General Options in the Run Manager for InfoSWMM and InfoSWMM Hydraulics and Hydrology

General Options in the Run Manger for InfoSWMM and InfoSWMM Hydraulics and Hydrology

The General page of the Simulation Options dialog, shown below, sets values for the following options. In InfoSWMM v14.5 and above each tab is shown in two rows

Contents of this simulation option dialog page are described below.

Name Description
Flow Units Six choices of flow units are available. Selecting a US flow unit (i.e., CFS, GPM, or MGD) means that all other Units of Measurement will be expressed in US units, while choosing a metric flow unit (i.e., CMS, LPS, or MLD) will force all quantities to be expressed in metric units.InfoSWMM H2OMap SWMM InfoSWMM SA will automatically change the units of all other quantities in the model, however, it must be noted that the model does not recalculate/re-adjust the values of the previously entered data. It only changes the units. Therefore, it is very essential to choose the appropriate flow unit before editing InfoSWMM inputs.
Process Models One or more of the process models may be excluded from the simulation. For example, if the main interest is to conduct rainfall-runoff simulation, other inflow sources such as dry weather flow, external inflow, ground water flow contribution, or RDII flow may be ignored during the analysis. By doing so, fluctuations in later inflow that may be exhibited during dry periods may be avoided thus improving computational efficiency. The added benefit of ignoring an inflow source is that one may develop different model scenarios each simulating the effect of one or more inflow sources on the system. This may help in analyzing the relative contribution of the various sources (e.g. RDII) to a point of interest such as treatment plants.
Infiltration Model This option controls how infiltration of rainfall into the upper soil zone of Subcatchments is modeled. The choices are: Horton, Green-Ampt, and Curve Number. Each soil definition has a place to define parameters appropriate for each infiltration method. This parameter is the default for each Subcatchment but the Attribute Browser can be used to change the infiltration method for specific Subcatchments if needed.


Routing Model This option determines which method is used to route flows through the conveyance system. The choices are:

  • Steady Flow - 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.
  • Kinematic Wave - Kinematic Wave Routing solves the continuity equation along with a simplified form of the momentum equation in each conduit. The latter requires that the slope of the water surface equal that of the conduit invert. 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.
  • Dynamic Wave - Dynamic Wave Routing solves the complete St. Venant flow equations and therefore produces the most accurate results. These equations consist of the continuity and momentum equations for conduits and a flow continuity equation at nodes. 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 minute or less.

Runoff Model This option allows users to choose the method to use for modeling surface runoff. The choices are: EPA SWMM (Non-linear Reservoir), the Colorado Urban Hydrograph Procedure (CUHP), NRCS Dimensionless Unit Hydrograph, NRCS Triangular Unit Hydrograph, Delmarva Unit Hydrograph, Snyder Unit Hydrograph, Clark Unit Hydrograph, Espey Unit Hydrograph, the Santa Barbara Unit Hydrograph Method, Rational Method and the San Diego Modified Rational Formula.

InfoSWMM H2OMap SWMM InfoSWMM SA offers eleven choices for modeling surface runoff (Figure 1 shows how to use the hydrology options in the Run Manager):

1. EPA SWMM5 Nonlinear Reservoir

2. The Colorado Urban Hydrograph Procedure (CUHP)

3. NRCS (SCS) Dimensionless Unit Hydrograph Method

4. NRCS (SCS) Triangular Unit Hydrograph Method

5. Delmarva Unit Hydrograph (SCS)

6. Snyder Unit Hydrograph Method (HEC-RAS)

7. Clark Unit Hydrograph Method (HEC-RAS)

8. Espey Unit Hydrograph Method (Texas)

9. Santa Barbara Urban Hydrograph Method (California)

10. San Diego Modified Rational Formula (Rational Method)

11. Modified Rational Formula (Rational Method)

12. German Storm Hydrology (German Runoff)

13. Laurenson Hydrology

The choices range from EPA SWMM (1), Local to Colorado (2), Curve Number (options 3.4.5), HEC-RAS (options 7 ,8), Local to Texas (8), Local to California (9) and Rational Methods (10,11), German Hydrology (12) and XPRAFTS or Laurenson Hydrology (13).

6-hour Precipitation Depth Used only for the San Diego modified rational formula surface runoff model.
Allow Ponding Selecting 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.
Min. Conduit Slope Often times conduits with very small slopes can cause numerical instability during an InfoSWMM H2OMap SWMM InfoSWMM SA model simulation. To increase numerical stability, a minimum conduit slope can be specified. This adjustment applies to all three Routing Models.
Temporary Directory Specify the name of a file directory (or folder) where InfoSWMM H2OMap SWMM InfoSWMM SA 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 root directory of the current drive.

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