is 1:00:00. ROUTING_STEP is the time step length in seconds used for routing flows and water
quality constituents through the conveyance system. The default is 600 sec (5
minutes) which should be reduced if using dynamic wave routing. Fractional values
(e.g., 2.5) are permissible as are values entered in hours:minutes:seconds format. LENGTHENING_STEP is a time step, in seconds, used to lengthen conduits under
dynamic wave routing, so that they meet the Courant stability criterion under full-flow
conditions (i.e., the travel time of a wave will not be smaller than the specified conduit
lengthening time step). As this value is decreased, fewer conduits will require
lengthening. A value of 0 (the default) means that no conduits will be lengthened. VARIABLE_STEP is a safety factor applied to a variable time step computed for
each time period under dynamic wave flow routing. The variable time step is
computed so as to satisfy the Courant stability criterion for each conduit and yet not
exceed the ROUTING_STEP value. If the safety factor is 0 (the default), then no
variable time step is used. MINIMUM_STEP is the smallest time step allowed when variable time steps are used
for dynamic wave flow routing. The default value is 0.5 seconds. INERTIAL_DAMPING indicates how the inertial terms in the Saint Venant
momentum equation will be handled under dynamic wave flow routing. Choosing
NONE maintains these terms at their full value under all conditions. Selecting
PARTIAL will reduce the terms as flow comes closer to being critical (and ignores
them when flow is supercritical). Choosing FULL will drop the terms altogether. NORMAL_FLOW_LIMITED specifies which condition is checked to determine if flow in
a conduit is supercritical and should thus be limited to the normal flow. Use SLOPE to
check if the water surface slope is greater than the conduit slope, FROUDE to check if the Froude number is greater than 1.0, or BOTH to check both conditions. The default
is BOTH. MIN_SURFAREA is a minimum surface area used at nodes when computing changes
in water depth under dynamic wave routing. If 0 is entered, then the default value of
12.566 ft^2 (i.e., the area of a 4-ft diameter manhole) is used. MIN_SLOPE is the minimum value allowed for a conduit’s slope (%). If zero (the
default) then no minimum is imposed (although SWMM uses a lower limit on
elevation drop of 0.001 ft (0.00035 m) when computing a conduit slope). MAX_TRIALS is the maximum number of trials allowed during a time step to reach
convergence when updating hydraulic heads at the conveyance system’s nodes. The
default value is 8. HEAD_TOLERANCE is the difference in computed head at each node between
successive trials below which the flow solution for the current time step is assumed to
have converged. The default tolerance is 0.005 ft (0.0015 m). THREADS is the number of parallel computing threads to use for dynamic wave flow
routing on machines equipped with multi-core processors. The default is 1. TEMPDIR provides the name of a file directory (or folder) where SWMM writes its
temporary files. If the directory name contains spaces then it should be placed within
double quotes. If no directory is specified, then the temporary files are written to the
current directory that the user is working in. Section: [REPORT] Purpose: Describes the contents of the report file that is produced. Formats: INPUT YES / NO
CONTINUITY YES / NO
FLOWSTATS YES / NO
CONTROLS YES / NO
SUBCATCHMENTS ALL / NONE / <list of subcatchment names>
NODES ALL / NONE / <list of node names>
LINKS ALL / NONE / <list of link names>
LID Name Subcatch Fname
Remarks: INPUT specifies whether or not a summary of the input data should be provided in
the output report. The default is NO.
CONTINUITY specifies whether continuity checks should be reported or not. The
default is YES.
FLOWSTATS specifies whether summary flow statistics should be reported or not. The
default is YES.
CONTROLS specifies whether all control actions taken during a simulation should be
listed or not. The default is NO.
SUBCATCHMENTS gives a list of subcatchments whose results are to be reported. The
default is NONE.
NODES gives a list of nodes whose results are to be reported. The default is NONE.
LINKS gives a list of links whose results are to be reported. The default is NONE.
LID specifies that the LID control Name in subcatchment Subcatch should have a
detailed performance report for it written to file Fname.
The SUBCATCHMENTS, NODES, LINKS, and LID lines can be repeated multiple
times.
Section: [FILES] Purpose: Identifies optional interface files used or saved by a run. Formats: USE / SAVE RAINFALL Fname
USE / SAVE RUNOFF Fname
USE / SAVE HOTSTART Fname
USE / SAVE RDII Fname
USE INFLOWS Fname
SAVE OUTFLOWS Fname
Remarks: Fname is the name of an interface file. Refer to Section 11.7 Interface Files for a description of interface files. Rainfall, Runoff, and
RDII files can either be used or saved in a run, but not both. A run can both use and save a Hot
Start file (with different names). Section: [RAINGAGES] Purpose: Identifies each rain gage that provides rainfall data for the study area. Formats: Name Form Intvl SCF TIMESERIES Tseries
Name Form Intvl SCF FILE Fname Sta Units
Remarks: Name name assigned to rain gage.
Form form of recorded rainfall, either INTENSITY, VOLUME or CUMULATIVE.
Intvl time interval between gage readings in decimal hours or hours:minutes
format (e.g., 0:15 for 15-minute readings).
SCF snow catch deficiency correction factor (use 1.0 for no adjustment).
Tseries name of time series in [TIMESERIES] section with rainfall data.
Fname name of external file with rainfall data. Rainfall files are discussed in
Section 11.3 Rainfall Files.
Sta name of recording station used in the rain file.
Units rain depth units used in the rain file, either IN (inches) or MM
(millimeters).
Section: [EVAPORATION] Purpose: Specifies how daily evaporation rates vary with time for the study area. Formats: CONSTANT evap
MONTHLY e1 e2 e3 e4 e5 e6 e7 e8 e9 e10 e11 e12
TIMESERIES Tseries
TEMPERATURE
FILE (p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12)
RECOVERY patternID
DRY_ONLY NO / YES
Remarks: evap constant evaporation rate (in/day or mm/day). e1 evaporation rate in January (in/day or mm/day).
… e12 evaporation rate in December (in/day or mm/day).
Tseries name of time series in [TIMESERIES] section with evaporation data.
p1 pan coefficient for January.
...
p12 pan coefficient for December.
patID name of a monthly time pattern.
Use only one of the above formats (CONSTANT, MONTHLY, TIMESERIES,
TEMPERATURE, or FILE). If no [EVAPORATION] section appears, then evaporation is
as sumed to be 0.
TEMPERATURE indicates that evaporation rates will be computed from the daily air
temperatures contained in an external climate file whose name is provided in the
[TEMPERATURE] section (see below). This method also uses the site’s latitude, which
can also be specified in the [TEMPERATURE] section.
FILE indicates that evaporation data will be read directly from the same external
climate file used for air temperatures as specified in the [TEMPERATURE] section
(see below).
RECOVERY identifies a n optional monthly time pattern of multipliers used to modify
infiltration recovery rates during dry periods. For example, if the normal infiltration
recovery rate was 1% during a specific time period and a pattern factor of 0.8 applied
to this period, then the actual recovery rate would be 0.8%.
DRY_ONLY determines if evaporation only occurs during periods with no precipitation.
The default is NO.
Section: [TEMPERATURE] Purpose: Specifies daily air temperatures, monthly wind speed, and various snowmelt
parameters for the study area. Required only when snowmelt is being modeled or
when evaporation rates are computed from daily temperatures or are read from an
external climate file. Formats: TIMESERIES Tseries
FILE Fname (Start)
WINDSPEED MONTHLY s1 s2 s3 s4 s5 s6 s7 s8 s9 s10 s11 s12
WINDSPEED FILE
SNOWMELT Stemp ATIwt RNM Elev Lat DTLong
ADC IMPERVIOUS f.0 f.1 f.2 f.3 f.4 f.5 f.6 f.7 f.8 f.9
ADC PERVIOUS f.0 f.1 f.2 f.3 f.4 f.5 f.6 f.7 f.8 f.9
Remarks: Tseries name of time series in [TIMESERIES] section with temperature data.
Fname name of external Climate file with temperature data.
Start date to begin reading from the file in month/day/year format (default is
the beginning of the file).
s1 average wind speed in January (mph or km/hr).
...
s12 average wind speed in December (mph or km/hr).
Stemp air temperature at which precipitation falls as snow (deg F or C).
ATIwt antecedent temperature index weight (default is 0.5).
RNM negative melt ratio (default is 0.6).
Elev average elevation of study area above mean sea level (ft or m) (default is
0).
Lat latitude of the study area in degrees North (default is 50).
DTLong correction, in minutes of time, between true solar time and the standard
clock time (default is 0).
f.0 fraction of area covered by snow when ratio of snow depth to depth at
100% cover is 0
....
f.9 fraction of area covered by snow when ratio of snow depth to depth at
100% cover is 0.9.
Use the TIMESERIES line to read air temperature from a time series or the FILE line
to read it from an external Climate file. Climate files are discussed in Section 11.4
Climate Files. If neither format is used, then air temperature remains constant at
70 degrees F.
Wind speed can be specified either by monthly average values or by the same
Climate file used for air temperature. If neither option appears, then wind speed is
assumed to be 0. Separate Areal Depletion Curves (ADC) can be defined for impervious and pervious
sub-areas. The ADC parameters will default to 1.0 (meaning no depletion) if no data
are supplied for a particular type of sub-area. Section: [ADJUSTMENTS] Purpose: Specifies optional monthly adjustments to be made to temperature, evaporation rate,
rainfall intensity and hydraulic conductivity in each time period of a simulation. Format: TEMPERATURE t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12
EVAPORATION e1 e2 e3 e4 e5 e6 e7 e8 e9 e10 e11 e12
RAINFALL r1 r2 r3 r4 r5 r6 r7 r8 r9 r10 r11 r12
CONDUCTIVITY c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12 Remarks: t1..t12 adjustments to temperature in January, February, etc., as plus or minus
degrees F (degrees C).
e1..e12 adjustments to evaporation rate in January, February, etc., as plus or
minus in/day (mm/day).
r1..r 12 multipliers applied to precipitation rate in January, February, etc.
c1..c12 multipliers applied to soil hydraulic conductivity in January, February, etc.
used in either Horton or Green-Ampt infiltration. The same adjustment is applied for each time period within a given month and is repeated for that
month in each subsequent year being simulated. Section: [SUBCATCHMENTS] Purpose: Identifies each subcatchment within the study area. Subcatchments are land area
units which generate runoff from rainfall. Format: Name Rgage OutID Area %Imperv Width Slope Clength (Spack) Remarks: Name name assigned to subcatchment.
Rgage name of rain gage in [RAINGAGES] section assigned to subcatchment.
OutID name of node or subcatchment that receives runoff from subcatchment.
Area area of subcatchment (acres or hectares).
%Imperv percent imperviousness of subcatchment.
Width characteristic width of subcatchment (ft or meters).
Slope subcatchment slope (percent).
Clength total curb length (any length units). Use 0 if not applicable.
Spack optional name of snow pack object (from [SNOWPACKS] section) that
characterizes snow accumulation and melting over the subcatchment.
Section: [SUBAREAS] Purpose: Supplies information about pervious and impervious areas for each subcatchment.
Each subcatchment can consist of a pervious sub-area, an impervious sub-area with
depression storage, and an impervious sub-area without depression storage. Format: Subcat Nimp Nperv Simp Sperv %Zero RouteTo (%Routed) Remarks: Subcat subcatchment name.
Nimp Manning's n for overland flow over the impervious sub-area.
Nperv Manning's n for overland flow over the pervious sub-area.
Simp depression storage for impervious sub-area (inches or mm).
Sperv depression storage for pervious sub-area (inches or mm).
%Zero percent of impervious area with no depression storage.
RouteTo IMPERVIOUS if pervious area runoff runs onto impervious area,
PERVIOUS if impervious runoff runs onto pervious area, or OUTLET if
both areas drain to the subcatchment's outlet (default = OUTLET).
%Routed percent of runoff routed from one type of area to another (default = 100).
Section: [INFILTRATION] Purpose: Supplies infiltration parameters for each subcatchment. Rainfall lost to infiltration only
occurs over the pervious sub-area of a subcatchment. Formats: Subcat MaxRate MinRate Decay DryTime MaxInf
Subcat Psi Ksat IMD
Subcat CurveNo Ksat DryTime
Remarks: Subcat subcatchment name.
For Horton and Modified Horton Infiltration:
MaxRate maximum infiltration rate on Horton curve (in/hr or mm/hr).
MinRate minimum infiltration rate on Horton curve (in/hr or mm/hr).
Decay decay rate constant of Horton curve (1/hr).
DryTime time it takes for fully saturated soil to dry (days).
MaxInf maximum infiltration volume possible (0 if not applicable) (in or mm).
For Green-Ampt and Modified Green-Ampt Infiltration:
Psi soil capillary suction (in or mm).
Ksat soil saturated hydraulic conductivity (in/hr or mm/hr).
IMD initial soil moisture deficit (volume of voids / total volume).
For Curve-Number Infiltration:
CurveNo SCS Curve Number.
Ksat soil saturated hydraulic conductivity (in/hr or mm/hr)
(This property has been deprecated and is no longer used.)
DryTime time it takes for fully saturated soil to dry (days).
Section: [LID_CONTROLS] Purpose: Defines scale-independent LID controls that can be deployed within subcatchments. Formats: Name Type followed by one or more of the following lines depending on Type:
Name SURFACE StorHt VegFrac Rough Slope Xslope
Name SOIL Thick Por FC WP Ksat Kcoeff Suct
Name PAVEMENT Thick Vratio FracImp Perm Vclog
Name STORAGE Height Vratio S eepage Vclog
Name DRAIN Coeff E xpon Offset Delay
Name DRAINMAT Thick Vratio Rough
Remarks: Name name assigned to LID process.
Type BC for bio-retention cell; RG for rain garden; GR for green roof; IT for
infiltration trench; PP for permeable pavement; RB for rain barrel; RD for
rooftop disconnection; VS for vegetative swale.
For LIDs with Surface Layers:
StorHt when confining walls or berms are present this is the maximum depth to
which water can pond above the surface of the unit before overflow
occurs (in inches or mm). For LIDs that experience overland flow it is the
height of any surface depression storage. For swales, it is the height of
its trapezoidal cross section.
VegFrac fraction of the surface storage volume that is filled with vegetation.
Rough Manning's n for overland flow over surface soil cover, pavement, roof
surface or a vegetative swale. Use 0 for other types of LIDs.
Slope s lope of a roof surface, pavement surface or vegetative swale (percent).
Use 0 for other types of LIDs.
Xslope slope (run over rise) of the side walls of a vegetative swale's cross
section. Use 0 for other types of LIDs.
If either Rough or Slope values are 0 then any ponded water that exceeds the
surface storage depth is assumed to completely overflow the LID control within a
single time step.
For LIDs with Pavement Layers:
Thick thickness of the pavement layer (inches or mm).
Vratio void ratio (volume of void space relative to the volume of solids in the
pavement for continuous systems or for the fill material used in modular
systems). Note that porosity = void ratio / (1 + void ratio).
FracImp ratio of impervious paver material to total area for modular systems; 0 for
continuous porous pavement systems. Perm permeability of the concrete or asphalt used in continuous systems or
hydraulic conductivity of the fill material (gravel or sand) used in modular
systems (in/hr or mm/hr). Vclog number of pavement layer void volumes of runoff treated it takes to
completely clog the pavement. Use a value of 0 to ignore clogging. For LIDs with Soil Layers: Thick thickness of the soil layer (inches or mm). Por soil porosity ( volume of pore space relative to total volume). FC soil field capacity (volume of pore water relative to total volume after the
soil has been allowed to drain fully). WP soil wilting point (volume of pore water relative to total volume for a well
dried soil where only bound water remains). Ksat soil’s saturated hydraulic conductivity (in/hr or mm/hr). Kcoeff slope of the curve of log(conductivity) versus soil moisture content
(dimensionless). Suct soil capillary suction (in or mm). For LIDs with Storage Layers: Height thickness of the storage layer or height of a rain barrel (inches or mm). Vratio void ratio (volume of void space relative to the volume of solids in the
layer). Note that porosity = void ratio / (1 + void ratio). Seepage the rate at which water seeps from the layer into the underlying native
soil when first constructed (in/hr or mm/hr). If there is an impermeable
floor or liner below the layer then use a value of 0. Vclog number of storage layer void volumes of runoff treated it takes to
completely clog the layer. Use a value of 0 to ignore clogging. Values for Vratio, Seepage, and Vclog are ignored for rain barrels. For LIDs with Drain Systems: Coeff coefficient C that determines the rate of flow through the drain as a
function of height of stored water above the drain bottom. For Rooftop
Disconnection it is the maximum flow rate (in inches/hour or mm/hour)
that the roof’s gutters and downspouts can handle before overflowing. Expon exponent n that determines the rate of flow through the drain as a
function of height of stored water above the drain outlet. Offset height of the drain line above the bottom of the storage layer or rain
barrel (inches or mm).
Delay number of dry weather hours that must elapse before the drain line in a
rain barrel is opened (the line is assumed to be closed once rainfall
begins). A value of 0 signifies that the barrel's drain line is always open
and drains continuously. This parameter is ignored for other types of
LIDs.
For Green Roof LIDs with Drainage Mats:
Thick thickness of the drainage mat (inches or mm).
Vratio ratio of void volume to total volume in the mat.
Rough Manning's n constant used to compute the horizontal flow rate of drained
water through the mat.
The following table shows which layers are required (x) or are optional (o) for each type of LID
process:
LID Type Surface Pavement Soil Storage Drain Drain Mat
Bio-Retention Cell x x x o
Rain Garden x x
Green Roof x x x
Infiltration Trench x x o
Permeable
Pavement
x x o x o
Rain Barrel x x^
Rooftop
Disconnection
x x
Vegetative Swale x
The equation used to compute flow rate out of the underdrain per unit area of the LID (in in/hr or mm/hr) is (^) −= d)Hh(Cq n where q is outflow, h is height of stored water (inches or mm) and Hd
is the drain offset height. Note that the units of C depend on the unit system being used as well
as the value assigned to n.
The actual dimensions of an LID control are provided in the [LID_USAGE] section when it is
placed in a particular subcatchment.
Examples: ;A street planter with no drain
Planter BC
Planter SURFACE 6 0.3 0 0 0
Planter SOIL 24 0.5 0.1 0.05 1.2 2.4
Planter STORAGE 12 0.5 0.5 0 ;A green roof with impermeable bottom
GR1 BC
GR1 SURFACE 3 0 0 0 0
GR1 SOIL 3 0.5 0.1 0.05 1.2 2.4
GR1 STORAGE 3 0.5 0 0
GR1 DRAIN 5 0.5 0 0 ;A rain barrel that drains 6 hours after rainfall ends
RB12 RB
RB12 STORAGE 36 0 0 0
RB12 DRAIN 10 0.5 0 6 ;A grass swale 24 in. high with 5:1 side slope
Swale VS
Swale SURFACE 24 0 0.2 3 5 Section: [LID_USAGE] Purpose: Deploys LID controls within specific subcatchment areas. Format: Subcat LID Number Area Width InitSat FromImp ToPerv
(RptFile DrainTo)
Remarks: Subcat name of the subcatchment using the LID process.
LID name of an LID process defined in the [LID_CONTROLS] section.
Number number of replicate LID units deployed.
Area area of each replicate unit (ft^2 or m^2 ).
Width width of the outflow face of each identical LID unit (in ft or m). This
parameter applies to roofs, pavement, trenches, and swales that use
overland flow to convey surface runoff off of the unit. It can be set to 0 for
other LID processes, such as bio-retention cells, rain gardens, and rain
barrels that simply spill any excess captured runoff over their berms.
InitSat for bio-retention cells, rain gardens, and green roofs this is the degree to
which the unit's soil is initially filled with water (0 % saturation
corresponds to the wilting point moisture content, 100 % saturation has
the moisture content equal to the porosity). The storage zone beneath
the soil zone of the cell is assumed to be completely dry. For other types
of LIDs it corresponds to the degree to which their storage zone is
initially filled with water
FromImp percent of the impervious portion of the subcatchment’s non-LID area
whose runoff is treated by the LID practice. (E.g., if rain barrels are used
to capture roof runoff and roofs represent 60% of the impervious area,
then the impervious area treated is 60%). If the LID unit treats only direct
rainfall, such as with a green roof, then this value should be 0. If the LID
takes up the entire subcatchment then this field is ignored.
ToPerv a value of 1 indicates that the surface and drain flow from the LID unit
should be routed back onto the pervious area of the subcatchment that
contains it. This would be a common choice to make for rain barrels,
rooftop disconnection, and possibly green roofs. The default value is 0.
RptFile optional name of a file to which detailed time series results for the LID
will be written. Enclose the name in double quotes if it contains spaces
and include the full path if it is different than the SWMM input file path.
Use ‘*’ if not applicable and an entry for DrainTo follows
DrainTo optional name of subcatchment or node that receives flow from the unit’s
drain line, if different from the outlet of the subcatchment that the LID is
placed in.
If ToPerv is set to 1 and DrainTo set to some other outlet, then only the excess
surface flow from the LID unit will be routed back to the subcatchment’s pervious
area while the underdrain flow will be sent to DrainTo.
More than one type of LID process can be deployed within a subcatchment as long
as their total area does not exceed that of the subcatchment and the total percent
impervious area treated does not exceed 100.
Examples: ;34 rain barrels of 12 sq ft each are placed in
;subcatchment S1. They are initially empty and treat 17%
;of the runoff from the subcatchment’s impervious area.
;The outflow from the barrels is returned to the
;subcatchment’s pervious area.
S1 RB14 34 12 0 0 17 1 ;Subcatchment S2 consists entirely of a single vegetative
;swale 200 ft long by 50 ft wide.
S2 Swale 1 10000 50 0 0 0 “swale.rpt” Section: [AQUIFERS] Purpose: Supplies parameters for each unconfined groundwater aquifer in the study area.
Aquifers consist of two zones – a lower saturated zone and an upper unsaturated
zone with a moving boundary between the two. Formats: Name Por WP FC Ks Kslp Tslp ETu ETs Seep Ebot Egw Umc (Epat) Remarks: Name name assigned to aquifer.
Por soil porosity (volumetric fraction).
WP soil wilting point (volumetric fraction).
FC soil field capacity (volumetric fraction).
Ks saturated hydraulic conductivity (in/hr or mm/hr).
Kslp slope of the logarithm of hydraulic conductivity versus moisture deficit (i.e.,
porosity minus moisture content) curve (in/hr or mm/hr).
Ts lp slope of soil tension versus moisture content curve (inches or mm).
ETu fraction of total evaporation available for evapotranspiration in the upper
unsaturated zone.
ETs maximum depth into the lower saturated zone over which evapotranspiration
can occur (ft or m).
Seep seepage rate from saturated zone to deep groundwater when water table is
at ground surface (in/hr or mm/hr).
Ebot elevation of the bottom of the aquifer (ft or m).
Egw groundwater table elevation at start of simulation (ft or m).
Umc unsaturated zone moisture content at start of simulation (volumetric fraction).
Epat name of optional monthly time pattern used to adjust the upper zone
evaporation fraction for different months of the year.
Local values for Ebot, Egw, and Umc can be assigned to specific subcatchments in
the [GROUNDWATER] section described below.
Section: [GROUNDWATER] Purpose: Supplies parameters that determine the rate of groundwater flow between the aquifer
underneath a subcatchment and a node of the conveyance system. Format:
Subcat Aquifer Node Esurf A1 B1 A2 B2 A3 Dsw (Egwt Ebot Egw Umc) Remarks: Subcat subcatchment name.
Aquifer name of groundwater aquifer underneath the subcatchment.
Node name of node in conveyance system exchanging groundwater with
aquifer.
Esurf surface elevation of subcatchment (ft or m).
A1 groundwater flow coefficient (see below).
B1 groundwater flow exponent (see below).
A2 surface water flow coefficient (see below).
B2 surface water flow exponent (see below).
A3 surface water – groundwater interaction coefficient (see below).
Dsw fixed depth of surface water at receiving node (ft or m) (set to zero if
surface water depth will vary as computed by flow routing).
Egwt threshold groundwater table elevation which must be reached before any
flow occurs (ft or m). Leave blank (or enter *) to use the elevation of the
receiving node's invert.
The following optional parameters can be used to override the values supplied for the
subcatchment’s aquifer.
Ebot elevation of the bottom of the aquifer (ft or m).
Egw groundwater table elevation at the start of the simulation (ft or m).
Umc unsaturated zone moisture content at start of simulation (volumetric fraction).
The flow coefficients are used in the following equation that determines the lateral groundwater
flow rate based on groundwater and surface water elevations: QL = A1 (Hgw – Hcb) B1 – A2 (Hsw – Hcb) B2 + A3 Hgw Hsw where:
QL = lateral groundwater flow (cfs per acre or cms per hectare),
Hgw = height of saturated zone above bottom of aquifer (ft or m),
Hsw = height of surface water at receiving node above aquifer bottom (ft or m),
Hcb = height of channel bottom above aquifer bottom (ft or m). Section: [GWF] Purpose: Defines custom groundwater flow equations for specific subcatchments. Format: Subcat LATERAL/DEEP Expr Remarks: Subcat subcatchment name. Expr math formula expressing the rate of groundwater flow (in cfs per acre or
cms per hectare for lateral flow or in/hr or mm/hr for deep flow) as a
function of the following variables:
Hgw (for height of the groundwater table)
Hsw (for height of the surface water)
Hcb (for height of the channel bottom)
Hgs (for height of ground surface)
where all heights are relative to the aquifer bottom and have
units of either feet or meters;
Ks (for saturated hydraulic conductivity in in/hr or mm/hr)
K (for unsaturated hydraulic conductivity in in/hr or mm/hr)
Theta (for moisture content of unsaturated zone)
Phi (for aquifer soil porosity)
Fi (for infiltration rate from the ground surface in in/hr or mm/hr)
Fu (for percolation rate from the upper unsaturated zone in in/hr or
mm/hr)
A (for subcatchment area in acres or hectares)
Use LATERAL to designate an expression for lateral groundwater flow (to a node of
the conveyance network) and DEEP for vertical loss to deep groundwater.
See the [TREATMENT] section for a list of built-in math functions that can be used in
Expr. In particular, the STEP(x) function is 1 when x > 0 and is 0 otherwise.
Examples: ;Two-stage linear reservoir for lateral flow
Subcatch1 LATERAL 0.001Hgw + 0.05(Hgw–5)*STEP(Hgw–5)
;Constant seepage rate to deep aquifer
Subactch1 DEEP 0.002
Section: [SNOWPACKS] Purpose: Specifies parameters that govern how snowfall accumulates and melts on the
plowable, impervious and pervious surfaces of subcatchments. Formats: Name PLOWABLE Cmin Cmax Tbase FWF SD0 FW0 SNN0
Name IMPERVIOUS Cmin Cmax Tbase FWF SD0 FW0 SD100
Name PERVIOUS Cmin Cmax Tbase FWF SD0 FW0 SD100
Name REMOVAL Dplow Fout Fimp Fperv Fimelt (Fsub Scatch)
Remarks: Name name assigned to snowpack parameter set.
Cmin minimum melt coefficient (in/hr-deg F or mm/hr-deg C).
Cmax maximum melt coefficient (in/hr-deg F or mm/hr-deg C).
Tbase snow melt base temperature (deg F or deg C).
FWF ratio of free water holding capacity to snow depth (fraction).
SD0 initial snow depth (in or mm water equivalent).
FW0 initial free water in pack (in or mm).
SNN0 fraction of impervious area that can be plowed.
SD100 snow depth above which there is 100% cover (in or mm water
equivalent).
Dplow depth of snow on plowable areas at which snow removal begins (in or
mm).
Fout fraction of snow on plowable area transferred out of watershed.
Fimp fraction of snow on plowable area transferred to impervious area by
plowing.
Fperv fraction of snow on plowable area transferred to pervious area by
plowing.
Fimelt fraction of snow on plowable area converted into immediate melt.
Fsub fraction of snow on plowable area transferred to pervious area in
another subcatchment.
Scatch name of subcatchment receiving the Fsub fraction of transferred snow.
Use one set of PLOWABLE, IMPERVIOUS, and PERVIOUS lines for each snow pack
parameter set created. Snow pack parameter sets are associated with specific
subcatchments in the [SUBCATCHMENTS] section. Multiple subcatchments can share
the same set of snow pack parameters.
The PLOWABLE line contains parameters for the impervious area of a subcatchment
that is subject to snow removal by plowing but not to areal depletion. This area is the
fraction SNN0 of the total impervious area. The IMPERVIOUS line contains parameter
values for the remaining impervious area and the PERVIOUS line does the same for
the entire pervious area. Both of the latter two areas are subject to areal depletion. The REMOVAL line describes how snow removed from the plowable area is
transferred onto other areas. The various transfer fractions should sum to no more
than 1.0. If the line is omitted then no snow removal takes place. Section: [JUNCTIONS] Purpose: Identifies each junction node of the drainage system. Junctions are points in space
where channels and pipes connect together. For sewer systems they can be either
connection fittings or manholes. Format: Name Elev (Ymax Y0 Ysur Apond) Remarks: Name name assigned to junction node.
Elev elevation of junction invert (ft or m).
Ymax depth from ground to invert elevation (ft or m) (default is 0).
Y0 water depth at start of simulation (ft or m) (default is 0).
Ysur maximum additional head above ground elevation that manhole junction
can sustain under surcharge conditions (ft or m) (default is 0).
Apond area subjected to surface ponding once water depth exceeds Ymax (ft^2 or
m^2 ) (default is 0).
If Ymax is 0 then SWMM sets the maximum depth equal to the distance from the
invert to the top of the highest connecting link.
If the junction is part of a force main section of the system then set Ysur to the
maximum pressure that the system can sustain.
Surface ponding can only occur when Apond is non-zero and the ALLOW_PONDING
analysis option is turned on.
Section: [OUTFALLS] Purpose: Identifies each outfall node (i.e., final downstream boundary) of the drainage system
and the corresponding water stage elevation. Only one link can be incident on an
outfall node. Formats: Name Elev FREE (Gated) (RouteTo)
Name Elev NORMAL (Gated) (RouteTo)
Name Elev FIXED Stage (Gated) (RouteTo)
Name Elev TIDAL Tcurve (Gated) (RouteTo)
Name Elev TIMESERIES Tseries (Gated) (RouteTo)
Remarks: Name name assigned to outfall node.
Elev invert elevation (ft or m).
Stage elevation of fixed stage outfall (ft or m).
Tcurve name of curve in [CURVES] section containing tidal height (i.e., outfall
stage) v. hour of day over a complete tidal cycle.
Tseries name of time series in [TIMESERIES] section that describes how outfall
stage varies with time.
Gated YES or NO depending on whether a flap gate is present that prevents
reverse flow. The default is NO.
RouteTo optional name of a subcatchment that receives the outfall's discharge.
The default is not to route the outfall’s discharge.
Section: [DIVIDERS] Purpose: Identifies each flow divider node of the drainage system. Flow dividers are junctions
with exactly two outflow conduits where the total outflow is divided between the two in
a prescribed manner. Formats: Name Elev DivLink OVERFLOW (Ymax Y0 Ysur Apond)
Name Elev DivLink CUTOFF Qmin (Ymax Y0 Ysur Apond)
Name Elev DivLink TABULAR Dcurve (Ymax Y0 Ysur Apond)
Name Elev DivLink WEIR Qmin Ht Cd (Ymax Y0 Ysur Apond)
Remarks: Name name assigned to divider node.
Elev invert elevation (ft or m).
DivLink name of link to which flow is diverted.
Qmin flow at which diversion begins for either a CUTOFF or WEIR divider (flow
units).
Dcurve name of curve for TABULAR divider that relates diverted flow to total flow.
Ht height of WEIR divider (ft or m).
Cd discharge coefficient for WEIR divider.
Ymax depth from ground to invert elevation (ft or m) (default is 0).
Y0 water depth at start of simulation (ft or m) (default is 0).
Ysur maximum additional head above ground elevation that node can sustain
under surcharge conditions (ft or m) (default is 0).
Apond area subjected to surface ponding once water depth exceeds Ymax (ft^2 or
m^2 ) (default is 0).
If Ymax is 0 then SWMM sets the maximum depth equal to the distance from the
invert to the top of the highest connecting link.
Surface ponding can only occur when Apond is non-zero and the ALLOW_PONDING
analysis option is turned on.
Divider nodes are only active under the Steady Flow or Kinematic Wave analysis
options. For Dynamic Wave flow routing they behave the same as Junction nodes.
Section: [STORAGE] Purpose: Identifies each storage node of the drainage system. Storage nodes can have any
shape as specified by a surface area versus water depth relation. Formats: Name Elev Ymax Y0 TABULAR Acurve (Apond Fevap Psi Ksat IMD) Name Elev Ymax Y0 FUNCTIONAL A1 A2 A0 (Apond Fevap Psi Ksat IMD) Remarks: Name name assigned to storage node.
Elev invert elevation (ft or m).
Ymax maximum water depth possible (ft or m).
Y0 water depth at the start of the simulation (ft or m).
Acurve name of curve in [CURVES] section with surface area (ft^2 or m^2 ) as a
function of depth (ft or m) for TABULAR geometry.
A1 coefficient of FUNCTIONAL relation between surface area and depth.
A2 exponent of FUNCTIONAL relation between surface area and depth.
A0 constant of FUNCTIONAL relation between surface area and depth.
Apond this parameter has been deprecated – use 0.
Fevap fraction of potential evaporation from surface realized (default is 0).
Psi soil suction head (inches or mm).
Ksat soil saturated hydraulic conductivity (in/hr or mm/hr).
IMD soil initial moisture deficit (fraction).
A1, A2, and A0 are used in the following expression that relates surface area (ft^2 or
m^2 ) to water depth (ft or m) for a storage unit with FUNCTIONAL geometry:
퐴퐴퐴퐴퐴퐴퐴퐴=퐴퐴0 +퐴퐴 1 퐷퐷퐴퐴퐷퐷퐷퐷ℎ퐴퐴2
For TABULAR geometry, the surface area curve will be extrapolated outwards to
meet the unit's maximum depth if need be.
The parameters Psi, Ksat, and IMD need only be supplied if seepage loss through
the soil at the bottom and sloped sides of the storage unit should be considered.
They are the same Green-Ampt infiltration parameters described in the
[INFILTRATION] section. If Ksat is zero then no seepage occurs while if IMD is
zero then seepage occurs at a constant rate equal to Ksat. Otherwise seepage rate
will vary with storage depth.
Section: [CONDUITS] Purpose: Identifies each conduit link of the drainage system. Conduits are pipes or channels
that convey water from one node to another. Format: Name Node1 Node2 Length N Z1 Z2 (Q0 Qmax) Remarks: Name name assigned to conduit link.
Node1 name of upstream node.
Node2 name of downstream node.
Length conduit length (ft or m).
N value of n (i.e., roughness parameter) in Manning’s equation.
Z1 offset of upstream end of conduit invert above the invert elevation of its
upstream node (ft or m).
Z2 offset of downstream end of conduit invert above the invert elevation of
its downstream node (ft or m).
Q0 flow in conduit at start of simulation (flow units) (default is 0).
Qmax maximum flow allowed in the conduit (flow units) (default is no limit).
The figure below illustrates the meaning of the Z1 and Z2 parameters.

Z1

Z2

These offsets are expressed as a relative distance above the node invert if the
LINK_OFFSETS option is set to DEPTH (the default) or as an absolute elevation if it is
set to ELEVATION.
Section: [PUMPS] Purpose: Identifies each pump link of the drainage system. Format: Name Node1 Node2 Pcurve (Status Startup Shutoff) Remarks: Name name assigned to pump link.
Node1 name of node on inlet side of pump.
Node2 name of node on outlet side of pump.
Pcurve name of pump curve listed in the [CURVES] section of the input.
Status status at start of simulation (either ON or OFF; default is ON).
Startup depth at inlet node when pump turns on (ft or m) (default is 0).
Shutoff depth at inlet node when pump shuts off (ft or m) (default is 0).
See Section 3.2 for a description of the different types of pumps available.
Section: [ORIFICES] Purpose: Identifies each orifice link of the drainage system. An orifice link serves to limit the
flow exiting a node and is often used to model flow diversions and storage node
outlets. Format: Name Node1 Node2 Type Offset Cd (Gated Orate) Remarks: Name name assigned to orifice link.
Node1 name of node on inlet end of orifice.
Node2 name of node on outlet end of orifice.
Type orientation of orifice: either SIDE or BOTTOM.
Offset amount that a Side Orifice’s bottom or the position of a Bottom Orifice is
offset above the invert of inlet node (ft or m, expressed as either a depth
or as an elevation, depending on the LINK_OFFSETS option setting).
Cd discharge coefficient (unitless).
Flap YES if flap gate present to prevent reverse flow, NO if not (default is NO).
Orate time in decimal hours to open a fully closed orifice (or close a fully open
one). Use 0 if the orifice can open/close instantaneously.
The geometry of an orifice’s opening must be described in the [XSECTIONS] section.
The only allowable shapes are CIRCULAR and RECT_CLOSED (closed rectangular).
Offset
Orifice
Regulator
Structure
Section: [WEIRS] Purpose: Identifies each weir link of the drainage system. Weirs are used to model flow
diversions and storage node outlets. Format:
Name Node1 Node2 Type CrestHt Cd (Gated EC Cd2 Sur (Width Surface)) Remarks: Name name assigned to weir link.
Node1 name of node on inlet side of wier.
Node2 name of node on outlet side of weir.
Type TRANSVERSE, SIDEFLOW, V-NOTCH, TRAPEZOIDAL or ROADWAY.
CrestHt amount that the weir’s crest is offset above the invert of inlet node (ft or
m, expressed as either a depth or as an elevation, depending on the
LINK_OFFSETS option setting).
Cd weir discharge coefficient (for CFS if using US flow units or CMS if using
metric flow units).
Gated YES if flap gate present to prevent reverse flow, NO if not (default is NO).
EC number of end contractions for TRANSVERSE or TRAPEZOIDAL weir
(default is 0).
Cd2 discharge coefficient for triangular ends of a TRAPEZOIDAL weir (for
CFS if using US flow units or CMS if using metric flow units) (default is
value of Cd).
Sur YES if the weir can surcharge (have an upstream water level higher than
the height of the opening); NO if it cannot (default is YES).
Width width of road lanes and shoulders for ROADWAY weir (ft or m).
Surface type of road surface for ROADWAY weir: PAVED or GRAVEL.
The geometry of a weir’s opening is described in the [XSECTIONS] section. The
following shapes must be used with each type of weir:
Weir Type Cross-Section Shape
Transverse RECT_OPEN
Sideflow RECT_OPEN
V-Notch TRIANGULAR
Trapezoidal TRAPEZOIDAL
Roadway RECT_OPEN
The ROADWAY weir is a broad crested rectangular weir used model roadway
crossings usually in conjunction with culvert-type conduits. It uses the FHWA HDS-5
method to determine a discharge coefficient as a function of flow depth and roadway
width and surface. If no roadway data are provided then the weir behaves as a
TRANSVERSE weir with Cd as its discharge coefficient. Note that if roadway data are
provided, then values for the other optional weir parameters (NO for Gated, 0 for
EC, 0 for Cd2, and NO for Sur) must be entered even though they do not apply to
ROADWAY weirs. Section: [OUTLETS] Purpose: Identifies each outlet flow control device of the drainage system. These devices are
used to model outflows from storage units or flow diversions that have a user-defined
relation between flow rate and water depth. Formats: Name Node1 Node2 Offset TABULAR/DEPTH Qcurve (Gated) Name Node1 Node2 Offset TABULAR/HEAD Qcurve (Gated)
Name Node1 Node2 Offset FUNCTIONAL/DEPTH C1 C2 (Gated)
Name Node1 Node2 Offset FUNCTIONAL/HEAD C1 C2 (Gated)
Remarks: Name name assigned to outlet link.
Node1 name of node on inlet end of link.
Node2 name of node on outflow end of link.
Offset amount that the outlet is offset above the invert of inlet node (ft or m,
expressed as either a depth or as an elevation, depending on the
LINK_OFFSETS option setting).
Qcurve name of the rating curve listed in the [CURVES] section that describes
outflow rate (flow units) as a function of:
 water depth above the offset elevation at the inlet node (ft or m) for a
TABULAR/DEPTH outlet
 head difference (ft or m) between the inlet and outflow nodes for a
TABULAR/HEAD outlet.
C1, C2 coefficient and exponent, respectively, of a power function that relates
outflow (Q) to:
 water depth (ft or m) above the offset elevation at the inlet node for a
FUNCTIONAL/DEPTH outlet
 head difference (ft or m) between the inlet and outflow nodes for a
FUNCTIONAL/HEAD outlet.
(i.e., 푄푄=퐶퐶 1 퐻퐻퐶퐶2 where H^ is either depth or head).^
Gated YES if flap gate present to prevent reverse flow, NO if not (default is NO).
Section: [XSECTIONS] Purpose: Provides cross-section geometric data for conduit and regulator links of the drainage
system. Formats: Link Shape Geom1 Geom2 Geom3 Geom4 (Barrels Culvert)
Link CUSTOM Geom1 Curve (Barrels)
Link IRREGULAR Tsect
Remarks: Link name of the conduit, orifice, or weir.
Shape cross-section shape (see Tables D-1 below or 3-1 for available shapes).
Geom1 full height of the cross-section (ft or m).
Geom2-4 auxiliary parameters (width, side slopes, etc.) as listed in Table D-1.
Barrels number of barrels (i.e., number of parallel pipes of equal size, slope, and
roughness) associated with a conduit (default is 1).
Culvert code number from Table A.10 for the conduit’s inlet geometry if it is a
culvert subject to possible inlet flow control (leave blank otherwise).
Curve name of a Shape Curve in the [CURVES] section that defines how width
varies with depth.
Tsect name of an entry in the [TRANSECTS] section that describes the cross-
section geometry of an irregular channel.
The Culvert c ode number is used only for conduits that act as culverts and should be
analyzed for inlet control conditions using the FHWA HDS-5 method.
The CUSTOM shape is a closed conduit whose width versus height is described by a
user-supplied Shape Curve.
An IRREGULAR cross-section is used to model an open channel whose geometry is
described by a Transect object.

TABLE D-1 GEOMETRIC PARAMETERS OF CONDUIT CROSS SECTIONS

Shape Geom1 Geom2 Geom3 Geom4 CIRCULAR Diameter FORCE_MAIN^ Diameter Roughness^1 FILLED_CIRCULAR^2 Diameter Sediment Depth RECT_CLOSED Full Height Top Width RECT_OPEN Full Height Top Width TRAPEZOIDAL Full Height Base Width Left Slope^3 Right Slope^3 TRIANGULAR Full Height Top Width HORIZ_ELLIPSE Full Height Max. Width Size Code^4 VERT_ELLIPSE Full Height Max. Width Size Code^4 ARCH Full Height Max. Width Size Code^5 PARABOLIC Full Height Top Width POWER Full Height Top Width Exponent RECT_TRIANGULAR Full Height Top Width Triangle Height RECT_ROUND Full Height Top Width Bottom Radius MODBASKETHANDLE Full Height Base Width Top Radius^6 EGG Full Height HORSESHOE Full Height GOTHIC Full Height CATENARY Full Height SEMIELLIPTICAL Full Height BASKETHANDLE Full Height SEMICIRCULAR Full Height (^1) C- factors are used when H-W is the FORCE_MAIN_EQUATION choice in the [OPTIONS]
section while roughness heights (in inches or mm) are used for D-W.
(^2) A circular conduit partially filled with sediment to a specified depth.
(^3) Slopes are horizontal run / vertical rise.
(^4) Size code of a standard shaped elliptical pipe as listed in Appendix A11. Leave blank (or
0) if the pipe has a custom dimensions.
(^5) Size code of a standard arch pipe as listed in Appendix A12. Leave blank (or 0) if the
pipe has custom dimensions).
(^6) Set to zero to use a standard modified baskethandle shape whose top radius is half the
base width. Section: [LOSSES] Purpose: Specifies minor head loss coefficients, flap gates, and seepage rates for conduits. Formats: Conduit Kentry Kexit Kavg (Flap Seepage) Remarks: Conduit name of conduit.
Kentry entrance minor head loss coefficient.
Kexit exit minor head loss coefficient.
Kavg average minor head loss coefficient across length of conduit.
Flap YES if conduit has a flap valve that prevents back flow, NO otherwise.
(Default is NO).
Seepage Rate of seepage loss into surrounding soil (in/hr or mm/hr). (Default is 0.)
Minor losses are only computed for the Dynamic Wave flow routing option (see
[OPTIONS] section). They are computed as Kv^2 /2g where K = minor loss coefficient, v
= velocity, and g = acceleration of gravity. Entrance losses are based on the velocity
at the entrance of the conduit, exit losses on the exit velocity, and average losses on
the average velocity.
Only enter data for conduits that actually have minor losses, flap valves, or seepage
losses.
Section: [TRANSECTS] Purpose: Describes the cross-section geometry of natural channels or conduits with irregular
shapes following the HEC-2 data format. Formats: NC Nleft Nright Nchanl
X1 Name Nsta Xleft Xright 0 0 0 Lfactor Wfactor Eoffset
GR Elev Station ... Elev Station
Remarks: Nleft Manning’s n of right overbank portion of channel (use 0 if no change
from previous NC line).
Nright Manning’s n of right overbank portion of channel (use 0 if no change
from previous NC line.
Nchanl Manning’s n of main channel portion of channel (use 0 if no change from
previous NC line.
Name name assigned to transect.
Nsta number of stations across cross-section at which elevation data is
supplied.
Xleft station position which ends the left overbank portion of the channel (ft or
m).
Xright station position which begins the right overbank portion of the channel (ft
or m).
Lfactor meander modifier that represents the ratio of the length of a meandering
main channel to the length of the overbank area that surrounds it (use 0
if not applicable).
Wfactor factor by which distances between stations should be multiplied to
increase (or decrease) the width of the channel (enter 0 if not
applicable).
Eoffset amount added (or subtracted) from the elevation of each station (ft or m).
Elev elevation of the channel bottom at a cross-section station relative to
some fixed reference (ft or m).
Station distance of a cross-section station from some fixed reference (ft or m).
Transect geometry is described as shown below, assuming that one is looking in a
downstream direction:
The first line in this section must always be a NC line. After that, the NC line is only
needed when a transect has different Manning’s n values than the previous one. The Manning’s n values on the NC line will supersede any roughness value entered
for the conduit which uses the irregular cross-section. There should be one X1 line for each transect. Any number of GR lines may follow,
and each GR line can have any number of Elevation-Station data pairs. (In HEC-2 the
GR line is limited to 5 stations.) The station that defines the left overbank boundary on the X1 line must correspond to
one of the station entries on the GR lines that follow. The same holds true for the right
overbank boundary. If there is no match, a warning will be issued and the program
will assume that no overbank area exists. The meander modifier is applied to all conduits that use this particular transect for
their cross section. It assumes that the length supplied for these conduits is that of
the longer main channel. SWMM will use the shorter overbank length in its
calculations while increasing the main channel roughness to account for its longer
length. Section: [CONTROLS] Purpose: Determines how pumps and regulators will be adjusted based on simulation time or
conditions at specific nodes and links. Formats: Each control rule is a series of statements of the form:
RULE ruleID
IF condition_1
AND condition_2
OR condition_3
AND condition_4
Etc.
THEN action_1
AND action_2
Etc.
ELSE action_3
AND action_4
Etc.
PRIORITY value
Remarks: RuleID an ID label assigned to the rule.
condition_n a condition clause.
action_n an action clause.
value a priority value (e.g., a number from 1 to 5).
A condition clause of a Control Rule has the following format:
Object Name Attribute Relation Value
where Object is a category of object, Name is the object’s assigned ID name,
Attribute is the name of an attribute or property of the object, Relation is a
relational operator (=, <>, <, <=, >, >=), and Value is an attribute value.
Some examples of condition clauses are:
NODE N23 DEPTH > 10
PUMP P45 STATUS = OFF
SIMULATION TIME = 12:45:00
The objects and attributes that can appear in a condition clause are as follows:
Object Attributes Value
NODE DEPTH
HEAD
VOLUME
INFLOW
numerical value
numerical value
numerical value
numerical value
LINK FLOW
DEPTH
TIMEOPEN
TIMECLOSED
numerical value
numerical value
decimal hours or hr:min
decimal hours or hr:min
CONDUIT STATUS
TIMEOPEN
TIMECLOSED
OPEN or CLOSED
decimal hours or hr:min
decimal hours or hr:min
PUMP STATUS
SETTING
FLOW
TIMEOPEN
TIMECLOSED
ON or OFF
pump curve multiplier
numerical value
decimal hours or hr:min
decimal hours or hr:min
ORIFICE SETTING
TIMEOPEN
TIMECLOSED
fraction open
decimal hours or hr:min
decimal hours or hr:min
WEIR SETTING
TIMEOPEN
TIMECLOSED
fraction open
decimal hours or hr:min
decimal hours or hr:min
OUTLET SETTING
TIMEOPEN
TIMECLOSED
rating curve multiplier
decimal hours or hr:min
decimal hours or hr:min
SIMULATION TIME elapsed time in decimal hours or
hr:min:sec
SIMULATION DATE
MONTH
DAY
CLOCKTIME
month/day/year
month of year (January = 1)
day of week (Sunday = 1)
time of day in hr:min:sec
TIMEOPEN is the duration a link has been in an OPEN or ON state or have its
SETTING be greater than zero; TIMECLOSED is the duration it has remained in a
CLOSED or OFF state or have its SETTING be zero. An action clause of a Control Rule can have one of the following formats: PUMP id STATUS = ON/OFF PUMP/ORIFICE/WEIR/OUTLET id SETTING = value where the meaning of SETTING depends on the object being controlled: ▪ for Pumps it is a multiplier applied to the flow computed from the pump curve, ▪ for Orifices it is the fractional amount that the orifice is fully open, ▪ for Weirs it is the fractional amount of the original freeboard that exists (i.e., weir
control is accomplished by moving the crest height up or down), ▪ for Outlets it is a multiplier applied to the flow computed from the outlet’s rating
curve. Modulated controls are control rules that provide for a continuous degree of control
applied to a pump or flow regulator as determined by the value of some controller
variable, such as water depth at a node, or by time. The functional relation between
the control setting and the controller variable is specified by using a control curve, a
time series, or a PID controller. To model these types of controls, the value entry on
the right-hand side of the action clause is replaced by the keyword CURVE,
TIMESERIES, or PID and followed by the id name of the respective control curve or
time series or by the gain, integral time (in minutes), and derivative time (in minutes)
of a PID controller. For direct action control the gain is a positive number while for
reverse action control it must be a negative number. By convention, the controller
variable used in a control curve or PID control will always be the object and attribute
named in the last condition clause of the rule. The value specified for this clause will
be the setpoint used in a PID controller. Some examples of action clauses are:
PUMP P67 STATUS = OFF
ORIFICE O212 SETTING = 0.5
WEIR W25 SETTING = CURVE C25
ORIFICE ORI_23 SETTING = PID 0.1 0.1 0.0
Only the RULE, IF and THEN portions of a rule are required; the other portions are
optional. When mixing AND and OR clauses, the OR operator has higher precedence
than AND, i.e.,
IF A or B and C
is equivalent to
IF (A or B) and C.
If the interpretation was meant to be
IF A or (B and C)
then this can be expressed using two rules as in

IF A THEN …

IF B and C THEN ...
The PRIORITY value is used to determine which rule applies when two or more rules
require that conflicting actions be taken on a link. A conflicting rule with a higher
priority value has precedence over one with a lower value (e.g., PRIORITY 5
outranks PRIORITY 1). A rule without a priority value always has a lower priority
than one with a value. For two rules with the same priority value, the rule that
appears first is given the higher priority.
Examples: ; Simple time-based pump control
RULE R1
IF SIMULATION TIME > 8
THEN PUMP 12 STATUS = ON
ELSE PUMP 12 STATUS = OFF
; Multi-condition orifice gate control
RULE R2A
IF NODE 23 DEPTH > 12
AND LINK 165 FLOW > 100
THEN ORIFICE R55 SETTING = 0.5
RULE R2B
IF NODE 23 DEPTH > 12
AND LINK 165 FLOW > 200
THEN ORIFICE R55 SETTING = 1.0
RULE R2C
IF NODE 23 DEPTH <= 12
OR LINK 165 FLOW <= 100
THEN ORIFICE R55 SETTING = 0
; PID controller that attempts to keep Node 23’s depth at 12:
RULE PID_1
IF NODE 23 DEPTH <> 12
THEN ORIFICE R55 SETTING = PID 0.5 0.1 0.0
; Pump station operation with a main (N1A) and lag (N1B) pump
RULE R3A
IF NODE N1 DEPTH > 5
THEN PUMP N1A STATUS = ON
RULE R3B
IF PUMP N1A TIMEOPEN > 2:30
THEN PUMP N1B STATUS = ON
ELSE PUMP N1B STATUS = OFF

RULE R3C

IF NODE N1 DEPTH <= 0.5

THEN PUMP N1A STATUS = OFF

AND PUMP N1B STATUS = OFF

Section: [POLLUTANTS] Purpose: Identifies the pollutants being analyzed. Format:
Name Units Crain Cgw Cii Kd (Sflag CoPoll CoFract Cdwf Cinit) Remarks: Name name assigned to pollutant.
Units concentration units (MG/L for milligrams per liter, UG/L for micrograms
per liter, or #/L for direct count per liter).
Crain concentration of pollutant in rainfall (concentration units).
Cgw concentration of pollutant in groundwater (concentration units).
Cii concentration of pollutant in inflow/infiltration (concentration units).
Kdecay first-order decay coefficient (1/days).
Sflag YES if pollutant buildup occurs only when there is snow cover, NO
otherwise (default is NO).
CoPoll name of co-pollutant (default is no co-pollutant designated by a *).
CoFract fraction of co-pollutant concentration (default is 0).
Cdwf pollutant concentration in dry weather flow (default is 0).
Cinit pollutant concentration throughout the conveyance system at the start of
the simulation (default is 0).
FLOW is a reserved word and cannot be used to name a pollutant.
Parameters Sflag through Cinit can be omitted if they assume their default
values. If there is no co-pollutant but non-default values for Cdwf or Cinit, then
enter an asterisk (*) for the co-pollutant name.
When pollutant X has a co-pollutant Y, it means that fraction CoFract of pollutant Y’s
runoff concentration is added to pollutant X’s runoff concentration when wash off from
a subcatchment is computed.
The dry weather flow concentration can be overridden for any specific node of the
conveyance system by editing the node’s Inflows property.
Section: [LANDUSES] Purpose: Identifies the various categories of land uses within the drainage area. Each
subcatchment area can be assigned a different mix of land uses. Each land use can
be subjected to a different street sweeping schedule. Format: Name (SweepInterval Availability LastSweep) Remarks: Name land use name.
SweepInterval days between street sweeping.
Availability fraction of pollutant buildup available for removal by street
sweeping.
LastSweep days since last sweeping at start of the simulation.
Section: [COVERAGES] Purpose: Specifies the percentage of a subcatchment’s area that is covered by each category
of land use. Format: Subcat Landuse Percent Landuse Percent… Remarks: Subcat subcatchment name.
Landuse land use name.
Percent percent of subcatchment area.
More than one pair of land use - percentage values can be entered per line. If more
than one line is needed, then the subcatchment name must still be entered first on
the succeeding lines.
If a land use does not pertain to a subcatchment, then it does not have to be entered.
If no land uses are associated with a subcatchment then no contaminants will appear
in the runoff from the subcatchment.
Section: [LOADINGS] Purpose: Specifies the pollutant buildup that exists on each subcatchment at the start of a
simulation. Format: Subcat Pollut InitBuildup Pollut InitBuildup … Remarks: Subcat name of a subcatchment.
Pollut name of a pollutant.
InitBuildup initial buildup of pollutant (lbs/acre or kg/hectare).
More than one pair of pollutant - buildup values can be entered per line. If more than
one line is needed, then the subcatchment name must still be entered first on the
succeeding lines.
If an initial buildup is not specified for a pollutant, then its initial buildup is computed
by applying the DRY_DAYS option (specified in the [OPTIONS] section) to the
pollutant’s buildup function for each land use in the subcatchment.
Section: [BUILDUP] Purpose: Specifies the rate at which pollutants build up over different land uses between rain
events. Format: Landuse Pollutant FuncType C1 C2 C3 PerUnit Remarks: Landuse land use name.
Pollutant pollutant name.
FuncType buildup function type: ( POW / EXP / SAT / EXT ).
C1,C2,C3 buildup function parameters (see Table D-2).
PerUnit AREA if buildup is per unit area, CURBLENGTH if per length of curb.
Buildup is measured in pounds (kilograms) per unit of area (or curb length) for
pollutants whose concentration units are either mg/L or ug/L. If the concentration
units are counts/L, then the buildup is expressed as counts per unit of area (or curb
length).

TABLE D-2 POLLUTANT BUILDUP FUNCTIONS (T IS ANTECEDENT DRY DAYS)

Name Function Equation
POW Power Min (C1, C2*tC3)
EXP Exponential C1*(1 – exp(-C2*t))
SAT Saturation C1*t / (C3 + t)
EXT External See below
For the EXT buildup function, C1 is the maximum possible buildup (mass per area or
curb length), C2 is a scaling factor, and C3 is the name of a Time Series that
contains buildup rates (as mass per area or curb length per day) as a function of
time.
Section: [WASHOFF] Purpose: Specifies the rate at which pollutants are washed off from different land uses during
rain events. Format: Landuse Pollutant FuncType C1 C2 SweepRmvl BmpRmvl Remarks: Landuse land use name.
Pollutant pollutant name.
FuncType washoff function type: EXP / RC / EMC.
C1, C2 washoff function coefficients(see Table D-3).
SweepRmvl street sweeping removal efficiency (percent).
BmpRmvl BMP removal efficiency (percent).

TABLE D-3 POLLUTANT WASH OFF FUNCTIONS

Name Function Equation Units
EXP Exponential C1 (runoff)C2 (buildup) Mass/hour
RC Rating Curve C1 (runoff)C2 Mass/sec

EMC

Event Mean
Concentration
C1 Mass/Liter
Each washoff function expresses its results in different units.
For the Exponential function the runoff variable is expressed in catchment depth
per unit of time (inches per hour or millimeters per hour), while for the Rating Curve
function it is in whatever flow units were specified in the [OPTIONS] section of the
input file (e.g., CFS, CMS, etc.).
The buildup parameter in the Exponential function is the current total buildup over
the subcatchment’s land use area in mass units. The units of C1 in the Exponential
function are (in/hr) -C2 per hour (or (mm/hr) -C2 per hour). For the Rating Curve
function, the units of C1 depend on the flow units employed. For the EMC (event
mean concentration) function, C1 is always in concentration units.
Section: [TREATMENT] Purpose: Specifies the degree of treatment received by pollutants at specific nodes of the
drainage system. Format: Node Pollut Result = Func Remarks: Node Name of node where treatment occurs.
Pollut Name of pollutant receiving treatment.
Result Result computed by treatment function. Choices are:
C ( function computes effluent concentration)
R ( function computes fractional removal).
Func mathematical function expressing treatment result in terms of pollutant
concentrations, pollutant removals, and other standard variables (see
below).
Treatment functions can be any well-formed mathematical expression involving:
▪ inlet pollutant concentrations (use the pollutant name to represent a
concentration)
▪ removal of other pollutants (use R_ pre-pended to the pollutant name to
represent removal)
▪ process variables which include:
FLOW for flow rate into node (user’s flow units)
DEPTH for water depth above node invert (ft or m)
AREA for node surface area (ft2 or m2)
DT for routing time step (seconds)
HRT for hydraulic residence time (hours)
Any of the following math functions can be used in a treatment function:
  • abs(x) for absolute value of x
  • sgn(x) which is +1 for x >= 0 or -1 otherwise
  • step(x) which is 0 for x <= 0 and 1 otherwise
  • sqrt(x) for the square root of x
  • log(x) for logarithm base e of x
  • log10(x) for logarithm base 10 of x
  • exp(x) for e raised to the x power
  • the standard trig functions (sin, cos, tan, and cot)
  • the inverse trig functions (asin, acos, atan, and acot)
  • the hyperbolic trig functions (sinh, cosh, tanh, and coth)
    along with the standard operators +, -, *, /, ^ (for exponentiation ) and any level of
    nested parentheses.
Examples: ; 1-st order decay of BOD
Node23 BOD C = BOD * exp(-0.05*HRT)
; lead removal is 20% of TSS removal
Node23 Lead R = 0.2 * R_TSS
Section: [INFLOWS] Purpose: Specifies external hydrographs and pollutographs that enter the drainage system at
specific nodes. Formats: Node FLOW Tseries (FLOW (1.0 Sfactor Base Pat))
Node Pollut Tseries ( Type (Mfactor Sfactor Base Pat)) Remarks: Node name of node where external inflow enters.
Pollut name of pollutant.
Tseries name of time series in [TIMESERIES] section describing how
external flow or pollutant loading varies with time.
Type CONCEN if pollutant inflow is described as a concentration, MASS
if it is described as a mass flow rate (default is CONCEN).
Mfactor the factor that converts the inflow’s mass flow rate units into the
project’s mass units per second, where the project’s mass units
are those specified for the pollutant in the [POLLUTANTS] section
(default is 1.0 - see example below).
Sfactor scaling factor that multiplies the recorded time series values
(default is 1.0).
Base constant baseline value added to the time series value (default is
0.0).
Pat name of optional time pattern in [PATTERNS] section used to
adjust the baseline value on a periodic basis.
External inflows are represented by both a constant and time varying component as
follows:
Inflow = (Baseline value)*(Pattern factor) +
(Scaling factor)*(Time series value)
If an external inflow of a pollutant concentration is specified for a node, then there
must also be an external inflow of FLOW provided for the same node, unless the node
is an Outfall. In that case a pollutant can enter the system during periods when the
outfall is submerged and reverse flow occurs.
Examples: NODE2 FLOW N2FLOW
NODE33 TSS N33TSS CONCEN
;Mass inflow of BOD in time series N65BOD given in lbs/hr
;(126 converts lbs/hr to mg/sec)
NODE65 BOD N65BOD MASS 126
;Flow inflow with baseline and scaling factor
N176 FLOW FLOW_176 FLOW 1.0 0.5 12.7 FlowPat
Section: [DWF] Purpose: Specifies dry weather flow and its quality entering the drainage system at specific
nodes. Format: Node Type Base (Pat1 Pat2 Pat3 Pat4) Remarks: Node name of node where dry weather flow enters.
Type keyword FLOW for flow or pollutant name for quality constituent.
Base average baseline value for corresponding constituent (flow or
concentration units).
Pat1,
Pat2,
etc. names of up to four time patterns appearing in the [PATTERNS] section.
The actual dry weather input will equal the product of the baseline value and any
adjustment factors supplied by the specified patterns. (If not supplied, an adjustment
factor defaults to 1.0.)
The patterns can be any combination of monthly, daily, hourly and weekend hourly
patterns, listed in any order. See the [PATTERNS] section for more details.
Section: [RDII] Purpose: Specifies the parameters that describe rainfall-dependent infiltration/inflow (RDII)
entering the drainage system at specific nodes. Format: Node UHgroup SewerArea Remarks: Node name of a node.
UHgroup name of an RDII unit hydrograph group specified in the
[HYDROGRAPHS] section.
SewerArea area of the sewershed which contributes RDII to the node (acres or
hectares).
Section: [HYDROGRAPHS] Purpose: Specifies the shapes of the triangular unit hydrographs that determine the amount of
rainfall-dependent infiltration/inflow (RDII) entering the drainage system. Formats: Name Raingage Name Month SHORT/MEDIUM/LONG R T K (Dmax Drec D0) Remarks: Name name assigned to a unit hydrograph group.
Raingage name of the rain gage used by the unit hydrograph group.
Month month of the year (e.g., JAN, FEB, etc. or ALL for all months).
R response ratio for the unit hydrograph.
T time to peak (hours) for the unit hydrograph.
K recession limb ratio for the unit hydrograph.
Dmax maximum initial abstraction depth available (in rain depth units).
Drec initial abstraction recovery rate (in rain depth units per day)
D0 initial abstraction depth already filled at the start of the simulation (in
rain depth units).
For each group of unit hydrographs, use one line to specify its rain gage followed by
as many lines as are needed to define each unit hydrograph used by the group
throughout the year. Three separate unit hydrographs, that represent the short-term,
medium-term, and long-term RDII responses, can be defined for each month (or all
months taken together). Months not listed are assumed to have no RDII.
The response ratio (R) is the fraction of a unit of rainfall depth that becomes RDII.
The sum of the ratios for a set of three hydrographs does not have to equal 1.0.
The recession limb ratio (K) is the ratio of the duration of the hydrograph’s recession
limb to the time to peak (T) making the hydrograph time base equal to T*(1+K) hours.
The area under each unit hydrograph is 1 inch (or mm).
The optional initial abstraction parameters determine how much rainfall is lost at the
start of a storm to interception and depression storage. If not supplied then the
default is no initial abstraction.
Examples: ; All three unit hydrographs in this group have the same shapes except those in July,
; which have only a short- and medium-term response and a different shape.
UH101 RG1
UH101 ALL SHORT 0.033 1.0 2.0
UH101 ALL MEDIUM 0.300 3.0 2.0
UH101 ALL LONG 0.033 10.0 2.0
UH101 JUL SHORT 0.033 0.5 2.0
UH101 JUL MEDIUM 0.011 2.0 2.0 Section: [CURVES] Purpose: Describes a relationship between two variables in tabular format. Format: Name Type X-value Y-value … Remarks: Name name assigned to table
Type STORAGE / SHAPE / DIVERSION / TIDAL / PUMP1 / PUMP2 /
PUMP3 / PUMP4 / RATING / CONTROL
X- value an x (independent variable) value
Y- value the y (dependent variable) value corresponding to x
Multiple pairs of x-y values can appear on a line. If more than one line is needed,
repeat the curve's name (but not the type) on subsequent lines. The x-values must
be entered in increasing order.
Choices for curve type have the following meanings (flows are expressed in the
user’s choice of flow units set in the [OPTIONS] section):
STORAGE surface area in ft^2 (m^2 ) v. depth in ft (m) for a storage unit node
SHAPE width v. depth for a custom closed cross-section, both
normalized with respect to full depth
DIVERSION diverted outflow v. total inflow for a flow divider node
TIDAL water surface elevation in ft (m) v. hour of the day for an outfall
node
PUMP1 pump outflow v. increment of inlet node volume in ft^3 (m^3 )
PUMP2 pump outflow v. increment of inlet node depth in ft (m)
PUMP3 pump outflow v. head difference between outlet and inlet nodes
in ft (m)
PUMP4 pump outflow v. continuous depth in ft (m)
RATING outlet flow v. head in ft (m)
CONTROL control setting v. controller variable
See Section 3.2 for illustrations of the different types of pump curves.
Examples: ;Storage curve (x = depth, y = surface area)
AC1 STORAGE 0 1000 2 2000 4 3500 6 4200 8 5000
;Type1 pump curve (x = inlet wet well volume, y = flow )
PC1 PUMP1
PC1 100 5 300 10 500 20
Section: [TIMESERIES] Purpose: Describes how a quantity varies over time. Formats: Name ( Date ) Hour Value …
Name Time Value ...
Name FILE Fname
Remarks: Name name assigned to time series.
Date date in Month/Day/Year format (e.g., June 15, 2001 would be
6/15/2001).
Hour 24-hour military time (e.g., 8:40 pm would be 20:40) relative to the last
date specified (or to midnight of the starting date of the simulation if no
previous date was specified).
Time hours since the start of the simulation, expressed as a decimal number
or as hours:minutes.
Value value corresponding to given date and time.
Fname name of a file in which the time series data are stored
There are two options for supplying the data for a time series:
i. directly within this input file section as described by the first two formats
ii. through an external data file named with the third format.
When direct data entry is used, multiple date-time-value or time-value entries can
appear on a line. If more than one line is needed, the table's name must be repeated
as the first entry on subsequent lines.
When an external file is used, each line in the file must use the same formats listed
above, except that only one date-time-value (or time-value) entry is allowed per line.
Any line that begins with a semicolon is considered a comment line and is ignored.
Blank lines are not allowed.
Note that there are two methods for describing the occurrence time of time series
data:
▪ as calendar date/time of day (which requires that at least one date, at the start of
the series, be entered)
▪ as elapsed hours since the start of the simulation.
For the first method, dates need only be entered at points in time when a new day
occurs.
Examples: ;Rainfall time series with dates specified
TS1 6-15- 2001 7:00 0.1 8:00 0.2 9:00 0.05 10:00 0
TS1 6-21- 2001 4:00 0.2 5:00 0 14:00 0.1 15:00 0 ;Inflow hydrograph – time relative to start of simulation
HY1 0 0 1.25 100 2:30 150 3.0 120 4.5 0
HY1 32:10 0 34.0 57 35.33 85 48.67 24 50 0 Section: [PATTERNS] Purpose: Specifies time pattern of dry weather flow or quality in the form of adjustment factors
applied as multipliers to baseline values. Format: Name MONTHLY Factor1 Factor2 … Factor12
Name DAILY Factor1 Factor2 ... Factor7
Name HOURLY Factor1 Factor2 ... Factor24
Name WEEKEND Factor1 Factor2 ... Factor24
Remarks: Name name used to identify the pattern.
Factor1,
Factor2,
etc. multiplier values.
The MONTHLY format is used to set monthly pattern factors for dry weather flow
constituents.
The DAILY format is used to set dry weather pattern factors for each day of the
week, where Sunday is day 1.
The HOURLY format is used to set dry weather factors for each hour of the day
starting from midnight. If these factors are different for weekend days than for
weekday days then the WEEKEND format can be used to specify hourly adjustment
factors just for weekends.
More than one line can be used to enter a pattern’s factors by repeating the pattern’s
name (but not the pattern type) at the beginning of each additional line.
The pattern factors are applied as multipliers to any baseline dry weather flows or
quality concentrations supplied in the [DWF] section.
Examples: ; Day of week adjustment factors
D1 DAILY 0.5 1.0 1.0 1.0 1.0 1.0 0.5
D2 DAILY 0.8 0.9 1.0 1.1 1.0 0.9 0.8
; Hourly adjustment factors
H1 HOURLY 0.5 0.6 0.7 0.8 0.8 0.9
H1 1.1 1.2 1.3 1.5 1.1 1.0
H1 0.9 0.8 0.7 0.6 0.5 0.5
H1 0.5 0.5 0.5 0.5 0.5 0.5
D3. Map Data Section SWMM’s graphical user interface (GUI) can display a schematic map of the drainage area being
analyzed. This map displays subcatchments as polygons, nodes as circles, links as polylines, and
rain gages as bitmap symbols. In addition it can display text labels and a backdrop image, such
as a street map. The GUI has tools for drawing, editing, moving, and displaying these map
elements. The map’s coordinate data are stored in the format described below. Normally these
data are simply appended to the SWMM input file by the GUI so users do not have to concern
themselves with it. However it is sometimes more convenient to import map data from some other
source, such as a CAD or GIS file, rather than drawing a map from scratch using the GUI. In this
case the data can be added to the SWMM project file using any text editor or spreadsheet
program. SWMM does not provide any automated facility for converting coordinate data from
other file formats into the SWMM map data format. SWMM’s map data are organized into the following seven sections:
[MAP] X,Y coordinates of the map’s bounding rectangle
[POLYGONS] X,Y coordinates for each vertex of subcatchment polygons
[COORDINATES] X,Y coordinates for nodes
[VERTICES] X,Y coordinates for each interior vertex of polyline links
[LABELS] X,Y coordinates and text of labels
[SYMBOLS] X,Y coordinates for rain gages
[BACKDROP] X,Y coordinates of the bounding rectangle and file name of the backdrop
image.
Figure D-2 displays a sample map and Figure D-3 the data that describes it. Note that only one
link, 3, has interior vertices which give it a curved shape. Also observe that this map’s coordinate
system has no units, so that the positions of its objects may not necessarily coincide to their real-
world locations.
Figure D-2 Example study area map
[MAP]
DIMENSIONS 0.00 0.00 10000.00 10000.00
UNITS None
[COORDINATES]
;;Node X-Coord Y-Coord
N1 4006.62 5463.58
N2 6953.64 4768.21
N3 4635.76 3443.71
N4 8509.93 827.81
[VERTICES]
;;Link X-Coord Y-Coord
3 5430.46 2019.87
3 7251.66 927.15
[SYMBOLS]
;;Gage X-Coord Y-Coord
G1 5298.01 9139.07
[Polygons]
;;Subcatchment X-Coord Y-Coord
S1 3708.61 8543.05
S1 4834.44 7019.87
S1 3675.50 4834.44
< additional vertices not listed >
S2 6523.18 8079.47
S2 8112.58 8841.06
Figure D-3 Data for example study area map
A detailed description of each map data section will now be given. Remember that map data are
only used as a visualization aid for SWMM’s GUI and they play no role in any of the runoff or
routing computations. Map data are not needed for running the command line version of SWMM. Section: [MAP] Purpose: Provides dimensions and distance units for the map. Formats: DIMENSIONS X1 Y1 X2 Y2
UNITS FEET / METERS / DEGREES / NONE Remarks: X1 lower-left X coordinate of full map extent
Y1 lower-left Y coordinate of full map extent
X2 upper-right X coordinate of full map extent
Y2 upper-right Y coordinate of full map extent Section: [COORDINATES] Purpose: Assigns X,Y coordinates to drainage system nodes. Format: Node Xcoord Ycoord Remarks: Node name of node.
Xcoord horizontal coordinate relative to origin in lower left of map.
Ycoord vertical coordinate relative to origin in lower left of map. Section: [VERTICES] Purpose: Assigns X,Y coordinates to interior vertex points of curved drainage system links. Format: Link Xcoord Ycoord Remarks: Link name of link.
Xcoord horizontal coordinate of vertex relative to origin in lower left of map.
Ycoord vertical coordinate of vertex relative to origin in lower left of map.
Include a separate line for each interior vertex of the link, ordered from the inlet node
to the outlet node.
Straight-line links have no interior vertices and therefore are not listed in this section.
Section: [POLYGONS] Purpose: Assigns X,Y coordinates to vertex points of polygons that define a subcatchment
boundary. Format: Subcat Xcoord Ycoord Remarks: Subcat name of subcatchment.
Xcoord horizontal coordinate of vertex relative to origin in lower left of map.
Ycoord vertical coordinate of vertex relative to origin in lower left of map.
Include a separate line for each vertex of the subcatchment polygon, ordered in a
consistent clockwise or counter-clockwise sequence.
Section: [SYMBOLS] Purpose: Assigns X,Y coordinates to rain gage symbols. Format: Gage Xcoord Ycoord Remarks: Gage name of rain gage.
Xcoord horizontal coordinate relative to origin in lower left of map.
Ycoord vertical coordinate relative to origin in lower left of map. Section: [LABELS] Purpose: Assigns X,Y coordinates to user-defined map labels. Format: Xcoord Ycoord Label (Anchor Font Size Bold Italic) Remarks: Xcoord horizontal coordinate relative to origin in lower left of map.
Ycoord vertical coordinate relative to origin in lower left of map.
Label text of label surrounded by double quotes.
Anchor name of node or subcatchment that anchors the label on zoom-ins (use
an empty pair of double quotes if there is no anchor).
Font name of label’s font (surround by double quotes if the font name includes
spaces).
Size font size in points.
Bold YES for bold font, NO otherwise.
Italic YES for italic font, NO otherwise.
Use of the anchor node feature will prevent the label from moving outside the viewing
area when the map is zoomed in on.
If no font information is provided then a default font is used to draw the label.
Section: [BACKDROP] Purpose: Specifies file name and coordinates of map’s backdrop image. Formats: FILE Fname
DIMENSIONS X1 Y1 X2 Y2 Remarks: Fname name of file containing backdrop image
X1 lower-left X coordinate of backdrop image
Y1 lower-left Y coordinate of backdrop image
X2 upper-right X coordinate of backdrop image
Y2 upper-right Y coordinate of backdrop image

APPENDIX E – ERROR AND WARNING MESSAGES

ERROR 101: memory allocation error.
There is not enough physical memory in the computer to analyze the study area. ERROR 103: cannot solve KW equations for Link xxx.
The internal solver for Kinematic Wave routing failed to converge for the
specified link at some stage of the simulation. ERROR 105: cannot open ODE solver.
The system could not open its Ordinary Differential Equation solver. ERROR 107: cannot compute a valid time step.
A valid time step for runoff or flow routing calculations (i.e., a number greater
than 0) could not be computed at some stage of the simulation. ERROR 108: ambiguous outlet ID name for Subcatchment xxx.
The name of the element identified as the outlet of a subcatchment belongs to
both a node and a subcatchment in the project’s data base. ERROR 109: invalid parameter values for Aquifer xxx.
The properties entered for an aquifer object were either invalid numbers or were
inconsistent with one another (e.g., the soil field capacity was higher than the
porosity). ERROR 110: ground elevation is below water table for Subcatchment xxx.
The ground elevation assigned to a subcatchment’s groundwater parameters
cannot be below the initial water table elevation of the aquifer object used by the
subcatchment. ERROR 111: invalid length for Conduit xxx.
Conduits cannot have zero or negative lengths. ERROR 113: invalid roughness for Conduit xxx.
Conduits cannot have zero or negative roughness values. ERROR 114: invalid number of barrels for Conduit xxx.
Conduits must consist of one or more barrels. ERROR 115: adverse slope for Conduit xxx.
Under Steady or Kinematic Wave routing, all conduits must have positive slopes.
This can usually be corrected by reversing the inlet and outlet nodes of the
conduit (i.e., right click on the conduit and select Reverse from the popup menu
that appears). Adverse slopes are permitted under Dynamic Wave routing. ERROR 117: no cross section defined for Link xxx.
Cross section geometry was never defined for the specified link. ERROR 119: invalid cross section for Link xxx.
Either an invalid shape or invalid set of dimensions was specified for a link’s
cross section. ERROR 121: missing or invalid pump curve assigned to Pump xxx.
Either no pump curve or an invalid type of curve was specified for a pump. ERROR 131: the following links form cyclic loops in the drainage system.
The Steady and Kinematic Wave flow routing methods cannot be applied to
systems where a cyclic loop exists (i.e., a directed path along a set of links that
begins and ends at the same node). Most often the cyclic nature of the loop can
be eliminated by reversing the direction of one of its links (i.e., switching the inlet
and outlet nodes of the link). The names of the links that form the loop will be
listed following this message. ERROR 133: Node xxx has more than one outlet link.
Under Steady and Kinematic Wave flow routing, a junction node can have only a
single outlet link. ERROR 134: Node xxx has illegal DUMMY link connections.
Only a single conduit with a DUMMY cross-section or Ideal-type pump can be
directed out of a node; a node with an outgoing Dummy conduit or Ideal pump
cannot have all of its incoming links be Dummy conduits and Ideal pumps; a
Dummy conduit cannot have its upstream end connected to a storage node. ERROR 135: Divider xxx does not have two outlet links.
Flow divider nodes must have two outlet links connected to them. ERROR 136: Divider xxx has invalid diversion link.
The link specified as being the one carrying the diverted flow from a flow divider
node was defined with a different inlet node. ERROR 137: Weir Divider xxx has invalid parameters.
The parameters of a Weir-type divider node either are non-positive numbers or
are inconsistent (i.e., the value of the discharge coefficient times the weir height
raised to the 3/2 power must be greater than the minimum flow parameter). ERROR 138: Node xxx has initial depth greater than maximum depth.
Self-explanatory. ERROR 139: Regulator xxx is the outlet of a non-storage node.
Under Steady or Kinematic Wave flow routing, orifices, weirs, and outlet links can
only be used as outflow links from storage nodes. ERROR 141: Outfall xxx has more than 1 inlet link or an outlet link.
An outfall node is only permitted to have one link attached to it. ERROR 143: Regulator xxx has invalid cross-section shape.
An orifice must have either a CIRCULAR or RECT_CLOSED shape, while a weir
must have either a RECT_OPEN, TRAPEZOIDAL, or TRIANGULAR shape. ERROR 145: Drainage system has no acceptable outlet nodes.
Under Dynamic Wave flow routing, there must be at least one node designated
as an outfall. ERROR 151: a Unit Hydrograph in set xxx has invalid time base.
The time base of a Unit Hydrograph cannot be negative and if positive, must not
be less than the recording interval for its rain gage. ERROR 153: a Unit Hydrograph in set xxx has invalid response ratios.
The response ratios for a set of Unit Hydrographs (the short-, medium-, and long-
term response hydrographs) must be between 0 and 1.0 and cannot add up to a
value greater than 1.0 ERROR 155: invalid sewer area for RDII at Node xxx.
The sewer area contributing RDII inflow to a node cannot be a negative number. ERROR 156 : inconsistent data file name for Rain Gage xxx.
If two Rain Gages use files for their data sources and have the same Station IDs
then they must also use the same data files. ERROR 157: inconsistent rainfall format for Rain Gage xxx.
If two or more rain gages use the same Time Series for their rainfall data then
they must all use the same data format (intensity, volume, or cumulative volume). ERROR 158 : time series for Rain Gage xxx is also used by another object.
A rainfall Time Series associated with a Rain Gage cannot be used by another
object that is not also a Rain Gage. ERROR 159 : recording interval greater than time series interval for Rain Gage xxx.
The recording time interval specified for the rain gage is greater than the smallest
time interval between values in the Time Series used by the gage. ERROR 161: cyclic dependency in treatment functions at Node xxx.
An example would be where the removal of pollutant 1 is defined as a function of
the removal of pollutant 2 while the removal of pollutant 2 is defined as a function
of the removal of pollutant 1. ERROR 171: Curve xxx has invalid or out of sequence data.
The X-values of a curve object must be entered in increasing order. ERROR 173: Time Series xxx has its data out of sequence.
The time (or date/time) values of a time series must be entered in sequential
order. ERROR 1 81 : invalid Snow Melt Climatology parameters.
The ATI Weight or Negative Melt Ratio parameters are not between 0 and 1 or
the site latitude is not between -60 and +60 degrees. ERROR 1 82 : invalid parameters for Snow Pack xxx.
A snow pack’s minimum melt coefficient is greater than its maximum coefficient;
the fractions of free water capacity or impervious plowable area are not between
0 and 1; or the snow removal fractions sum to more than 1.0. ERROR 183: no type specified for LID xxx.
A named LID control has layers defined for it but its LID type was never
specified. ERROR 184: missing layer for LID xxx.
A required design layer is missing for the specified LID control. ERROR 185: invalid parameter value for LID xxx.
An invalid value was supplied for an LID control’s design parameter. ERROR 187: LID area exceeds total area for Subcatchment xxx.
The area of the LID controls placed within the subcatchment is greater than that
of the subcatchment itself. ERROR 188: LID capture area exceeds total impervious area for Subcatchment xxx.
The amount of impervious area assigned to be treated by LID controls in the
subcatchment exceeds the total amount of impervious area available. ERROR 191: simulation start date comes after ending date.
Self-explanatory. ERROR 193: report start date comes after ending date.
Self-explanatory. ERROR 195: reporting time step is less than routing time step.
Self-explanatory. ERROR 200: one or more errors in input file.
This message appears when one or more input file parsing errors (the 200-series
errors) occur. ERROR 201: too many characters in input line.
A line in the input file cannot exceed 1024 characters. ERROR 203: too few items at line n of input file.
Not enough data items were supplied on a line of the input file. ERROR 205: invalid keyword at line n of input file.
An unrecognized keyword was encountered when parsing a line of the input file. ERROR 207: duplicate ID name at line n of input file.
An ID name used for an object was already assigned to an object of the same
category. ERROR 209: undefined object xxx at line n of input file.
A reference was made to an object that was never defined. An example would be
if node 123 were designated as the outlet point of a subcatchment, yet no such
node was ever defined in the study area. ERROR 211: invalid number xxx at line n of input file.
Either a string value was encountered where a numerical value was expected or
an invalid number (e.g., a negative value) was supplied. ERROR 213: invalid date/time xxx at line n of input file.
An invalid format for a date or time was encountered. Dates must be entered as
month/day/year and times as either decimal hours or as hour:minute:second. ERROR 217: control rule clause out of sequence at line n of input file.
Errors of this nature can occur when the format for writing control rules is not
followed correctly (see Section C.3). ERROR 219: data provided for unidentified transect at line n of input file.
A GR line with Station-Elevation data was encountered in the [TRANSECTS]
section of the input file after an NC line but before any X1 line that contains the
transect’s ID name. ERROR 221: transect station out of sequence at line n of input file.
The station distances specified for the transect of an irregular cross section must
be in increasing numerical order starting from the left bank. ERROR 223: Transect xxx has too few stations.
A transect for an irregular cross section must have at least 2 stations defined for
it. ERROR 225: Transect xxx has too many stations.
A transect cannot have more than 1500 stations defined for it. ERROR 227: Transect xxx has no Manning’s N.
No Manning’s N was specified for a transect (i.e., there was no NC line in the
[TRANSECTS] section of the input file. ERROR 229: Transect xxx has invalid overbank locations.
The distance values specified for either the left or right overbank locations of a
transect do not match any of the distances listed for the transect’s stations. ERROR 231: Transect xxx has no depth.
All of the stations for a transect were assigned the same elevation. ERROR 233: invalid treatment function expression at line n of input file.
A treatment function supplied for a pollutant at a specific node is either not a
correctly formed mathematical expression or refers to unknown pollutants,
process variables, or math functions. ERROR 301: files share same names.
The input, report, and binary output files specified on the command line cannot
have the same names. ERROR 303: cannot open input file.
The input file either does not exist or cannot be opened (e.g., it might be in use
by another program). ERROR 305: cannot open report file.
The report file cannot be opened (e.g., it might reside in a directory to which the
user does not have write privileges). ERROR 307: cannot open binary results file.
The binary output file cannot be opened (e.g., it might reside in a directory to
which the user does not have write privileges). ERROR 309: error writing to binary results file.
There was an error in trying to write results to the binary output file (e.g., the disk
might be full or the file size exceeds the limit imposed by the operating system). ERROR 311: error reading from binary results file.
The command line version of SWMM could not read results saved to the binary
output file when writing results to the report file. ERROR 313: cannot open scratch rainfall interface file.
SWMM could not open the temporary file it uses to collate data together from
external rainfall files. ERROR 315: cannot open rainfall interface file xxx.
SWMM could not open the specified rainfall interface file, possibly because it
does not exist or because the user does not have write privileges to its directory. ERROR 317: cannot open rainfall data file xxx.
An external rainfall data file could not be opened, most likely because it does not
exist. ERROR 318: date out of sequence in rainfall data file xxx.
An external user-prepared rainfall data file must have its entries appear in
chronological order. The first out-of-order entry will be listed. ERROR 319: unknown format for rainfall data file.
SWMM could not recognize the format used for a designated rainfall data file. ERROR 3 20 : invalid format for rainfall interface file.
SWMM was trying to read data from a designated rainfall interface file with the
wrong format (i.e., it may have been created for some other project or actually be
some other type of file). ERROR 321: no data in rainfall interface file for gage xxx.
This message occurs when a project wants to use a previously saved rainfall
interface file, but cannot find any data for one of its rain gages in the interface
file. I t can also occur if the gage uses data from a user-prepared rainfall file and
the station id entered for the gage cannot be found in the file. ERROR 323: cannot open runoff interface file xxx.
A runoff interface file could not be opened, possibly because it does not exist or
because the user does not have write privileges to its directory. ERROR 325: incompatible data found in runoff interface file.
SWMM was trying to read data from a designated runoff interface file with the
wrong format (i.e., it may have been created for some other project or actually be
some other type of file). ERROR 327: attempting to read beyond end of runoff interface file.
This error can occur when a previously saved runoff interface file is being used in
a simulation with a longer duration than the one that created the interface file. ERROR 329: error in reading from runoff interface file.
A format error was encountered while trying to read data from a previously saved
runoff interface file. ERROR 331: cannot open hot start interface file xxx.
A hot start interface file could not be opened, possibly because it does not exist
or because the user does not have write privileges to its directory. ERROR 333: incompatible data found in hot start interface file.
SWMM was trying to read data from a designated hot start interface file with the
wrong format (i.e., it may have been created for some other project or actually be
some other type of file). ERROR 335: error in reading from hot start interface file.
A format error was encountered while trying to read data from a previously saved
hot start interface file. ERROR 336: no climate file specified for evaporation and/or wind speed.
This error occurs when the user specifies that evaporation or wind speed data
will be read from an external climate file, but no name is supplied for the file. ERROR 337: cannot open climate file xxx.
An external climate data file could not be opened, most likely because it does not
exist. ERROR 338: error in reading from climate file xxx.
SWMM was trying to read data from an external climate file with the wrong
format. ERROR 339: attempt to read beyond end of climate file xxx.
The specified external climate does not include data for the period of time being
simulated. ERROR 341: cannot open scratch RDII interface file.
SWMM could not open the temporary file it uses to store RDII flow data. ERROR 343: cannot open RDII interface file xxx.
An RDII interface file could not be opened, possibly because it does not exist or
because the user does not have write privileges to its directory. ERROR 345: invalid format for RDII interface file.
SWMM was trying to read data from a designated RDII interface file with the
wrong format (i.e., it may have been created for some other project or actually be
some other type of file). ERROR 351: cannot open routing interface file xxx.
A routing interface file could not be opened, possibly because it does not exist or
because the user does not have write privileges to its directory. ERROR 353: invalid format for routing interface file xxx.
SWMM was trying to read data from a designated routing interface file with the
wrong format (i.e., it may have been created for some other project or actually be
some other type of file). ERROR 355: mismatched names in routing interface file xxx.
The names of pollutants found in a designated routing interface file do not match
the names used in the current project. ERROR 357: inflows and outflows interface files have same name.
In cases where a run uses one routing interface file to provide inflows for a set of
locations and another to save outflow results, the two files cannot both have the
same name. ERROR 3 61 : could not open external file used for Time Series xxx.
The external file used to provide data for the named time series could not be
opened, most likely because it does not exist. ERROR 3 63 : invalid data in external file used for used for Time Series xxx.
The external file used to provide data for the named time series has one or more
lines with the wrong format. WARNING 01: wet weather time step reduced to recording interval for Rain Gage xxx.
The wet weather time step was automatically reduced so that no period with
rainfall would be skipped during a simulation. WARNING 02: maximum depth increased for Node xxx.
The maximum depth for the node was automatically increased to match the top
of the highest connecting conduit. WARNING 03: negative offset ignored for Link xxx.
The link’s stipulated offset was below the connecting node’s invert so its actual
offset was set to 0. WARNING 04: minimum elevation drop used for Conduit xxx.
The elevation drop between the end nodes of the conduit was below 0.001 ft
(0.00035 m) so the latter value was used instead to calculate its slope. WARNING 05: minimum slope used for Conduit xxx.
The conduit’s computed slope was below the user-specified Minimum Conduit
Slope so the latter value was used instead. WARNING 06: dry weather time step increased to wet weather time step.
The user-specified time step for computing runoff during dry weather periods was
lower than that set for wet weather periods and was automatically increased to
the wet weather value. WARNING 07: routing time step reduced to wet weather time step.
The user-specified time step for flow routing was larger than the wet weather
runoff time step and was automatically reduced to the runoff time step to prevent
loss of accuracy. WARNING 08: elevation drop exceeds length for Conduit xxx.
The elevation drop across the ends of a conduit exceeds its length. The program
computes the conduit’s slope as the elevation drop divided by the length instead
of using the more accurate right triangle method. The user should check for
errors in the length and in both the invert elevations and offsets at the conduit’s
upstream and downstream nodes. WARNING 09: time series interval greater than recording interval for Rain Gage xxx.
The smallest time interval between entries in the precipitation time series used by
the rain gage is greater than the recording time interval specified for the gage. If
this was not actually intended then what appear to be continuous periods of
rainfall in the time series will instead be read with time gaps in between them. WARNING 10 : crest elevation is below downstream invert for regulator Link xxx.
The height of the opening on an orifice, weir, or outlet is below the invert
elevation of its downstream node. Users should check to see if the regulator’s
offset height or the downstream node’s invert elevation is in error. WARNING 11 : non-matching attributes in Control Rule xxx.
The premise of a control is comparing two different types of attributes to one
another (for example, conduit flow and junction water depth).

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