The Junction inlet data table stores information regarding the inlet at the junction node. Refer to the section on inflow editor for more information on these input data. The following table shows the whole first row of the DB Table on separate rows in the image.
Field  Description 
Junction ID  Name assigned to the junction. 
Overland Junction  Name of the Overland Junction that is the source of the flow to the Inlet 
Inlet Type  One of five types of Inlets (1) Continuous Grate, (2) Continuous CurbOpening, (3) Sag Continuous Grate, (4) Sag Continuous CurbOpening and (5) Sag Combination 
Cross Slope  Cross slope (Sx) or the road cross slope 
Grate Width  Width of grate in feet or meters 
Grate Length  Length of grate (L) in feet or meters 
Splash Velocity  Velocity where splashover first occurs (V0) in feet/second or meters/second 
Open Height  Height of the Curb Opening in feet or meters 
Open Length  Length of the Curb Opening in feet or meters 
Gutter Depression  Gutter Depression in feet or meters 
Depression Width  Lateral width of the gutter depression in feet or meters 
Clear Area  Clear opening area of grate (Ag) 
Threshold Depth  Depth up to which gate behaves as weir or the Threshold Depth in feet or meters 
The parameters for a Sag CurbOpening Inlet are:
The parameters for a Sag Grate Inlet are:
The parameters for a Sag Combination Inlet are:
The parameters for a Continuous Grate Inlet are:
The parameters for a Continuous Curb Opening Inlet are:
To model a depressed inlet, values for the following parameters are also required:
The dialog box for grate inlet on grade is shown below.
· Flow Unit – Select the desired flow unit.
· Location – On grade and in sag.
· Solving Target – Efficiency or length.
· Manning’s Coefficient – Manning’s roughness coefficient for the gutter.
· Slope – Longitudinal slope of the street.
· Discharge – Flow rate through the gutter.
· Gutter Width –Width of the gutter measured from the curb.
· Gutter Cross Slope – Slope of the gutter measured perpendicular to centerline of the street.
· Road Cross Slope –Slope of the street perpendicular to the longitudinal direction.
· Grate Type – Select one of the eight grate types listed.
· Efficiency –Interception efficiency of the grate. It represents ratio of intercepted flow to total gutter flow.
· Grate Width – Width of the grate.
· Grate Length – Length of the grate.
· Clogging – Percentage of the grate opening that is clogged by debris, leaves, etc, and is not available to intercept flow.
· Flow Area – Wetted area of the gutter.
· Depth – Flow depth in the gutter.
· Gutter Depression – Local depression of the gutter measured from the point the cross slope line intersects with the curb.
· Velocity – Flow velocity through the gutter.
· Total Depression – Sum of the local depression and the gutter depression.
· Intercepted Flow – The portion of gutter flow that entered the inlet.
· Bypass Flow – The portion of the gutter flow that is not intercepted by the inlet. It is total gutter flow less the intercepted flow.
· Splash Over Velocity – Velocity where splash over first occurs. Splash over refers to the fraction of frontal gutter flow that is not intercepted by the inlet.
· Frontal Flow Factor – The ratio of intercepted frontal flow to total frontal flow.
· Side Flow Factor – The ratio of intercepted side flow to total side flow.
· Grate Flow Ratio – The ratio of frontal flow to total gutter flow.
· Active Grate Length – Portion of grate length (the side that is parallel to the curb) that is not clogged.
· Spread – Top width, or width of the gutter at the water surface elevation.
The dialog box for curbopening inlet on grade is shown below. For methodology click here.
· Flow Unit – Select the desired flow unit.
· Location – On grade and in sag.
· Solving Target – Efficiency or length.
· Manning’s Coefficient – Manning’s roughness coefficient for the gutter.
· Slope – Longitudinal slope of the street.
· Discharge – Flow rate through the gutter.
· Gutter Width –Width of the gutter measured from the curb.
· Gutter Cross Slope – Slope of the gutter measured perpendicular to centerline of the street.
· Road Cross Slope –Slope of the street perpendicular to the longitudinal direction.
· Efficiency –Interception efficiency of the inlet. It represents ratio of intercepted flow to total gutter flow. It is an output if selected as a solving target.
· Curb Opening Length – Length of the curbopening inlet (i.e., length parallel to the curb).
· Local Depression – Depth of local depression of the gutter measured from the point where the cross slope line intersects with the curb.
· Local Depression Width – Width of the local depression.
· Flow Area – Wetted area of the gutter.
· Depth – Flow depth in the gutter.
· Gutter Depression – Local depression of the gutter measured from the point the cross slope line intersects with the curb.
· Velocity – Flow velocity through the gutter.
· Total Depression – Sum of the local depression and the gutter depression.
· Intercepted Flow – The portion of gutter flow that entered the inlet.
· Bypass Flow – The portion of the gutter flow that is not intercepted by the inlet. It is total gutter flow less the intercepted flow.
· Equivalent Cross Slope – An equivalent crossslope that has a conveyance capacity equal to that of the compound crossslope.
· Spread – Top width, or width of the gutter at the water surface elevation.
· Total Interception Length – Length of the curb required to intercept 100% of the gutter flow.
· Length Factor – Ratio of actual curb length to total interception length.
The dialog box for combination inlet on grade is shown below. For methodology click here.
· Flow Unit – Select the desired flow unit.
· Location – On grade and in sag.
· Solving Target – Efficiency, equal opening lengths, or curb opening length.
· Manning’s Coefficient – Manning’s roughness coefficient for the gutter.
· Slope – Longitudinal slope of the street.
· Discharge – Flow rate through the gutter.
· Gutter Width –Width of the gutter measured from the curb.
· Gutter Cross Slope – Slope of the gutter measured perpendicular to centerline of the street.
· Road Cross Slope –Slope of the street perpendicular to the longitudinal direction.
· Grate Type – Select one of the eight grate types listed.
· Efficiency –Interception efficiency of the inlet. It represents ratio of intercepted flow to total gutter flow. It is an output if selected as a solving target.
· Grate Width – Width of the grate.
· Grate Length – Length of the grate.
· Clogging – Percentage of the grate opening that is clogged by debris, leaves, etc, and is not available to intercept flow.
· Curb Opening Length – Length of the curbopening inlet (i.e., length parallel to the curb).
· Local Depression – Depth of local depression of the gutter measured from the point where the cross slope line intersects with the curb.
· Local Depression Width – Width of the local depression.
· Flow Area – Wetted area of the gutter.
· Depth – Flow depth in the gutter.
· Gutter Depression – Local depression of the gutter measured from the point the cross slope line intersects with the curb.
· Velocity – Flow velocity through the gutter.
· Total Depression – Sum of the local depression and the gutter depression.
· Intercepted Flow – The portion of gutter flow that entered the inlet.
· Bypass Flow – The portion of the gutter flow that is not intercepted by the inlet. It is total gutter flow less the intercepted flow.
· Splash Over Velocity – Velocity where splash over first occurs. Splash over refers to the fraction of frontal gutter flow that is not intercepted by the inlet.
· Frontal Flow Factor – The ratio of intercepted frontal flow to total frontal flow.
· Side Flow Factor – The ratio of intercepted side flow to total side flow.
· Grate Flow Ratio – The ratio of frontal flow to total gutter flow.
· Active Grate Length – Portion of grate length (the side that is parallel to the curb) that is not clogged.
· Equivalent Cross Slope – An equivalent crossslope that has a conveyance capacity equal to that of the compound crossslope.
· Spread – Top width, or width of the gutter at the water surface elevation.
· Total Interception Length – Length of the curb required to intercept 100% of the gutter flow.
· Length Factor – Ratio of actual curb length to total interception length.
The dialog box for slotted inlet on grade is shown below. For methodology click here.
· Flow Unit – Select the desired flow unit.
· Locations – On grade and in sag.
· Solving Target – Efficiency and length.
· Manning’s Coefficient – Manning’s roughness coefficient for the gutter.
· Slope – Longitudinal slope of the street.
· Discharge – Flow rate through the gutter.
· Gutter Width –Width of the gutter measured from the curb.
· Gutter Cross Slope – Slope of the gutter measured perpendicular to centerline of the street.
· Road Cross Slope –Slope of the street perpendicular to the longitudinal direction.
· Efficiency –Interception efficiency of the inlet. It represents ratio of intercepted flow to total gutter flow. It is an output if selected as a solving target.
· Slot Length – Length of the inlet.
· Local Depression – Depth of local depression of the gutter measured from the point where the cross slope line intersects with the curb.
· Local Depression Width – Width of the local depression.
· Flow Area – Wetted area of the gutter.
· Depth – Flow depth in the gutter.
· Gutter Depression – Local depression of the gutter measured from the point the cross slope line intersects with the curb.
· Velocity – Flow velocity through the gutter.
· Total Depression – Sum of the local depression and the gutter depression.
· Intercepted Flow – The portion of gutter flow that entered the inlet.
· Bypass Flow – The portion of the gutter flow that is not intercepted by the inlet. It is total gutter flow less the intercepted flow.
· Equivalent Cross Slope – An equivalent crossslope that has a conveyance capacity equal to that of the compound crossslope.
· Spread – Top width, or width of the gutter at the water surface elevation.
· Total Interception Length – Length of the curb required to intercept 100% of the gutter flow.
· Length Factor – Ratio of actual curb length to total interception length.
The dialog box for ditch inlets on grade is shown below. For methodology click here.
· Flow Unit – Select the desired flow unit.
· Locations – On grade and in sag.
· Solving Target – Efficiency and length.
· Manning’s Coefficient – Manning’s roughness coefficient for the gutter.
· Slope – Longitudinal slope of the street.
· Discharge – Flow rate through the gutter.
· Bottom Width – Bottom width of the ditch (channel).
· Left Side Slope – Left side slope of the ditch.
· Right Side Slope – Right side of the ditch.
· Grate Type – Select one of the eight grate types listed.
· Efficiency –Interception efficiency of the grate. It represents ratio of intercepted flow to total gutter flow.
· Grate Width – Width of the grate.
· Grate Length – Length of the grate.
· Clogging – Percentage of the grate opening that is clogged by debris, leaves, etc, and is not available to intercept flow.
· Flow Area – Wetted area of the gutter.
· Depth – Flow depth in the gutter.
· Velocity – Flow velocity through the gutter.
· Intercepted Flow – The portion of gutter flow that entered the inlet.
· Bypass Flow – The portion of the gutter flow that is not intercepted by the inlet. It is total gutter flow less the intercepted flow.
· Splash Over Velocity – Velocity where splash over first occurs. Splash over refers to the fraction of frontal gutter flow that is not intercepted by the inlet.
· Frontal Flow Factor – The ratio of intercepted frontal flow to total frontal flow.
· Side Flow Factor – The ratio of intercepted side flow to total side flow.
· Grate Flow Ratio – The ratio of frontal flow to total gutter flow.
· Active Grate Length – Portion of grate length (the side that is parallel to the curb) that is not clogged.
· Spread – Top width, or width of the gutter at the water surface elevation.
· Velocity Head – Energy head due to velocity.
· Critical Depth – Depth corresponding to minimum specific energy of the channel.
· Critical Slope – Channel slope under critical depth.
· Specific Energy – Sum of velocity head and pressure head.
· Froude Number – Flow characteristics dimensionless parameter for the ditch.
The dialog box for combination inlet in sag is shown below. For methodology click here.
· Flow Unit – Select the desired flow unit.
· Location – On grade and in sag.
· Solving Target – Efficiency, equal opening lengths, or curb opening length.
· Discharge – Flow rate through the gutter.
· Gutter Width – Width of the gutter measured from the curb to the break in slope of the street.
· Gutter Cross Slope – Slope of the gutter measured perpendicular to centerline of the street.
· Road Cross Slope –Slope of the street perpendicular to the longitudinal direction.
· Spread – Top width, or width of the gutter at the water surface elevation. Could be an output if selected as a solving target.
· Grate Type – Select one of the eight grate types listed.
· Throat Incline Angle – Angle of the curb opening throat.
· Grate Width – Width of the grate.
· Grate Length – Length of the grate.
· Clogging – Percentage of the grate opening that is clogged by debris, leaves, etc, and is not available to intercept flow.
· Curb Opening Length – Length of the curbopening inlet (i.e., length parallel to the curb).
· Local Depression – Depth of local depression of the gutter measured from the point where the cross slope line intersects with the curb.
· Local Depression Width – Width of the local depression.
· Curb Throat Type – Horizontal, vertical, or incline.
· Curb Height – Height of the curb.
· Open Grate Area – Clear area of the grate accounting for clogging, and area occupied by the bars depending on the grate type. Used when the grate acts as an orifice.
· Depth – Flow depth in the gutter.
· Gutter Depression – Local depression of the gutter measured from the point the cross slope line intersects with the curb.
· Total Depression – Sum of the local depression and the gutter depression (measured from the point where the street cross slope meets the curb).
· Active Grate Weir Length – Portion of grate length and width that is not clogged and not covered by the bars. Used when the grate acts as a weir.
Innovyze, a leading global innovator of business analytics software and technologies for smart wet infrastructure, today announced the planned retirement of the H_{2}OMAP Modeling Platform, as well as a new path for existing customers to easily adapt the more powerful next generation programs, InfoWater, InfoSewer and InfoSWMM.
H_{2}OMAP was the first GISbased hydraulic modeling package available in the industry. It helped pioneer the shift from CAD based lines and attributes to database driven maps. The platform has served the industry well for nearly two decades. About 4 years after the creation of H_{2}OMAP products, Innovyze developed an additional approach with new products that sit as an extension in Esri’s ArcMAP (ArcGIS) software. The innovation of new tools grew rapidly in the InfoWater, InfoSWMM, and InfoSewer products but several of these advancements could not be adopted in the limited platform of the H_{2}OMAP products.
“Many of us love the platform that we were trained to model in but we have decided to finally discontinue support for our H_{2}OMAP products,” said Product Manager, Brett Singley, P.E. “We are confident that our assisted transition to the Info products will be easy and much more helpful to our valued clients.” The following detail some of the value that previous H_{2}OMAP users have found in the new platform:
For more information on the many innovations that have been added to the GISbased modeling tools, please contact Innovyze directly for a demonstration or discussion.
Mr. Singley adds, “We value our customers because we know it is you that have helped us innovate and inspired us to keep making these tools. We have provided a path for all existing H_{2}OMAP users to upgrade their existing licenses to the newer platform. Your Client Service Manager can discuss with you the best options for moving forward. Both Esri ArcGIS and Stand Alone versions of the Info products are available to provide you with the most innovative, GISbased decisionsupport tool in our industry.”
About Innovyze
Innovyze is the global leader in smart water data analytics that continues to shape the water resources engineering industry with exceptional modeling, design and realtime monitoring software solutions. Its clients include the majority of the largest UK, Australasian, East Asian and North American cities, foremost utilities on all five continents, and ENR toprated design firms. Backed by unparalleled expertise and offices in North America, Europe, and Asia Pacific, the Innovyze connected portfolio of bestinclass product lines empowers thousands of engineers to competitively plan, manage, design, protect, operate, and sustain highly efficient and resilient infrastructure systems, and provides an enduring platform for customer success. For more information, call Innovyze at +18885545022, or visit http://www.innovyze.com.
The objective of the optimal calibration problem is to minimize the numerical discrepancy between the observed and predicted values of link flow, link depth, and/or link velocity at various locations in the system. Any of the following five different mathematical objective functions can be used in InfoSWMM && InfoSWMM SA Calibrator.
Root Mean Square Error (RMSE)
In the ideal condition when corresponding observed and simulated values exactly match, value of RMSE will be zero.
Simple Least Square Error (SLSE)
This performance evaluation function could assume values ranging from zero (best fit) to ∞ (poor fit), and it tends to favor large errors and large (i.e., peak) flows.
Mean Simple Least Square Error (MSLSE)
This performance evaluation function could assume values ranging from zero (best fit) to ∞ (poor fit), and it tends to favor large errors and large (i.e., peak) flows.
Difference in Total Volume
Difference in total volume could range from ∞ (poor performance) to ∞ (poor performance), the ideal value being zero (i.e., exact match between total simulated volume and total observed volume).
NashSutcliffe Efficiency Criterion
This efficiency criterion could assume values from ∞ (poor performance) to 1 (perfect model).
RSquare (R2)
R2 value varies from zero (indicates worst fit) to unity (indicates perfect fit).
Modified Coefficient of Efficiency
The modified coefficient of efficiency could assume values from ∞ (poor performance) to 1 (perfect model).
Dimensionless Root Mean Square Error (DRMSE)
In the ideal condition when corresponding observed and
Dimensionless Simple Least Square Error (DSLSE)
Simulated values exactly match, value of DRMSE will be zero.
This performance evaluation function could assume values ranging from zero (best fit) to ∞ (poor fit), and it tends to be independent of length of records and it favor large errors and large (i.e., peak) flows.
where N designates the total number of measurements available, Pobsi represents the observed measurement values at time i; Psimi is the model simulated values at time i;Pobs is mean of the measured values; Psim is the mean of the simulated values.
It is believed that complete assessment of model performance should include at least one relative error measure (e.g., modified coefficient of efficiency) and at least one absolute error measure (e.g., root mean square error) with additional supporting information (e.g., a comparison between the observed and simulated mean and standard deviation)2.
The number of field measurements defining the objective function must be greater than or equal to the number of calibration variables. It is expected that the accuracy of the model calibration would be increased by the use of a large number of field measurements. The decision variables could be any one or more of about fifty nfoSWMM && InfoSWMM SA parameters. These decision variables are automatically adjusted to minimize the objective function selected while satisfying a set of implicit and explicit constraints.
Genetic algorithms (GA) are an adaptation procedure based on the mechanics of natural genetics and natural selection1. They are designed to perform search procedures of an artificial system by emulating the evolution process (Darwin’s evolution principle) observed in nature and biological organisms. The evolution process is based on the preferential survival and reproduction of the fittest member of a population with direct inheritance of genetic information from parents to offspring and the occasional mutation of genes. The principal advantages of genetic algorithms are their ability to converge expeditiously on an optimal or nearoptimal solution without having to analyze all possible solutions available and without requiring derivatives or other auxiliary knowledge.
2.1 OVERVIEW OF GENETIC ALGORITHMS
Genetic algorithms are fundamentally different from traditional optimization methods in terms of the search process. While traditional routines track only a single pathway to the optimal solution, genetic algorithms search from an entire population of possible solutions (individuals). In addition, genetic algorithms use randomized and localized operators as opposed to deterministic rules. Each individual in the population is represented by either a string or a set of real numbers encoding one possible solution. The performance of each individual in the population is measured by its fitness (goodness), which quantifies the degree of optimality of the solution. Based on their fitness values, individuals are selected for reproduction of the next generation. Each new generation maintains its original size. The selected individuals reproduce their offspring by mimicking gene operations of crossover and mutation. After a number of generations, the population is expected to evolve artificially, and the optimal or near optimal solution is ultimately reached.
2.2 COMPONENTS OF GENETIC ALGORITHMS
Standard genetic algorithms involve three basic functions: selection, crossover, and mutation. Each function is briefly described below.
Selection – Individuals in a population are selected for reproduction according to their fitness values. In biology, fitness is the number of offspring that survive to reproduction. Given a population consisting of individuals identified by their chromosomes, selecting two chromosomes to represent parents to reproduce offspring is guided by a probability rule that the higher the fitness an individual has, the more likely the individual will survive. There are many selection methods available including weighted roulette wheel, sorting schemes, proportionate reproduction, and tournament selection.
Crossover – Selected parents reproduce the offspring by performing a crossover operation on the chromosomes (cut and splice pieces of one parent to those of another). In nature, crossover implies two parents exchange parts of their corresponding chromosomes. In genetic algorithms, a crossover operation makes two strings swap their partial strings. Since more fit individuals have a higher probability of producing offspring than less fit ones, the new population will possess, on average, an improved fitness level. The basic crossover is a onepoint crossover. Two selected strings create two offspring strings by swapping the partial strings, which is cut by one randomly sampled breakpoint along the chromosome. The onepoint crossover can easily be extended to kpoint crossover. It randomly samples k breakpoints on chromosomes and then exchanges every second corresponding segments of two parent strings.
Mutation – Mutation is an insurance policy against lost genes. It works on the level of string genes by randomly altering gene value. With small probability, it randomly selects one gene on a chromosome then replaces the gene by a randomly selected value. The operation is designed to prevent GA from premature termination namely converging to a solution too early.
Elitism – The selection and crossover operators will tend to ensure that the best genetic material and the components of the fittest chromosomes will be carried forward to the next generation. However, the probabilistic nature of these operators implies that this will not always be the case. An elitist strategy is therefore required to ensure that the best genetic material will not be lost by chance. This is accomplished by always carrying forward the best chromosome from one generation to the next.
The flowchart below illustrates the optimal calibration process.
The successful application of a sewer collection system model to the planning, design, and management of urban stormwater systems is highly dependent upon how well the model is calibrated and how well the model mimics the reality. Model calibration consists of fine tuning of model parameters until the model simulates field conditions to an established degree of accuracy. Finetuning of the model entails making adjustments to the model parameters to obtain the desired output data. The degree of accuracy refers to the difference between simulated and actual values and is used to establish a level of confidence in the model. It is normally expressed as a percent difference (typically [ 10 percent) between model predictions and actual measurements. Calibration is important to establish model credibility, create a benchmark, produce a predictive tool, increase knowledge and understanding of the system and its operations, and to discover errors or unknown conditions in the field.
Periodic recalibration of models is also necessary not only when major new facilities are added to the system or when system operations change, but also to learn more about the system so that informed decisions can be effectively made to improve system operations and performance.
InfoSWMM Calibrator provides a fully automated approach to accurate and efficient stormwater management model calibration. The program makes use of a variation of the genetic algorithm optimization technology enriched with global search control strategies and closely coupled with InfoSWMM for maximum efficiency, performance and reliability.
1 CALIBRATION FORMULATION
When calibrating a stormwater management model, the goal is to determine the best set of InfoSWMM model parameters which produces the lowest overall deviation between the numerically simulated model results and the observed field data at user specified locations in the system. Observed field data can include link flow, link depth, and link velocity measurements. These measurements could be taken at one or more links in the system.
Grouping is very useful in the calibration process. InfoSWMM calibrator has five group types: subcatchment group, soil group, aquifer group, RDII group, and conduit group. Grouping has to be made accounting for similarity in the characteristics of the elements. For example, if the modeler is interested in calibrating subcatchment width s/he may need to group subcatchments depending on their similarity in shape/size so that subcatchments in the group may use the same multiplying factor during the calibration. To calibrate Manning’s roughness parameter for conduits, one may need to group conduits together depending on similarity in their characteristics such as material, date of installation, location, and diameter. It is assumed that all elements within a group will have an identical multiplying factor for the parameter being calibrated. The multiplying factor would be multiplied by the original parameter value assigned to each of the individual elements to determine actual value of parameter to be used during the calibration process.
InfoSWMM Calibrator casts the calibration problem as an implicit nonlinear optimization problem, subject to explicit inequality and equality constraints. It computes optimal model parameters within userspecified bounds, such that the deviation between the model predictions and field measurements is minimized. The optimal model calibration problem is thus governed by an objective function and its associated set of constraints.
1.1 OBJECTIVE FUNCTIONS
The objective of the optimal calibration problem is to minimize the numerical discrepancy between the observed and predicted values of link flow, link depth, and/or link velocity at various locations in the system. Any of the following nine different mathematical objective functions can be used in InfoSWMM Calibrator.
Root Mean Square Error (RMSE)
In the ideal condition when corresponding observed and simulated values exactly match, value of RMSE will be zero.
Simple Least Square Error (SLSE)
This performance evaluation function could assume values ranging from zero (best fit) to ∞ (poor fit), and it tends to favor large errors and large (i.e., peak) flows.
Mean Simple Least Square Error (MSLSE)
This performance evaluation function could assume values ranging from zero (best fit) to ∞ (poor fit), and it tends to favor large errors and large (i.e., peak) flows.
Difference in Total Volume
Difference in total volume could range from ∞ (poor performance) to ∞ (poor performance), the ideal value being zero (i.e., exact match between total simulated volume and total observed volume).
NashSutcliffe Efficiency Criterion
This efficiency criterion could assume values from ∞ (poor performance) to 1 (perfect model).
RSquare (R2)
R2 value varies from zero (indicates worst fit) to unity (indicates perfect fit).
Modified Coefficient of Efficiency
The modified coefficient of efficiency could assume values from ∞ (poor performance) to 1 (perfect model).
Dimensionless Root Mean Square Error (DRMSE)
In the ideal condition when corresponding observed and simulated values exactly match, value of DRMSE will be zero.
Dimensionless Simple Least Square Error (DSLSE)
where N designates the total number of measurements available, Pobsi represents the observed measurement values at time i; Psimi is the model simulated values at time i; is mean of the measured values; is mean of the simulated values.
This performance evaluation function could assume values ranging from zero (best fit) to ∞ (poor fit), and it tends to be independent of length of records and it favor large errors and large (i.e., peak) flows.
It is believed that complete assessment of model performance should include at least one relative error measure (e.g., modified coefficient of efficiency) and at least one absolute error measure (e.g., root mean square error) with additional supporting information (e.g., a comparison between the observed and simulated mean and standard deviation).
The number of field measurements defining the objective function must be greater than or equal to the number of calibration variables. It is expected that the accuracy of the model calibration would be increased by the use of a large number of field measurements. The decision variables could be any one or more of about fifty InfoSWMM parameters. These decision variables are automatically adjusted to minimize the objective function selected while satisfying a set of implicit and explicit constraints.
1.2 IMPLICIT SYSTEM CONSTRAINTS
The implicit constraints on the system correspond to equations that govern/simulate the underlying hydrologic, hydraulic and water quality processes including conservation of mass and conservation of momentum at various scales such as node, and/or link, and/or the entire system. Each function call to InfoSWMM with a set of decision variables returns the simulated values for link flow, link depth, and link velocity that will be compared with corresponding measured data.
1.3 EXPLICIT CONSTRAINTS
The explicit bound constraints are used to set minimum (lower) and maximum (upper) limits on the calibrable InfoSWMM parameters. For example, for each conduit group G (where a single conduit may constitute a group) Manning’s roughness coefficient for a conduit in the group may be bound by an explicit inequality constraint as follows:
where kmin designates the lower bound multiplier (minimum value of a multiplier) for roughness coefficient of conduits in conduit group G; kmax represents the upper bound multiplier (maximum value of a multiplier) for roughness coefficient of conduits in conduit group G; and n is roughness coefficient value for conduit i in group G. Please note that each of the conduits in group G could take different values of n. The only value that is same for all conduits in the group is the multiplier k.
It should be noted that the choice of grouping may greatly affect the calculated parameter values as well as the convergence accuracy. It is also expected that the final calculated parameters, will be close to the actual values (i.e., optimal/near optimal values) although they may not be “exact” or absolute optima.
2 GENETIC ALGORITHMS
Genetic algorithms (GA) are an adaptation procedure based on the mechanics of natural genetics and natural selection1. They are designed to perform search procedures of an artificial system by emulating the evolution process (Darwin’s evolution principle) observed in nature and biological organisms. The evolution process is based on the preferential survival and reproduction of the fittest member of a population with direct inheritance of genetic information from parents to offspring and the occasional mutation of genes. The principal advantages of genetic algorithms are their ability to converge expeditiously on an optimal or nearoptimal solution without having to analyze all possible solutions available and without requiring derivatives or other auxiliary knowledge.
2.1 OVERVIEW OF GENETIC ALGORITHMS
Genetic algorithms are fundamentally different from traditional optimization methods in terms of the search process. While traditional routines track only a single pathway to the optimal solution, genetic algorithms search from an entire population of possible solutions (individuals). In addition, genetic algorithms use randomized and localized operators as opposed to deterministic rules. Each individual in the population is represented by either a string or a set of real numbers encoding one possible solution. The performance of each individual in the population is measured by its fitness (goodness), which quantifies the degree of optimality of the solution. Based on their fitness values, individuals are selected for reproduction of the next generation. Each new generation maintains its original size. The selected individuals reproduce their offspring by mimicking gene operations of crossover and mutation. After a number of generations, the population is expected to evolve artificially, and the optimal or near optimal solution is ultimately reached.
2.2 COMPONENTS OF GENETIC ALGORITHMS
Standard genetic algorithms involve three basic functions: selection, crossover, and mutation. Each function is briefly described below.
Selection – Individuals in a population are selected for reproduction according to their fitness values. In biology, fitness is the number of offspring that survive to reproduction. Given a population consisting of individuals identified by their chromosomes, selecting two chromosomes to represent parents to reproduce offspring is guided by a probability rule that the higher the fitness an individual has, the more likely the individual will survive. There are many selection methods available including weighted roulette wheel, sorting schemes, proportionate reproduction, and tournament selection.
Crossover – Selected parents reproduce the offspring by performing a crossover operation on the chromosomes (cut and splice pieces of one parent to those of another). In nature, crossover implies two parents exchange parts of their corresponding chromosomes. In genetic algorithms, a crossover operation makes two strings swap their partial strings. Since more fit individuals have a higher probability of producing offspring than less fit ones, the new population will possess, on average, an improved fitness level. The basic crossover is a onepoint crossover. Two selected strings create two offspring strings by swapping the partial strings, which is cut by one randomly sampled breakpoint along the chromosome. The onepoint crossover can easily be extended to kpoint crossover. It randomly samples k breakpoints on chromosomes and then exchanges every second corresponding segments of two parent strings.
Mutation – Mutation is an insurance policy against lost genes. It works on the level of string genes by randomly altering gene value. With small probability, it randomly selects one gene on a chromosome then replaces the gene by a randomly selected value. The operation is designed to prevent GA from premature termination namely converging to a solution too early.
Elitism – The selection and crossover operators will tend to ensure that the best genetic material and the components of the fittest chromosomes will be carried forward to the next generation. However, the probabilistic nature of these operators implies that this will not always be the case. An elitist strategy is therefore required to ensure that the best genetic material will not be lost by chance. This is accomplished by always carrying forward the best chromosome from one generation to the next.
The flowchart below illustrates the optimal calibration process.
In InfoWorks ICM 6.5 and later the SWMM 5 LID Controls were added to the Subcatchment Grid of ICM. Here is a copy of the ICM Help File. The LID Controls are entered in the Subcatchment Grid (1), in the SuDS or LID Tab (2), it uses SWMM 5 LID Control Types (3) and has a grid of all of the LID or SuDS data. More here on our Innovyze Blog.
Table 2. All Columns from the Help File from InfoWorks ICM SuDS Table
Help Text  Database Field  Data Type  Size  Units  Precision  Default  Error Lower Limit  Error Upper Limit  Warning Lower Limit  Warning Upper Limit 
Control ID  The name that identifies this control object.  control_id  Text  64  
Control type  The type of SUDS control can be selected from the dropdown list.  control_type  Text  25  Bioretention cell  
Berm height  Storage height.  surf_berm_height  Double  Pipe size  3  0  
Storage depth  Storage depth.  surf_storage_depth  Double  Pipe size  3  0  
Vegetation volume fraction  Fraction of the area above the surface that is filled with vegetation.  surf_veg_vol_fraction  Double  3  0  
Surface roughness (Manning’s n)  Manning’s n for overland flow. This surface roughness cannot be 0 for permeable pavements, green roofs or vegetative swales.  surf_roughness_n  Double  3  0.1  
Surface slope  The gradient of the surface slope.  surf_slope  Double  Gradient  3  0.01  
Swale side slope  The gradient of the slope of side walls.  surf_xslope  Double  Gradient  3  0.05  
Pavement thickness  The thickness of the pavement layer.  pave_thickness  Double  Pipe size  3  100  
Pavement void ratio  The void ratio of the pavement layer.  pave_void_ratio  Double  3  0.15  
Impervious surface fraction  Ratio of impervious paver material to total area.  pave_impervious_surf_fraction  Double  3  0  
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.  pave_permeability  Double  Integer  3  100  
Pavement clogging factor  Number of pavement layer void volumes of runoff treated it takes to completely clog the pavement.  pave_clogging_factor  Double  3  0  
Soil class  The class of soil can be selected from a dropdown list.  soil_class  Text  20  
Soil thickness  Thickness of layer.  soil_thickness  Double  Pipe size  3  500  
Soil porosity  Porosity of the soil. This field is automatically populated when the soil Class is selected.  soil_porosity  Double  3  0.5  
Field capacity  Soil field capacity. This field is automatically populated when the soil Class is selected.  soil_field_capacity  Double  3  0.2  
Wilting point  Soil wilting point. This field is automatically populated when the soil Class is selected.  soil_wilting_point  Double  3  0.1  
Conductivity  Soil’s saturated hydraulic conductivity. This field is automatically populated when the soil Class is selected.  soil_conductivity  Double  Integer  3  12.7  
Conductivity slope  Slope of the curve of log (conductivity) versus soil moisture content.  soil_conductivity_slope  Double  3  10  
Suction head  Soil capillary suction. This field is automatically populated when the soil Class is selected.  soil_suction_head  Double  Pipe size  3  88.9  
Barrel height  Height of a rain barrel.  storage_barrel_height  Double  Pipe size  3  0  
Storage thickness  Thickness of the storage layer.  storage_thickness  Double  Pipe size  3  150  
Storage void ratio  The storage void ratio.  storage_void_ratio  Double  3  0.75  
Seepage rate  The filtration rate of the layer when first constructed.  storage_seepage_rate  Double  Integer  3  10  
Storage clogging factor  Number of storage layer void volumes of runoff treated it takes to completely clog the layer.  storage_clogging_factor  Double  3  0  
Flow coefficient  Coefficient C that determines the rate of flow through the underdrain as a function of height of stored water above the drain bottom.  underdrain_flow_coefficient  Double  3  0  
Flow exponent  Exponent n that determines the rate of flow through the underdrain as a function of height of stored water above the drain outlet.  underdrain_flow_exponent  Double  3  0.5  
Offset height  Height of underdrain piping or outlet above the bottom of the storage layer or rain barrel.  underdrain_offset_height  Double  Pipe size  3  150  
Delay  The number of dry weather hours that must elapse before the drain line in a rain barrel is opened.  underdrain_delay  Double  Hours  3  6  
Flow capacity  The flow capacity of the storage layer or rain barrel.  underdrain_flow_capacity  Double  4  6  
Mat thickness  The thickness of the drainage mat layer.  drainagemat_thickness  Double  Pipe size  3  75  
Mat void fraction  The void fraction of the drainage mat.  drainagemat_void_fraction  Double  3  0.5  
Mat roughness (Manning’s n)  Roughness of the drainage mat. 
Table 3. Only the 1st Columns from the Help File InfoWorks ICM SuDS Table
Field Name  Help Text 
Control ID  The name that identifies this control object. 
Control type  The type of SUDS control can be selected from the dropdown list. 
Berm height  Storage height. 
Storage depth  Storage depth. 
Vegetation volume fraction  Fraction of the area above the surface that is filled with vegetation. 
Surface roughness (Manning’s n)  Manning’s n for overland flow. This surface roughness cannot be 0 for permeable pavements, green roofs or vegetative swales. 
Surface slope  The gradient of the surface slope. 
Swale side slope  The gradient of the slope of side walls. 
Pavement thickness  The thickness of the pavement layer. 
Pavement void ratio  The void ratio of the pavement layer. 
Impervious surface fraction  Ratio of impervious paver material to total area. 
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. 
Pavement clogging factor  Number of pavement layer void volumes of runoff treated it takes to completely clog the pavement. 
Soil class  The class of soil can be selected from a dropdown list. 
Soil thickness  Thickness of layer. 
Soil porosity  Porosity of the soil. This field is automatically populated when the soil Class is selected. 
Field capacity  Soil field capacity. This field is automatically populated when the soil Class is selected. 
Wilting point  Soil wilting point. This field is automatically populated when the soil Class is selected. 
Conductivity  Soil’s saturated hydraulic conductivity. This field is automatically populated when the soil Class is selected. 
Conductivity slope  Slope of the curve of log (conductivity) versus soil moisture content. 
Suction head  Soil capillary suction. This field is automatically populated when the soil Class is selected. 
Barrel height  Height of a rain barrel. 
Storage thickness  Thickness of the storage layer. 
Storage void ratio  The storage void ratio. 
Seepage rate  The filtration rate of the layer when first constructed. 
Storage clogging factor  Number of storage layer void volumes of runoff treated it takes to completely clog the layer. 
Flow coefficient  Coefficient C that determines the rate of flow through the underdrain as a function of height of stored water above the drain bottom. 
Flow exponent  Exponent n that determines the rate of flow through the underdrain as a function of height of stored water above the drain outlet. 
Offset height  Height of underdrain piping or outlet above the bottom of the storage layer or rain barrel. 
Delay  The number of dry weather hours that must elapse before the drain line in a rain barrel is opened. 
Flow capacity  The flow capacity of the storage layer or rain barrel. 
Mat thickness  The thickness of the drainage mat layer. 
Mat void fraction  The void fraction of the drainage mat. 
Mat roughness (Manning’s n)  Roughness of the drainage mat. 
InfoWorks ICM can export networks to SWMM5 data format.
To export to SWMM5 file:
Alternatively, with a network open select Export  To SWMM5 files… from the Network menu. (When using this method, the latest version of the current scenario will be exported.)
This topic contains the following sections detailing export of InfoWorks ICM data to SWMM5 data format:
Exporter Limitations
The exporter currently supports asset data and export to the DWF section of the SWMM5 data file only.
The table below lists the SWMM5 sections that are not exported and the reason that the section is not exported:
SWMM5 section  Exporter Limitation 
Raingages
Evaporation Temperature Inflows Patterns Timeseries 
Event Data – the exporter currently supports asset data only (with the exception of DWF and RTK Hydrograph data). 
Pollutants
Landuses Coverages Buildup Washoff Erosion Sediment Treatment Loadings 
SWMM quality modelling is not directly equivalent to quality modelling in InfoWorks ICM 
Report
Files Dividers 
No InfoWorks ICM equivalent 
Snowmelt
Snowpack 
Not currently supported 
Groundwater
Aquifers 
SWMM Groundwater modelling is not directly equivalent to groundwater modelling in InfoWorks ICM 
General
The network description on the Description Page of the network Property Sheet is exported to the TITLE section of the SWMM5 file.
Options
The SWMM5 OPTIONS section defines system properties and analysis options. The majority of options are not set on export and will be set to the SWMM5 default values.
The following options are set on export:
Flow Units
InfoWorks ICM networks are exported to SWMM5 data files with units based on the flow units that the user currently has set in InfoWorks ICM.
InfoWorks ICM Flow Unit  SWMM5 Flow Unit 
m3/s  CMS 
ft3/s  CFS 
l/s  LPS 
MGD  MGD 
US Gal/min  GPM 
Infiltration
SWMM supports one runoff volume model per network. If more than one of the SWMM5 infiltration models is used in the InfoWorks ICMnetwork, the exporter sets the Infiltration field to MIXED. This will generate an error message in SWMM5. Infiltration parameters will not be exported to the SWMM5 INFILTRATION section.
Runoff volume models in SWMM can be: Horton (exported as "HortonSWMM"), GreenAmpt or Curve Number. Any other InfoWorks ICM runoff volume models are exported as "HortonSWMM". If more than one runoff volume model is used in the InfoWorks ICM network, Infiltration parameters will be exported as zero to the SWMM5 INFILTRATION section.
Allow Ponding
This field is set to NO if the flood type for manhole nodes is set to "LOST", or YES if the flood type is "STORED".
If there is a mixture of "STORED" and "LOST" flood types in the network, this field will be set to YES, and a warning message will be exported to the SWMM5 file.
Subcatchments
Subcatchment information is exported to the SUBCATCHMENTS and DWF sections of the SWMM5 file.
Runoff Surface information is exported to the SUBAREAS and INFILTRATION sections of the SWMM5 file.
RTK Hydrograph information is exported to the HYDROGRAPHS and RDII sections of the SWMM5 file.
Subcatchment data field mapping
Field mappings and conversions of InfoWorks ICM Subcatchment fields to SWMM5 SUBCATCHMENT fields:
SWMM5 Parameter  InfoWorks ICM Export 
Name  Subcatchment ID 
Raingage  Rainfall Profile 
Outlet  Node ID 
Area  Total Area 
%Imperv  %Imperv = 100 x (Sareaimp/ Sareas)
where: Sareaimp = sum of surface areas of type impervious Sareas = sum of surface areas (The exporter treats surfaces of type "unknown" as pervious for the purposes of calculating %Imperv) 
Width  Dimension 
Slope  Slope 
Clength  Zero
(There is no equivalent in InfoWorks ICM to this field) 
Runoff Surface  Runoff Surface information is exported to the SUBAREAS section of the SWMM5 file. 
DWF Data Field Mapping
Data is exported to the DWF section of the SWMM5 file for subcatchments with nonzero Additional Foul Flow or nonzero Population fields.
Note: Patterns are not exported for the dry weather flow profile names created. These must be created in SWMM.
Field mappings and conversions of InfoWorks ICM Subcatchment fields to SWMM5 DWF fields:
SWMM5 Parameter  InfoWorks ICM Export 
Node  Node ID 
Item  FLOW 
Value  For subcatchments with nonzero Additional Foul Flow:
For subcatchments with nonzero Population:

Pat 1  For subcatchments with nonzero Additional Foul Flow:
For subcatchments with nonzero Population:

Pat 2  For subcatchments with nonzero Additional Foul Flow:
For subcatchments with nonzero Population:

Pat 3  For subcatchments with nonzero Additional Foul Flow:
For subcatchments with nonzero Population:

Pat 4  Not used. 
Subarea data field mapping
Field mappings and conversions of InfoWorks ICM Runoff Surfaces fields to SWMM5 SUBAREA fields:
SWMM5 Parameter  InfoWorks ICM Export 
Subcatch  Subcatchment ID 
Imperv_N  Runoff Routing Value for Impervious surfaces using SWMM Routing Model.
If more than one surface is Impervious, the value exported is an average weighted by surface area. If Routing Model is not SWMM, Imperv_N exported as zero. 
Perv_N  Runoff Routing Value for Pervious surfaces using SWMM Routing Model.
If more than one surface is Pervious, the value exported is an average weighted by surface area. If Routing Model is not SWMM, PervN exported as zero. 
Imperv_S  Initial Loss Value for Impervious surfaces.
Slope related values are converted to absolute values. If more than one surface is Impervious, the value exported is an average weighted by surface area. 
Perv_S  Initial Loss Value for Pervious surfaces.
Slope related values are converted to absolute values. If more than one surface is Pervious, the value exported is an average weighted by surface area. 
PctZero  Percent of impervious area with no depression storage:
PctZero = Sum of areas of Impervious surfaces with no initial loss/Sum of areas of impervious surfaces 
RouteTo  OUTLET 
Infiltration
Infiltration parameters on the Runoff Surfaces tab of the subcatchments grid are exported to the INFILTRATION section of the SWMM5 file.
The Subcatchment ID is exported to the SWMM5 Subcatch field. The export of infiltration parameters depends on the infiltration model being used. Infiltration parameters are exported as zero for any subcatchments that do not use the infiltration model defined in the OPTIONS section of the SWMM5 file.
Horton Infiltration
Field mappings and conversion of InfoWorks ICM Runoff Surface fields to SWMM5 INFILTRATION fields when using Horton Runoff Volume Type:
SWMM5 Parameter  InfoWorks ICM Export 
MaxRate  Horton Initial 
MinRate  Horton Limiting 
DecayRate  Horton Decay 
DryTime  Horton Drying Time 
MaxInfil  Horton Max Infiltration Volume 
GreenAmpt Infiltration
Field mappings and conversions of InfoWorks ICM Runoff Surface fields to SWMM5 INFILTRATION fields when using GreenAmpt Runoff Volume Type:
SWMM5 Parameter  InfoWorks ICM Export 
Suction  Green Ampt Suction 
Conduct  Green Ampt Conductivity 
InitDef  Green Ampt Deficit 
Curve Number Infiltration
Field mappings and conversions of InfoWorks ICM Runoff Surface fields to SWMM5 INFILTRATION fields when using SCS / CN Runoff Volume Type:
SWMM5 Parameter  InfoWorks ICM Export 
CurveNo  Runoff Curve Number
When using SCS Runoff Volume Type, Storage depth is converted to CN using: S = (1000/CN – 10) * 0.0254 where: S in meters 
Conduct  Zero 
Regen  Zero 
RTK Hydrographs
RTK Hydrograph parameters on the RTK Hydrograph tab and applicable Monthly RTK Hydrograph tab of the subcatchments grid are exported to the HYDROGRAPHS section of the SWMM5 file.
For model networks which were created using an earlier version of InfoWorks ICM than version 8.0, and which have not been subsequently updated, then for cases where the RTK Hydrograph is associated with different rainfall profiles, a hydrograph will be exported for each rainfall profile that it is used with. This does not apply from version 8.0 onwards, as the same rainfall profile must be specified for all subcatchments that use the same RTK hydrograph.
SWMM5 Parameter  InfoWorks ICM Export 
Name  RTK Hydrograph ID appended by rainfall profile number 
Raingage  Rainfall Profile to which RTK Hydrograph is applied 
Month  ALL (for RTK Hydrograph)
Appropriate Month(s) (for Monthly RTK Hydrograph) 
R1, R2, R3  R1, R2, R3 
T1, T2, T3  T1, T2, T3 
K1, K2, K3  K1, K2, K3 
Dmax1, Dmax2, Dmax3  Max depth – Short term, Max depth – Medium term, Max depth – Long term 
Drec1, Drec2, Drec3  Recovery rate Short term, Recovery rate Medium term, Recovery rate Long term 
D01, D02, D03  Starting depth – Short term, Starting depth – Medium term, Starting depth – Long term 
RDII section
RTK Hydrograph information is also exported to the RDII section of the SWMM5 file.
For model networks which were created using an earlier version of InfoWorks ICM than verison 8.0, and which have not been subsequently updated, then if there are two or more subcatchments draining to the same node that use RTK hydrographs, only one RTK hydrograph will be given as the property of the node exported to SWMM5. This does not apply from version 8.0 onwards, as only one RTK hydrograph can be specified for any subcatchment that drains to the same node.
SWMM5 Parameter  InfoWorks ICM Export 
Node  Node ID of node to which subcatchment drains 
UHGroup  RTK Hydrograph associated with subcatchment draining to node 
SewerArea  Contributing Area of subcatchment draining to node 
Nodes
Node data is exported to the JUNCTIONS, OUTFALLS or STORAGE section of the SWMM5 file, depending on the type of node.
Field mappings and conversions of InfoWorks ICM node fields to SWMM5 node fields:
SWMM5 Parameter  InfoWorks ICM Export 
Name  Node ID 
InvertEl  Chamber Floor Level 
MaxDepth  MaxDepth = Ground Level– Chamber Floor Level 
InitDepth  Exported as Zero.
(There is no equivalent in InfoWorks ICM, as InfoWorks ICM automatically initialises levels.) 
Manhole / Break Nodes
Manhole and break node data is exported to the Junctions section of the SWMM5 file.
SWMM5 Parameter  InfoWorks ICM Export 
SWMM5 Parameter  InfoWorks ICM Export 
SurDepth  Lost/Stored Flood Type = Zero
Sealed Manholes = 999 m (3277.6 ft) 
Ponded Area  Floodable Area 
Outfalls
All outfalls are exported as FREE outfalls with NO flap gate.
Outfall node data is exported to the Outfalls section of the SWMM5 file.
Storage Nodes
Storage node data is exported to the Storage section of the SWMM5 file.
Storage Nodes are exported as Type TABULAR. The Level/Plan Area Grid defining the shape of the storage node on the Storage Parameters Page of the Node Property Sheet is exported to the Curvessection of the SWMM5 file. The Table name is exported as the Storage Node ID.
Links
Link data is exported to the CONDUITS section of the SWMM5 file.
Common Link data fields:
SWMM5 Parameter  InfoWorks ICM Export 
Name  Link ID 
Node1  US Node ID 
Node2  DS Node ID 
Conduits
Conduit data is exported to the CONDUITS section of the SWMM5 file.
The crosssection data for conduits is defined in the XSECTION section of the SWMM5 file.
The upstream and downstream headloss coefficients of a conduit are exported to the LOSSESsection of the SWMM5 file.
SWMM5 Parameter  InfoWorks ICM Export  
Length  Length  
Nvalue  Top Roughness
(A warning message will be generated in the exported SWMM5 text file if the Top Roughness differs from the Bottom Roughness) ColebrookWhite values are converted to N by:
where: ks in metres HazenWilliams values are converted to N by: Where: conduit_height is in ft (If conduit gradient is zero, the above equation will fail. For conduits with zero gradient, a gradient value of 0.0001 will be used for conversion purposes.) 

Zup  US Invert Level – Chamber Floor Level (US Node)  
Zdown  DS Invert Level – Chamber Floor Level (DS Node)  
InitFlow  Zero 
Flap Valves
Flap valves are exported to the CONDUITS section of the SWMM5 file. Flap Valves are exported with a nominal length of 1m (3.28ft). Backflow is prevented by including an entry in the LOSSESsection.
The crosssection data for flap valves is defined in the XSECTION section of the SWMM5 file.
Pumps
Pump On and Off levels are exported as CONTROLS.
Field mappings and conversions of InfoWorks ICM Pump data to SWMM5 PUMP fields:
SWMM5 Parameter  InfoWorks ICM Export 
CurveName  Pump ID
(The Head Discharge table is exported to the CURVES section of the SWMM5 file.) 
InitStatus  This is not exported as it is event data.
SWMM5 default value = ON 
Orifices / Sluice Gates
All orifices and sluice gates are exported as an orifice of Type SIDE with NO flap gate.
Orifice and Sluice Gate data is exported to the ORIFICE section of the SWMM5 file.
The geometry of the orifice opening is defined in the XSECTION section of the SWMM5 file.
Field mappings and conversions of InfoWorks ICM Orifice and Sluice Gate data to SWMM5 ORIFICE fields:
SWMM5 Parameter  InfoWorks ICM Export 
Type  SIDE 
Height  Height = Invert Level– Chamber Floor Level (US node) 
Cd  
Flap Gate  NO 
Weirs
The geometry of the weir opening is defined in the XSECTION section of the SWMM5 file.
Field mappings and conversions of InfoWorks ICM Weir data to SWMM5 WEIRS fields:
SWMM5 Parameter  InfoWorks ICM Export  
Type 


Height  Crest – Chamber Floor Level (US node)  
Cd  Discharge Coefficient  
Flap Gate  NO  
EC  Zero for all types 
Outlets
User defined links, culvert inlet, culvert outlet, flume, screen and siphon links are exported to the OUTLETS section of the SWMM5 file.
Field mappings and conversions of InfoWorks ICM link data to SWMM5 OUTLETS fields:
SWMM5 Parameter  InfoWorks ICM Export 
Height  Crest or Invert Level– Chamber Floor Level (US node) 
Discharge Curve  TABULAR 
Qtable  Link ID
Please Note The Head Discharge table for User Defined Links is exported to the Curves section of the SWMM5 file. HQ curves must be defined by the user for all other Link types exported as outlets. 
Flap Gate  NO 
River Channel Sections
River channel sections are exported to the CONDUITS section of the SWMM5 file.
The crosssection geometry of channel river sections is defined in the XSECTION and TRANSECTS sections of the SWMM5 file.
Cross Sections
Cross Section data for conduits, river channels, orifices, sluices, flap valves and weirs are exported to the XSECTION section of the SWMM5 file.
For regular shaped sections:
SWMM5 Parameter  InfoWorks ICM Export 
Link  Link ID 
Shape  See Shape Table below. 
Geom1  Height
Diameter for Flap Valves 
Geom2  Width 
Geom3  Left Side Slope for Trapezoidal sections
0.249328 for Trapezoidal Weirs Zero for all other shapes 
Geom4  Right Side Slope for Trapezoidal sections
Zero for all other shapes 
For river channel sections:
SWMM5 Parameter  InfoWorks ICM Export 
Link  Link ID 
Shape  IRREGULAR 
Transect  Link ID 
Cross Section Shape Types
InfoWorks ICMLink Type  SWMM5 Shape  
Conduit 
If there is no SWMM5 equivalent to the CS Shape ID, a Shape of "UNKNOWN" is exported. This will create an error message in SWMM5 when the file is opened. 

Flap Valve  CIRCULAR  
Orifice  CIRCULAR  
Sluice Gate  RECT_CLOSED  
Weir 

Transects
The crosssection geometry of river channel sections is exported to the TRANSECTS section of the SWMM5 file.
Field mappings and conversions of InfoWorks ICM river channel data to SWMM5 TRANSECTS fields:
SWMM5 Parameter  InfoWorks ICM Export 
Nleft  Rough.
The roughness value in the CrossSection grid up to the first panel marker 
Nright  Rough.
The roughness value in the CrossSection grid after the last panel marker 
Nchannel  Rough.
The roughness value in the CrossSection grid between panel markers 
Name  Channel Link ID 
Nsta  Number of entries in River Channel CrossSection grid 
Xleft  The X Coord. value in the CrossSection grid of the first section that has a new panel set.
If there are no panel markers, this is the first X value in the grid. 
Xright  X Coord.
The X Coord. value in the CrossSection grid of the last section that has a new panel set. If there are no panel markers, this is the last X value in the grid. 
Wfactor  Zero 
Eoffset  US Invert Level 
Station(n)  X Coord.
The X Coord. value in the CrossSection grid for grid entry (n), where (n) = 1 to Nsta. 
Elevation(n)  Depth
The Depth value in the CrossSection grid for grid entry (n), where (n) = 1 to Nsta. 
Minor Losses
The upstream and downstream headloss coefficients of a conduit are exported to the LOSSES section of the SWMM5 file. Entries are also included for flap valves to prevent backflow in the conduit.
SWMM5 Parameter  InfoWorks ICM Export 
Conduit  Conduit ID 
EntryLoss  US Headloss Coefficient
For Headloss Type of NORMAL or HIGH, the headloss coefficient is multiplied by 0.15. 
ExitLoss  DS Headloss Coefficient
For Headloss Type of NORMAL or HIGH, the headloss coefficient is multiplied by 0.015 
AvgLoss  Zero 
FlapGate  Conduit = NO
Flap Valve = YES 
Controls
Pump On and Off levels are exported as controls.
Click on the image below to display the example.
Curves
Level/Plan Area grids for Storage Nodes are exported to the CURVES section of the SWMM5 file.
Head Discharge tables for Pumps and User Control Links are exported to the CURVES section of the SWMM5 file.
SWMM5 Parameter  InfoWorks ICM Export  
Name  Link ID  
Type 


X(n) 


Y(n) 

Coordinates
X and Y coordinates of nodes are exported to the COORDINATES section of the SWMM5 file.
X and Y coordinates of bends in links are exported to the VERTICES section of the SWMM5 file.
X and Y coordinates of vertices in polygons are exported to the POLYGONS section of the SWMM5 file.
Storm Water Management Pond Example with Manhole Flooding, Overland Flow Routing, Pond Evaporation, Pond Losses and Conduit Design.
.
Introduction
Visual Hydro/Visual SWMM can comprehensively model storm water management systems that include mixtures of open channel and closed conduits. It can also model closed sanitary or wastewater systems. The hydraulic calculations in SWMM support looped networks, storage nodes such as ponds, backwater and multiple outfalls. This tutorial contains all of these components and introduces some advanced options for modeling pond losses and handling flooding in a stormwater network.
Skills to be learned
Loading and Manipulating Background Files
Digitizing Network Objects on Scaled Backgrounds
Renaming Network Objects
Layer Control and Object Association
Entering Data in Dialogs and Using Copy and Paste
Importing XY Coordinates
Exporting Data to XPX File
Trouble Shooting Error Messages and Running the Model
Interpreting Flooding Using Review Results, Long Section and the Output File
Attaching Images and Notes to Nodes
Adding and Removing the Vertices on a PolyLink
Modeling Pond Losses with Equations
Screening the Model with Spatial Reports and Graphical Encoding
Designing Single or Entire Set of Conduits in Hydraulics Layer
Duplicating Global Databases for Design Rainfall
Files Needed
GIRA.PIC
YUCH.BMP
Loading the Background
The load background command is located at Special=>Get Background in the Visual SWMM interface.
Use the File GIRA.PIC, a converted HPGL file and load it to the real world coordinates shown below. At first you will not see any background picture, but fit the graphics to the screen with the command View=>Fit Window or use the Fit to Window Icon. The picture will be in the center of the screen.
The following tool strip is used to manipulate backgrounds. Holding the mouse over the icon will display a bubble of the icon’s purpose and a detailed description of the command is displayed in the lower left hand corner of the screen.
Digitizing Network Objects on Scaled Backgrounds
Digitize using the XP Object Toolstrip Icons the links and nodes in the network as shown below. New objects will be labeled successively from 1. We will rename the objects at a later time. The orientation of the links is important and the arrow on a link marks US to DS. Do not create the objects loss, exfiltration or swale, as they will be added later. Try to place objects close to the locations shown below. Later we will import a coordinate file to fix the locations.
Renaming Network Objects
Objects can be renamed in three ways. Use the names as shown on the previous page.
Method 1
Highlight the node or link and then use the command Edit=>Attributes. This will display a different dialog for a node or a link that displays a field for entering the object name. Then doubleclick with the mouse to overwrite the current cell contents and key in the new name. The field will accept up to 10 characters alpha numeric.
Method 2
Right mouseclick on the object, which will bring up a popup dialog allowing attributes to be selected. Node Link
Method 3
Select the object then doubleclick on the object’s label and a user entry field will appear where the object’s name can be edited. Follow the entry with an enter key and the new name will appear.
Try using all three methods for this tutorial. When they are all updated, save your work.
Layer Control
An object, a link or node has a common name in all layers of Visual SWMM. Using the + and – icons on the Toolstrip the object can be activated for solving in the current layer.
Switch to the RUNOFF layer by selecting Rnf from the Toolstrip and add nodes MH2, MH4, MH6, MH8, MH3, MH1, and Detention to the RUNOFF layer by selecting these objects and then selecting the + icon. Objects can be added or removed to a selection set by holding down the shift key and selecting with a left mouse click.
Interface Files
Flows and pollutant concentrations can be stored on binary interface files which are created from a model solve. Each of the layers can read certain types of interface files with the most common set up using rainfall interface files into Runoff, Runoff saving the flows for all active nodes and Hydraulics reading the existing Runoff layer interface file. Interface files are designated using the command Tools=>Interface Files while in each appropriate layer.
Interface file names and object selections along with inappropriate dates are the most common user errors. If flows are generated in Runoff but they do not appear in the Extran layer then check dates, file names and make sure that no conduits are active in more than one layer.
Entering Data in Dialogs
The most straightforward method of data entry in VISUAL SWMM is to enter data to the objects through dialogs. To access these dialogs doubleclick with the left mouse button on the object. An alternative and much more cumbersome method to access the dialogs is to select the object and then use the command Edit=>Data. These first level dialogs contain the most common data for links and nodes. Other data is entered in dialogs spawned by selecting buttons on these dialogs and some data such as rainfall is entered in a global database. Details of the global database will be dealt with later. The first dialogs of the node and link are shown below. The node dialog is layer dependent and shows different data depending on the active layer. Note that the object name is displayed in the dialog title bar.
To enter data in the dialog click with the mouse on the field and begin typing. To navigate to another field click or choose the tab key. Selecting OK causes an embedded expert system to check the data. If the data is not valid or unreasonable an error message or warning will be displayed. Selecting OK also closes the dialog and commits the data to the database. Cancel will ignore any changes that have been made and will not invoke the data checking.
The data to be entered in this project is outlined in the Tables are on the next page.
Subcatchment Physical Data (Runoff Nodes)
Node Name  Subcatchment
Number 
Area, ha
(R_WAREA) 
%Impervious (R_WIMP)  Width, m
(R_WIDTH) 
Slope, m/m
(R_WSLOPE) 
MH 1  1  1.08  16  105  0.015 
MH 2  1  0.473  16  65  0.015 
MH 2  2  0.283  20  50  0.02 
MH 3  1  0.435  24  120  0.015 
MH 4  1  0.23  31  45  0.012 
MH 6  1  0.235  16  55  0.005 
MH 8  1  0.65  20  95  0.016 
detention  1  2  30  100  0.005 
Manhole Data (Hydraulics Nodes)
Node Name  Spill Crest (GRELEV)  Invert (Z) 
MH 1  410.5  407 
MH 2  413  410 
MH 3  409  406.2 
MH 4  411  408 
MH 6  409  406 
MH 8  406  403.5 
detention  400  397 
outfall  396  390 
Conduit Data
Conduit Name  Shape
(NKLASS) 
Length, m
(LEN) 
Roughness
(ROUGH) 
Conduit US
Invert, m (ZP1) 
Conduit DS
Invert, m (ZP2) 
Diameter or Depth, m
(DEEP) 
Pipe A1  Circular (1)  112.00  0.014  407.00  406.20  0.300 
Pipe A2  Circular (1)  112.00  0.014  410.00  408.00  0.300 
Pipe A3  Circular (1)  70.00  0.014  406.20  406.00  0.300 
Pipe A4  Circular (1)  76.00  0.014  408.00  406.00  0.300 
Pipe A6  Circular (1)  134.00  0.014  406.00  403.50  0.400 
Pipe A8  Circular (1)  57.00  0.014  403.50  399.00  0.400 
Control  orifice  –  –  –  –  0.060 
Note: Pipe Slopes are not required data in the Extran layer. Any Value in that field will be ignored, however the expert system will notify with warnings if the data for slope does not match the inverts and length. Simply select the Solve routine in the conduit profile dialog to have the software calculate the slope for you.
This would be a good point to save your work.
Orifice Data
The orifice is circulat side outlet orifice at an elevation of 399 and an area of 0.1 m2.
Infiltration Data in the Global Database
The Global Database for a new project is empty since this information is internal to the XP file. The information can be entered into the Global Database by Selecting the command Tools=>Global Data. Select the Database Type as Infiltration on the left side of the dialog. Then add the record soil and select enter the data as shown below.
Rainfall Data in the Global Database
Select the Database Type as
Rainfall and add the record SCS Type II as shown below: Copy Icon
By using cumulative depth as the rainfall type then the hyetograph is easily scaled for depth and duration by using the multiplier and time controls. These screen shots show a 35mm depth over 6 hours, our hypothetical 2yr return period. Not shown is the final value of 1.000 that would be entered by using the down arrow with the cursor in the sixth row.
With this record entered it can be duplicated and new multipliers entered that will represent the depth for a greater return period.
After the global databases have been entered go to the Subcatchment 1 of MH 1 and select the SCS Type II for the rainfall and Soil for the Infiltration records to be attached to this subcatchment. Then select the SCS Type II labeled button with the mouse and choose the Copy icon in the upper right hand corner of the dialog.
With this record now copied the rainfall can be attached to all nodes by returning to the network window and selecting the command Edit=>Paste Data. This pastes the “reference” to the global database record to all nodes for subcatchment 1. Since Node MH 2 has two subcatchments the fields will have to be updated by selecting. Of course if many nodes had 2nd subcatchments then we could copy and paste that field.
This process needs to be repeated for the infiltration record “soil” that must be attached for all node subcatchments.
Additional Data for Outfalls and Storage Data
The “outfall” node should have the outfall button checked and free outfall selected (Type 1) using as the control the minimum of Yc or Yn.
The node “detention” has storage properties as shown below using Stepwise Linear, and a Node Surcharge Elevation of 400 m. The depth field is the depth to the node invert and the are is in units of hectares.
Job Control (Simulation Limits and Criteria)
Separate Job Control data is required for Runoff Layer and the Hydraulics Layer. This data sets the simulation start and simulation end as well as time step.
Buttons without check boxes are mandatory, so in reference to the Runoff layer the Evaporation, Time Control, and Print Control data is required and is shown below.
For the Hydraulics Layer, simply select the same time period and choose an appropriate time step. In this simulation we will use 15 seconds. All other data is optional and should be used with discretion.
The last item to select to make our model run is the Mode Properties. This dialog directs the program to which layers (modes) should be solved. We will choose as solve mode Runoff and Hydraulics by selecting the command Tools=>Mode Properties.
Importing XY Coordinates for the Nodes using XPX
Although the nodes were digitized on the screen and coordinates were assigned they are only as accurate as the screen placement. However, the node coordinates are able to be stored with double precision.
Select the command Special=>Import Data:XPX and choose the file coord1.xpx. The contents of this file is shown below. Select the Import Button to perform the command, whereas the OK button stores the changes made in this dialog.
COORD1.XPX
NODE 134 "MH 2" 208107 611922
NODE 134 "MH 4" 208165 612018
NODE 134 "MH 6" 208225 611971
NODE 134 "MH 8" 208155 611857
NODE 133 "detention" 208161 611797
NODE 134 "MH 1" 208268 611828
NODE 134 "MH 3" 208287 611938
NODE 134 "outfall" 208220 611794
NODE 134 "exfiltration" 208160 611767
NODE 134 "emergency" 208082 611868
This node command creates or updates a node nominated in quotes to the x and y coordinates specified. We are using it to precisely place the nodes at the “known” GPS coordinates.
Exporting the Data to an XPX File
Similar to importing XPX files the data entered can be exported to a text file. To export all the data or a selection of data choose the command Special=>Export Data to see the following dialog:
The Select Button allows the user to pick a list of data to export.
The XPX file generated can include data and results. A partial list is shown below including some results.
NODE 134 "MH 2" 208107 611921
NODE 134 "MH 4" 208165 612018
NODE 134 "MH 6" 208225 611971
NODE 134 "MH 8" 208155 611857
NODE 133 "detention" 208161 611797
NODE 134 "MH 1" 208268 611828
NODE 134 "MH 3" 208287 611938
NODE 134 "outfall" 208220 611794
NODE 134 "exfiltration" 208160 611767
NODE 134 "emergency" 208082 611868
LINK 136 "Pipe A2" "MH 2" "MH 4"
LINK 136 "Pipe A4" "MH 4" "MH 6"
LINK 136 "Pipe A6" "MH 6" "MH 8"
LINK 136 "Pipe A8" "MH 8" "detention"
LINK 136 "Pipe A1" "MH 1" "MH 3"
LINK 136 "Pipe A3" "MH 3" "MH 6"
LINK 138 "control" "detention" "outfall"
LINK 138 "loss" "detention" "exfiltration"
LINK 136 "swale" "MH 3" "detention"
LINK 136 "spillway" "detention" "emergency"
DATA R_NODEFLOW "MH 2" 0 1 0
DATA R_RESSAVENODE "MH 2" 0 1 0
DATA R_RFCMNT "MH 2" 0 5 1 1 0 0 0
DATA R_WAREA "MH 2" 0 5 .473 .283 "" "" ""
DATA R_WIMP "MH 2" 0 5 16. 20. "" "" ""
DATA R_WIDTH "MH 2" 0 5 65. 50. "" "" ""
DATA R_WSLOPE "MH 2" 0 5 0.015 0.02 "" "" ""
DATA R_WQTAG "MH 2" 0 1 1
DATA R_WQTAG "MH 2" 1 1 1
DATA R_SMTAG "MH 2" 0 1 0
DATA R_SMTAG "MH 2" 1 1 0
DATA R_GWTAG "MH 2" 0 1 0
DATA R_GWTAG "MH 2" 1 1 0
DATA R_GWFLAG "MH 2" 0 1 0
DATA R_GWFLAG "MH 2" 1 1 0
DATA R_RAINSEL "MH 2" 0 1 "SCS Type II"
DATA R_RAINSEL "MH 2" 1 1 "SCS Type II"
DATA R_INFILSEL "MH 2" 0 1 "soil"
DATA R_INFILSEL "MH 2" 1 1 "soil"
DATA R_FSCS "MH 2" 0 1 0
DATA R_FSCS "MH 2" 1 1 0
DATA R_ERLEN "MH 2" 0 1 0.0
DATA R_ERLEN "MH 2" 1 1 0.0
DATA R_ERTAG "MH 2" 0 1 0
DATA R_ERTAG "MH 2" 1 1 0
DATA T_NTYPE "MH 2" 0 1 19
DATA T_NSAVREV "MH 2" 0 1 1
DATA T_FOUTS "MH 2" 0 1 1
DATA T_FSEWIN "MH 2" 0 1 0
DATA T_NYN "MH 2" 0 1 0
DATA T_NPE "MH 2" 0 1 0
DATA T_QCON "MH 2" 0 1 .01
DATA T_FUDEF "MH 2" 0 1 1
DATA T_FCHCGO "MH 2" 0 1 0
DATA T_FCON "MH 2" 0 1 1
DATA GRELEV "MH 2" 0 1 413.
DATA Z "MH 2" 0 1 410.
DATA QINST "MH 2" 0 1 0.
DATA Y0 "MH 2" 0 1 0.
DATA NODST "MH 2" 0 1 0
DATA FLGOUTF "MH 2" 0 1 0
DATA SFLOOD "MH 2" 0 1 0
DATA INQ "MH 2" 0 1 0
DATA JPRT "MH 2" 0 1 0
DATA JPLT "MH 2" 0 1 0
DATA JNRR "MH 2" 0 1 0
DATA ICAP "MH 2" 0 1 0
DATA GINFLOW "MH 2" 0 1 0
DATA R_RSRFRUN "MH 2" 0 1 21.0889537
DATA R_RRAINFL "MH 2" 0 1 35
DATA R_RINFILT "MH 2" 0 1 15.0984068
DATA R_RGRDFLO "MH 2" 0 1 0
DATA R_RTOTIIF "MH 2" 0 1 0
DATA R_RNSURCH "MH 2" 0 1 0
DATA R_RTLLOAD "MH 2" 0 2 0 .022521466
DATA R_RMNCONC "MH 2" 0 2 0 0
DATA R_RMXCONC "MH 2" 0 2 0 4.19094411
DATA R_RTBULDP "MH 2" 0 2 0 0
DATA R_RTWASHF "MH 2" 0 2 0 .637357500
DATA R_RPWASHF "MH 2" 0 2 0 0
DATA R_RMAXFLO "MH 2" 0 1 .140501867
DATA R_RRUNVOL "MH 2" 0 1 21.0889537
DATA R_RMXIFRT "MH 2" 0 1 5.59166453
DATA R_RMNINRT "MH 2" 0 1 1.58999786
DATA R_RTTLINF "MH 2" 0 1 0
DATA R_REVAPSF "MH 2" 0 1 .011750122
DATA R_REVAPGW "MH 2" 0 1 0
DATA R_RWATCNT "MH 2" 0 1 0
DATA R_RGRDLDA "MH 2" 0 1 0
DATA R_RMXGRDP "MH 2" 0 1 0
DATA R_RMXDBGS "MH 2" 0 1 0
DATA E_RNFLOOD "MH 2" 0 1 0
DATA E_RSRFDTH "MH 2" 0 1 .837030255
DATA E_RSRFELV "MH 2" 0 1 410.837030
DATA E_RSRFARE "MH 2" 0 1 1.22
DATA E_RVOLUME "MH 2" 0 1 1.13143736
DATA E_REGLELV "MH 2" 0 1 410.837030
DATA E_REGLREL "MH 2" 0 1 2.16296974
DATA E_RFREEBD "MH 2" 0 1 2.16296974
DATA E_RMNDITR "MH 2" 0 1 2.91956967
DATA E_RNSURCH "MH 2" 0 1 2.75
DATA E_RCONTER "MH 2" 0 1 .204390568
DATA E_RFLDLSS "MH 2" 0 1 1.4485E19
DATA E_RTNDITR "MH 2" 0 1 5699
DATA E_RNDINFL "MH 2" 0 1 156.229842
Trouble Shooting Error Messages and Running the Model
To solve a model the user must select the command Special=>Solve or select the Solve Icon (Space Shuttle) from the toolstrip. Before the Solve commences the entire database is checked for errors. These checks go beyond the checking performed when a dialog is closed with the OK button and ensure that no data is missing and that all of the dependencies are satisfied. For example all conduit inverts are checked against the invert elevations of the connecting nodes to ensure they are equal or higher.
Any errors are warnings are displayed in the user specified editor. This editor is selected in the SWMXP.INI file and by default is NOTEPAD.EXE. A shareware version of notepad plus is installed in the vhydro directory and allows multiple and large files to be edited.
The error and warning messages are comprehensive and tell the user which layer, which objects and an explanation of the problem. Since one error can cascade to create many problems work your way from the first to the last error by periodically rechecking the model by selecting solve. The errors can be redisplayed by selecting the command Special=>Show Errors or by minimizing the error screen and switching to that window.
Interpreting Flooding Using Review Results, Long Section and Output File
Each of these tools can be used to determine if flooding occurs, when and in the case of the output file the quantity. Selecting MH 3 and then the Tools=>Review Results command will show the HGL over time and that the HGL will reach the Ground Surface and remain at that level for some time.
Capabilities of interest in this function include: changing titles, zooming in the graph, marking data points, including labels, exporting graphics, and exporting data. Double clicking in the graph, right mouse clicking on the graph and selecting the options icon on the Toolstrip, accesses these commands.
The Tools=>Long Section command will animate the HGL within a selection of links. Select a continuous set of links (branching not allowed) and choose the Tools=>Long Section command or the Long Section Icon from the Toolstrip. Plotting elements other than conduits requires a length to be assigned for items such as orifices, weirs and pumps. Choose the Plot button in the multilink dialog to plot through these objects.
The Long Section command allows animation to play, stop, pause, move backward and forward step by step, rewind, speed up, slow down, zoom, pan, and various annotation. In this model we see the HGL at MH 3 is at the ground so flooding is occurring.
Using the command Special=>Browse File or clicking on the Notepad icon will allow the user to select the output file created from the Solve. The output file is the most comprehensive simulation report and it contains summaries and tables for the entire simulation. The Tables are numbered and a list of tables appears near the top of the output file. Table E20 lists flooding and surcharge results for each node. A sample is shown below:
Out of
System Stored in System
Junction Surcharged Flooded Flooded Maximum Ponding Allowed
Name Time (min) Time(min) Volume Volume Flood Pond Volume
The dialog box for the SCS peak discharge method is shown below.
· Unit System – English or SI unit.
· Solving Target – Peak discharge or time of concentration.
· Equations – Rational method or the SCS peak discharge method.
· SCS Rainfall Type – Select one of the SCS rainfall types (i.e., Types I, IA, II, or III)
· Curve Number – SCS’s dimensionless number that is used as a measure of runoff generation capability of a watershed (see Table 3.12). It is a function of soil, land cover and treatment.
· Rainfall Depth – 24hr cumulative design rainfall depth. This rainfall depth will be distributed across the 24hr duration according to the SCS rainfall type selected.
· Drainage Area – Area of the total watershed that drains to the location where the peaks flow is determined.
· Peak Discharge – Peak flow generated from the watershed.
Source: http://www.slideshare.net/damonweiss/workshoponstormwatermodelingapproaches
Conservation of energy involves a balance in total energy, expressed as head, between any upstream point of flow and a corresponding downstream point, including head losses caused by friction and the viscous dissipation of turbulence at bends and other appurtenances (i.e., form losses or minor losses). The energy equation states that the incoming energy plus the energy gain (addition) equals the outgoing energy plus the energy loss. The onedimensional steady flow form of the energy equation is
A typical graphical representation of the terms in Equation (1) is shown in the following figure.
Definition Sketch for (a) Open Channel Flow, and (b) Pressurized Pipe Flow
Gutters are the sections of roadway that run adjacent to the curb. Their purpose is to collect and convey surface runoff to drainage inlets and in turn to underground storm sewers. The corresponding spread of water onto the pavement, or top width of flow measured perpendicular to the edge of the roadway, is a primary concern from an analysis perspective. The lateral cross slope of a traffic lane facilitates drainage of incident rainfall to the gutter. Depending on the cross slope, conventional gutters may be grouped as uniform gutter (i.e., has uniform cross slope) or composite gutters (i.e., has multiple cross slopes).
Uniform Gutter Sections
Uniform gutters have a shallow, triangular cross section, with a curb forming the nearvertical leg of the triangle as shown in the following figure.
The governing equation for uniform gutters is given as
where Q = gutter flow rate (m3/s, ft3/s)
Kc = empirical constant (0.376 in SI, 0.56 in English)
n = Manning’s roughness coefficient
Sx = gutter cross slope (m/m, ft/ft)
SL = longitudinal slope of the road way (m/m, ft/ft)
T = spread (m, ft)
Spread T is related to depth at the curb, d, and flow area, A, by
Table 37: Manning’s n for Street and Pavement Gutters
Type of Gutter or Pavement  Manning’s n 
Concrete gutter, troweled finish  0.012 
Asphalt Pavement:  
Smooth texture  0.013 
Rough texture  0.016 
Concrete gutterasphalt pavement:  
Smooth  0.013 
Rough  0.015 
Concrete pavement:  
Float finish  0.014 
Broom finish  0.016 
Adapted from FHWA (2001)
Composite Gutter Sections
Evaluation of composite gutters requires additional consideration of flow in the depressed section. The depression serves to retain more water above inlet entrances and thus increases gutter flow capacity. The relationship between total discharge, Q, and depressed gutter flow, Qw, can be expressed as
where Qw and Qs represent portion of the gutter flows for the sections shown in the figure above (m3/s, ft3/s).
The relationship between Q and Qs is given as
where Eo = ratio of Qw to Q, or
(71)
where W = width of the depressed section (m, ft)
Sw = cross slope of the depressed section (m/m, ft/ft)
The slope terms and the width of depression are related through depth of the depression, a, as
where a is the gutter depression (m, ft) illustrated in the figure given above.
When the flow is Supercritical in an upstream section of a channel and is then forced to become subcritical in a downstream section, a rather abrupt change in depth usually occurs and considerable energy loss accompanies the process. This flow phenomenon, known as hydraulic jump, is described in the following figure.
If a hydraulic jump occurs in a rectangular channel, the depth y2 (known as conjugate depth) is expressed as a function of y1 and the Froude number (Fr) as follows:
where y2 = water depth in the section 2 ( m, ft)
y1 = water depth in the section 1 (m, ft)
Fr1 = Froude number at the section 1, defined as
where V1 = upstream velocity [V_{1} = Q/(y_{1}B)] (m/s, ft/s)
B = channel bottom width (m, ft)
Q = flow (m3/s, ft3/s)
The hydraulic jump dialog box is shown below.
· Flow Unit – Select the desired flow unit.
· Solving Target – Discharge, upstream depth or downstream depth.
· Upstream Depth – Supercritical flow depth at upstream of the jump.
· Downstream Depth – Subcritical flow depth at downstream of the jump.
· Discharge – Channel flow rate.
· Channel Bottom Width – Bed width of the channel.
· Area (Upstream/Downstream) – Flow area at upstream section and downstream section of the jump, respectively.
· Velocity (Upstream/Downstream) – Flow velocity at upstream section and downstream section of the jump, respectively.
· Froude Number (Upstream/Downstream) – Froude number at upstream section and downstream section of the jump, respectively.
· Critical Depth – Flow depth corresponding to the minimum specific energy for the flow rate.
· Head Loss in the Jump – Difference in specific energy at the upstream end and the downstream end of the jump.
Pump Characteristic Curve
Pump characteristic curves are usually presented graphically describing the relationship between pump head, hp, and the flow rate, Q using either an exponential equation or 3point quadratic form. The exponential pump characteristic curve is given as
where hc = the pump cutoff head associated with the zero flow condition (m, ft)
Kp = resistance coefficient
b = flow exponent
nR = pump speed ratio (the ratio of the actual pump speed to the rated pump
speed); for constant speed pump operation, nR is equal to 1.
Given three hp–Q points [h_{c}, (h_{p}_{,1}, Q_{1}), (h_{p}_{,2}, Q_{2})], the pump curve can be calculated as
If a single rated capacity (hrated, Qrated) is given, two more points can be added to the curve by assuming a shutoff head at zero flow equal to 133% of the design head and a maximum flow at zero head equal to twice the design flow. Then, the curve can be treated as a threepoint curve.
The 3point quadratic type of pump characteristic curve is
where ap, bp, cp are the coefficients of the quadratic curve.
The coefficients are calculated as
The combined inertia of pumps and motors driving them, including the connecting shafts and couplings, is required for transient analysis associated with the starting and stopping of pumps. The equations provided below are intended to be used as an initial guide to the inertia values that may be used as a reasonable first approximation, when more accurate data is not available. The total inertia for the pump/motor unit is the sum of both pump and motor inertias. The following inertia calculations are based on Thorley (2004).
Pump Inertias
From the linear regression analysis of 300 pump inertia data, two equations were developed for predicting the inertia I of pump impellers, including the entrained water and the shaft on which the impeller is mounted. The first equation represents the upper set of the data, and applies to single and doubleentry impellers, single and multistage, and horizontal and vertical, spindle machines.
where I = pump inertia (kg m2, lb ft2)
C1 = coefficients (0.03768, 0.6674)
P = power (kW, hp)
N = pump speed (rev/min)
The second equation is for lower set of the data and represents relatively small, singleentry, radial flow impellers of lightweight design. This is applied to relatively small pumps of lightweight design.
where C2 = coefficients (0.03407 in SI, 0.6244 in English)
Motor Inertias
Similar to pump inertia, linear regression of the motor inertia data yields the following equations.
where C3 = coefficients (0.0043 in SI, 0.0648 in English).
The dialog box for estimating time of concentration using the Kirpich method is shown below.
· Unit System – English or SI unit.
· Solving Target – Choose time of concentration.
· Equations – Select one of the eight empirical equations listed in the dialog box shown above.• Unit System – English or SI unit.
· Solving Target – Choose time of concentration.
· Equations – Select the desired time of concentration estimation equation among the available eight methods. The table given below described these equations in further detail.
· Length of Channel – Length of the longest overland flow path for the watershed in feet.
· Average Watershed Slope – Average slope for the longest flow channel.
· Length of Longest Channel – Length of the longest overland flow path for the watershed in miles.
· Elevation Difference Between Divide and Outlet – The difference in elevation ( in feet) between the upstream end of the flow path and the outlet of the watershed.
· Rainfall Intensity – Intensity of the design rainfall ( in/hr)
· Length of Flow Path – Length of the longest overland flow path for the watershed in feet. The product rainfall intensity and the length of flow path should be < 500.
· Slope of Flow Path –Average slope for the longest flow channel.
· Retardance Coefficient – Coefficient that accounts for friction effect of the channel material. Retardance factor ranges from 0.007 for smooth pavement to 0.012 for concrete and to 0.06 for dense turf. The product rainfall intensity and the length of flow path should be < 500.
· Runoff Coefficient – Refers to the runoff coefficient used in rational formula.
· Length of Overland Flow– Length of the longest overland flow path for the watershed.
· Surface Slope – Average slope of the watershed.
· Rainfall Intensity – Intensity of the design rainfall (in/hr).
· Length of Overland Flow – Length of the longest overland flow path for the watershed.
· Average Overland Slope – Average slope for the longest flow channel.
· Manning’s Roughness Coefficient – Resistance coefficient used in Manning equation.
· Length of Flow Path – Intensity of the design rainfall (in/hr).
· Average Watershed Slope – Average slope for the watershed.
· Curve Number (CN) – NRCS curve number used as an index of the watershed’s runoff generation potential.
· Length vs Velocity Chart – Specify average flow velocity for various channel lengths.
· Length of Flow – Length of the longest overland flow path for the watershed in feet.
· Average Watershed Slope – Average slope for the watershed..
· Coefficient Ky – Coefficient. KY ranges from 1.5 for light rain (intensity <0.8) to 1.1 for moderate rain (0.8 < intensity < 1.2), and to 0.7 for heavy rain (intensity >1.2)
· Overland Texture Factor – Overland texture factor. See Table 3.13.
· Time of Concentration – The time it takes for flow to travel from the hydraulically remotest point in the watershed to reach outlet of the watershed.
Discussions in the previous sections have focused on uniform flow hydraulics where flow depth y and flow velocity V remain constant along the channel. In this section, we consider gradually varied flow, which is a form of steady nonuniform flow characterized by gradual variations in flow depth and velocity and a free surface that always remains smooth (no abrupt changes).
The following equation represents the general energy equation for gradually varied flow (see the above figure), for a reach of in length
The friction slope Sf can be expressed using Manning’s equation
where K is defined as the conveyance factor
in SI units or
in English units.
Hence
where
is average of the upstream and the downstream conveyance factors.
Water surface profile for a channel can be generated by solving Equation (13). The channel would be divided into short reaches and computation for water surface elevation would be progressed from one end of the reach to the other end. The two most commonly used techniques for water surface profile computation are the direct step method and the standard step method. In the direct step method, depth at the other end of the reach is assumed and the length () of the reach would be evaluated based on known depth and velocity information at one end of the reach. In the contrary, the computation procedure of the standard step method involves determination of the depth based on predetermined reach length ().
Equation 13 can be used to derive the following two alternative forms of the graduallyvaried flow equations.
Equation 14 can be used to qualitatively evaluate gradually varied flow profiles on various channel slopes. The evaluation and subsequent classification of shapes is an important preliminary step to computing associated water surface profiles since it yields information about the location of hydraulic controls, the direction of computation (i.e., upstream for subcritical flow or downstream for supercritical flow), and whether depth is increasing or decreasing. Classification of profiles begins by establishing criteria upon which the water surface depends, namely slope of the channel and depth of flow relative to the critical and normal depths (i.e., yc and yn). The criteria are as follows:
These criteria can be used to define the water surface profiles shown in the following figure. For example, an M1 profile exists when y > yn > yc. Under these conditions, Fr < 1 since y> yc, and Sf < So since y > yn. Thus, the sign of the numerator and denominator in Equation 14 are both positive, and dy/dx must be positive. The implication is that depth will increase with x, typically referred to as a backwater curve. Flow will also approach the normal depth upstream. Alternatively, for an M2 profile, yn > y > yc, so that the sign of dy/dxmust be negative. In this case, depth decreases with x, which represents a drawdown curve. Similar analyses can be made for other profiles. Note that horizontal and adverse slopes are unique cases in that the normal depth does not exist for either case. In addition, certain theoretical aspects of some profiles do not correlate well with realistic, physical behavior. For example, complete development of an M3 profile is unlikely; upstream flow cannot be zero, and the downstream end of the profile will likely be overcome by a hydraulic jump.
Wave Speed
The wave speed, c, is influenced by the elasticity of the pipe wall. For a pipe system with some degree of axial restraint a good approximation for the wave propagation speed is obtained using
where Ef = elastic modulus of the fluid (for water, 2.19 GN/m2, 0.05 Glb/ft2)
ρ = density of the fluid (for water, 998 kg/m3, 1.94 slug/ft3)
Ec = elastic modulus of the conduit (GN/m2, Glb/ft2)
D = pipe diameter (mm, inch)
t = pipe thickness (mm, inch)
KR = coefficient of restraint for longitudinal pipe movement.
The constant KR takes into account the type of support provided for the pipeline. Typically, three cases are recognized with KR defined for each as follows (m is the Poisson’s ratio for the pipe material):
Case a: The pipeline is anchored at the upstream end only.
KR = 1 – m / 2
Case b: The pipeline is anchored against longitudinal movement.
KR = 1 – m2
Case c: The pipeline has expansion joints throughout.
KR = 1
The following table provides physical properties of common pipe materials.
Table 38: Physical Properties of Common Pipe Materials
Material  Young’s Modulus (Ec)  Poisson’s Ratio, μ  
GN/m2  Glb/ft2  
Asbestos Cement  23 – 24  0.53 – 0.55  – 
Cast Iron  80 – 170  1.8 – 3.9  0.25 – 0.27 
Concrete  14 – 30  0.32 – 0.68  0.1 – 0.15 
Reinforced Concrete  30 – 60  0.68 – 1.4  – 
Ductile Iron  172  3.93  0.3 
PVC  2.4 – 3.5  0.055 – 0.08  0.46 
Steel  200 – 207  4.57 – 4.73  0.30 
The Flow Calculator category performs hydraulic calculations for the following elements: Circular Channel, Rectangular Channel, Triangular Channel, Trapezoidal Channel, Irregular Channel, and Pressurized Pipe.
Circular Channel
The circular channel dialog box is shown below.
Input for circular channel:
Output for circular channel:
Rectangular Channel
The rectangular channel dialog box is shown below.
Input for rectangular channel:
Output for rectangular channel:
Triangular Channel
The triangular channel dialog box is shown below.
Input for triangular channel:
Output for triangular channel:
Trapezoidal Channel
The trapezoidal channel dialog box is shown below.
Input for trapezoidal channel:
Output for trapezoidal channel:
Irregular Channel
The irregular channel dialog box is shown below.
Input for irregular channel:
Output for irregular channel:
The dialog box for irregular channel crosssection editor is shown below. The inputs are described above along with the irregular channels inputs.
Pressurized Pipe
The pressurized pipe calculator applies the energy equation between two points (points 1 and 2) and evaluates the outputs listed below. The pressurized pipe dialog box is shown below.
Input for pressurized pipe:
Output for pressurized pipe:
Discharge in channels and small streams can be conveniently measured by using a weir. Weirs can be categorized in to two: sharp crested and broad crested.
SharpCrested Weir
A sharpcrested weir is a vertical plate placed in a channel that forces the liquid to flow through an opening to measure the flow rate. The type of the weir is characterized by the shape of opening.
Rectangular SharpCrested Weir
A vertical thin plate with a straight top edge is referred to as rectangular weir since the cross section of the flow over the weir is rectangular (see the following figure).
The discharge equation for a rectangular weir is given as
where Q = discharge over the weir (m3/s, ft3/s)
h = head (m, ft)
L = weir length (m, ft)
C = weir coefficient
typically given as 1.84 in SI, 3.33 in English.
Flow through the weir may not span the entire width of the channel (L) due to end contractions. Experiments have indicated that the reduction in length is approximately equal to 0.1nh, where n is the number of end contractions (e.g., could be 2 in the contracted rectangular weir), and h is head over the crest of the weir as defined above. Therefore, the formula for contracted weir (one with flow contraction due to end walls) is given as
MultipleStep Sharp Crested Rectangular Weir
A multiple step weir is a rectangular weir with stepwise increase in length along the weir height. It helps to maintain low velocity across the weir during low flows and may be ecologically friendly as it allows fish freely pass across the weir.
The discharge equation for multistep weirs is given as:
where Q = discharge over weir (m3/s, ft3/s)
hi = head over the crest of the weir at step i (m, ft)
Li = length of the weir at step i (m, ft)
C = the flow coefficient (1.86 in SI, 3.367 in English)
Cipolletti SharpCrested Weir
The Cipolletti (or trapezoidal) weir has side slopes of 4 vertical to 1 horizontal ratio as shown in the figure below. The discharge equation for a Cipolletti weir is given as
where Q = discharge over weir (m3/s, ft3/s)
h = head (m, ft)
L = weir bottom length (m, ft)
C = the flow coefficient (1.86 in SI, 3.367 in English)
Notice that L is measured along the bottom of the weir (called the crest), not along the water surface.
VNotch SharpCrested Weir
With low flow rate, it is common to use a VNotch weir (shown below).
The discharge equation for a VNotch weir is given as
where Q = discharge over weir (m3/s, ft3/s)
h = head (m, ft)
θ = angle of notch (degree)
C = the flow coefficient that typically range between 0.58 and 0.62.
The most commonly used value of the notch angle θ is 90o; for this case (i.e., θ is 90o), C is found to be around 0.585.
Submerged SharpCrested Weir
The weir equations discussed above assume that the weir is free flowing. However, if the tailwater rises high enough, the weir will be submerged and the weir flowcarrying capacity will be reduced. Therefore, the discharge can be adjusted for submergence using the following equation:
where Qs = discharge over a submerged weir (m3/s, ft3/s)
Q = discharge computed using weir equations (m3/s, ft3/s)
hs = tailwater depth above the weir crest (m, ft)
h = head upstream of the weir (m, ft)
n = exponent, 1.5 for rectangular and Cipolletti weirs, 2.5 for a triangular weir.
BroadCrested Weir
If the weir is long in the direction of flow so that the flow leaves the weir in essentially a horizontal direction, the weir is a broadcrested weir.
The discharge equation for a broad crested weir is given as
where Q = discharge over weir (m3/s, ft3/s)
h = head (m, ft)
L = crest length (m, ft)
C = the flow coefficient that typically range between 2.4 and 3.087.
The flow coefficient C can be obtained from the following figure. Depending on the shape of the weir and head on the weir, the C value may range from 2.4 to 3.1.
BroadCrested Weir Discharge Coefficients (Adapted from Normann et al., 1985)
Generic Weir
Any other type of weirs can be modeled as generic weir using the following equation.
where Q = discharge over weir (m3/s, ft3/s)
h = head above weir crest (m, ft)
L = crest length (m, ft)
C = weir coefficient
The weir coefficient value depends on the weir type, and is the function of the head above the weir crest.
A Pump is used to augment head to the system (water distribution systems or waste water collection systems), and helps to lift water from low lying locations to a top of a hill or reservoir so that water could flow by gravity. The following figure shows an example pump configuration along with its corresponding energy and hydraulic grade lines (EGL and HGL).
Application of the energy equation between the water surfaces yields
where hp = head added by the pump (m, ft)
z = elevation with respect to a specified datum (m, ft)
hL = total head loss including friction and form losses (m, ft)
The term hp is more widely referred to as the system head, or total dynamic head, that must be overcome before fluid can be lifted by the pump. Since the magnitude of losses is directly proportional with the flow rate, Equation (17) indicates that for a given discharge, a unique system head is needed to maintain flow. The relationship is referred to as the system equation. Following, description of pump power calculation, pump characteristic curve, pump torque calculation and pump affinity laws is given.
Pump Power
The head supplied by a pump to the system can be converted to water power, or output power as follows.
where g = specific weight of water (9810 N/m3, 62.4 lb/ft3)
Q = pump discharge (m3/s, ft3/s)
hp = head added by the pump to the system (m, ft), see Equation (17)
Pwater = water power supplied by pump (KW, hp)
K = unit conversion factor (1000 in SI, 550 in English)
Water power will always be less than the power supplied to the pump shaft, often referred to as the brake power. Brake power is expressed as
where Pbrake = the power supplied to the pump (KW, hp)
= the efficiency of the pump motor (the ratio of power supplied to the pump to the energy converted
to actual power in the flow)
Pump Torque
The relationship between the water power supplied by a pump and the torque exerted by the impeller on the water is expressed as
where T = torque (KNm, lbfft)
w = pump speed in RPM
K = constant (9.55 in SI, and 5252 in English)
Pump Specific Speed
Pump specific speed (Nsp) is a dimensionless parameter used for preliminary selection of the type of pump that is most appropriate for a given application. The specific speed is defined as
where N = pump speed (rpm)
Q = flow rate (m3/s, gpm)
H = pump head (m, ft)
Pump Characteristic Curve
Pump characteristic curves are usually presented graphically describing the relationship between pump head, hp, and the flow rate, Q using either an exponential equation or 3point quadratic form. The exponential pump characteristic curve is given as
where hc = the pump cutoff head associated with the zero flow condition (m, ft)
Kp = resistance coefficient
b = flow exponent
nR = pump speed ratio (the ratio of the actual pump speed to the rated pump
speed); for constant speed pump operation, nR is equal to 1.
Given three hp–Q points [h_{c}, (h_{p}_{,1}, Q_{1}), (h_{p}_{,2}, Q_{2})], the pump curve can be calculated as
If a single rated capacity (hrated, Qrated) is given, two more points can be added to the curve by assuming a shutoff head at zero flow equal to 133% of the design head and a maximum flow at zero head equal to twice the design flow. Then, the curve can be treated as a threepoint curve.
The 3point quadratic type of pump characteristic curve is
where ap, bp, cp are the coefficients of the quadratic curve.
The coefficients are calculated as
If pump are constructed from impellers and casings that are geometrically similar (same shape but scale to different size), their pump curves will vary in a predictable manner. Similarly, altering the motor speed that is driving a particular pump will also have a predictable effect. The socalled affinity or similarity laws describe the relationship between the pump flow, head, and motor speed. Knowledge of these relationships will accelerate selecting a pump/motor combination for a particular application.
where Q = pump flow (Length3/Time)
n = pump speed (1/Time)
hp = pump head (Length)
D = impeller diameter Length)
Using the above equations, variable speed pumps can be directly modeled by fixing the impeller diameter.
System Head Curve
The ability to determine system head curves (sometimes called head capacity curves) is an essential task in the design of pumping systems. These curves are useful in determining the rating of the pumps and in assessing the number of pumps required and the type of drive to be used. Each curve describes the relationship between system head and capacity under identified conditions. More specifically, the curve represents the variation in total dynamic head against which the pumps will be required to operate under various flow conditions. The intersection of the system head curve (the resistance the pump must overcome) and the pump characteristic curve (head developed by the pump as a function of capacity) defines the point at which the pump will operate (see Figure below).
The solution of the energy equation gives the system curve as:
where
is the head loss in pipe 1,
is the head loss in pipe 2,
is the minor loss in pipe 1, and
is the minor loss in pipe 2.
If the HazenWilliams head loss expression and English units are used, this gives:
where
is the sum of the minor loss coefficients in pipe i.
Surge analysis is important to estimate the worstcase events in the Water Distribution Systems (WDS). Transient regimes in WDS are inevitable and will normally occur as a result of action at pump stations and control valves. Regions that are particularly susceptible to transients are high elevation areas, locations with either low or high static pressures, and regions far removed from overhead storage. They are generally characterized by fluctuating pressures and velocities and are critical precisely because pressure variations can be of high magnitude, possibly large enough to break or damage pipes or other equipment, or to greatly disrupt delivery conditions.
This section presents the calculation of potential surge using Joukowski equation, which is widely applied as a simplified surge analysis, and wave speed calculation. In the end, it provides the calculation of the inertia of pumps and motors, which are important for transients caused by pump failure.
Joukowski Expression
The pressure rise for instantaneous closure is directly proportional to the fluid velocity at cutoff and to the velocity of the predicted surge wave. Thus, the relationship used for analysis is simply the wellknown Joukowski expression for sudden closures in frictionless pipes
where
= surge pressure (m , ft)
= velocity change of water in the pipeline (m/s, ft/s)
c = wave speed (m/s, ft/s)
A = crosssectional area (m2, ft2 h)
g = gravitational acceleration (9.81 m/s2, 32.17 ft/s2)
Wave Speed
The wave speed, c, is influenced by the elasticity of the pipe wall. For a pipe system with some degree of axial restraint a good approximation for the wave propagation speed is obtained using
where Ef = elastic modulus of the fluid (for water, 2.19 GN/m2, 0.05 Glb/ft2)
ρ = density of the fluid (for water, 998 kg/m3, 1.94 slug/ft3)
Ec = elastic modulus of the conduit (GN/m2, Glb/ft2)
D = pipe diameter (mm, inch)
t = pipe thickness (mm, inch)
KR = coefficient of restraint for longitudinal pipe movement.
The constant KR takes into account the type of support provided for the pipeline. Typically, three cases are recognized with KR defined for each as follows (m is the Poisson’s ratio for the pipe material):
Case a: The pipeline is anchored at the upstream end only.
KR = 1 – m / 2
Case b: The pipeline is anchored against longitudinal movement.
KR = 1 – m2
Case c: The pipeline has expansion joints throughout.
KR = 1
The following table provides physical properties of common pipe materials.
Table 38: Physical Properties of Common Pipe Materials
Material  Young’s Modulus (Ec)  Poisson’s Ratio, μ  
GN/m2  Glb/ft2  
Asbestos Cement  23 – 24  0.53 – 0.55  – 
Cast Iron  80 – 170  1.8 – 3.9  0.25 – 0.27 
Concrete  14 – 30  0.32 – 0.68  0.1 – 0.15 
Reinforced Concrete  30 – 60  0.68 – 1.4  – 
Ductile Iron  172  3.93  0.3 
PVC  2.4 – 3.5  0.055 – 0.08  0.46 
Steel  200 – 207  4.57 – 4.73  0.30 
Inertia of Pumps and Motors
The combined inertia of pumps and motors driving them, including the connecting shafts and couplings, is required for transient analysis associated with the starting and stopping of pumps. The equations provided below are intended to be used as an initial guide to the inertia values that may be used as a reasonable first approximation, when more accurate data is not available. The total inertia for the pump/motor unit is the sum of both pump and motor inertias. The following inertia calculations are based on Thorley (2004).
Pump Inertias
From the linear regression analysis of 300 pump inertia data, two equations were developed for predicting the inertia I of pump impellers, including the entrained water and the shaft on which the impeller is mounted. The first equation represents the upper set of the data, and applies to single and doubleentry impellers, single and multistage, and horizontal and vertical, spindle machines.
where I = pump inertia (kg m2, lb ft2)
C1 = coefficients (0.03768, 0.6674)
P = power (kW, hp)
N = pump speed (rev/min)
The second equation is for lower set of the data and represents relatively small, singleentry, radial flow impellers of lightweight design. This is applied to relatively small pumps of lightweight design.
where C2 = coefficients (0.03407 in SI, 0.6244 in English)
Motor Inertias
Similar to pump inertia, linear regression of the motor inertia data yields the following equations.
where C3 = coefficients (0.0043 in SI, 0.0648 in English).
DarcyWeisbach friction factor, f, can be evaluated in terms of equivalent sand grain roughness, e, and Reynolds number, Re. Reynolds number is a dimensionless ratio of inertial forces to viscous forces acting on flow and is defined for any crosssectional shape as
For Re < 2,000, flow is referred to as laminar; if Re > 4,000, flow is generally turbulent. If Re is between 2,000 and 4,000, the flow is in a transitional region.
For laminar flows, the friction factor, f, is defined as
Numerous formulas exist to determine the friction factor. The two most popular equations are the ColebrookWhite (implicit) and the SwameeJain (explicit). The ColebrookWhite equation is
which must be solved iteratively. Swamee and Jain (1976) developed an explicit formula of the friction factor, f, for 4000 ≤ Re ≤ 108 (turbulent flow region) and 106 ≤ e/D ≤ 102 as
A cubic interpolation from the Moody diagram can be applied for the transitional flow range (2000 ≤ Re ≤ 4000) as
Procedure to find friction factor f
First, the relative roughness (e/D) and Reynolds number must be calculated. The Reynolds number is a function of kinematic viscosity of the fluid at the fluid’s temperature. Table 32 lists the kinematic viscosity for water over a range of temperature. Then, determine relative roughness of the pipe. Table 31 can be used as a guide to estimate equivalent sandgrain roughness for various types of pipes. Then, calculate the friction factor using either of the equations described above depending on the flow regime (i.e. laminar, transitional, or turbulent) based on the Reynolds number.
Table 32: Kinematic Viscosity of Water
Temperature  SI
(m2/s × 107) 
English
(ft2/s × 105) 

T(oC)  T(oF)  
0  32  17.7  1.91 
10  50  13.0  1.40 
20  68  10.1  1.09 
30  86  8.03  0.86 
40  104  6.58  0.71 
50  122  5.52  0.59 
60  140  4.72  0.51 
70  158  4.13  0.44 
80  176  3.65  0.39 
90  194  3.25  0.35 
100  212  2.95  0.32 
Source: Boulos et al. (2006)
Whenever flow velocity changes direction or magnitude in a conduit (e.g., at fittings, bends, and other appurtenances) added turbulence is induced. The energy associated with that turbulence is eventually dissipated into heat that produces a minor head loss, or local (or form) loss. The local (minor) loss associated with a particular fitting can be evaluated by
where V = mean velocity in the conduit (m/s, ft/s)
K = loss coefficient for the particular fitting involved.
The table given below provides the loss coefficients (K) for various transitions and fittings.
Table 33: Typical Minor Loss Coefficients
Source: Nicklow and Boulos (2005)
The methodology presented here for analysis and design of the drainage structures described in this section is based on HEC22 manual (FHWA, 2001)
Gutter Flow
Gutters are the sections of roadway that run adjacent to the curb. Their purpose is to collect and convey surface runoff to drainage inlets and in turn to underground storm sewers. The corresponding spread of water onto the pavement, or top width of flow measured perpendicular to the edge of the roadway, is a primary concern from an analysis perspective. The lateral cross slope of a traffic lane facilitates drainage of incident rainfall to the gutter. Depending on the cross slope, conventional gutters may be grouped as uniform gutter (i.e., has uniform cross slope) or composite gutters (i.e., has multiple cross slopes).
Uniform Gutter Sections
Uniform gutters have a shallow, triangular cross section, with a curb forming the nearvertical leg of the triangle as shown in the following figure.
The governing equation for uniform gutters is given as
where Q = gutter flow rate (m3/s, ft3/s)
Kc = empirical constant (0.376 in SI, 0.56 in English)
n = Manning’s roughness coefficient
Sx = gutter cross slope (m/m, ft/ft)
SL = longitudinal slope of the road way (m/m, ft/ft)
T = spread (m, ft)
Spread T is related to depth at the curb, d, and flow area, A, by
Table 37: Manning’s n for Street and Pavement Gutters
Type of Gutter or Pavement  Manning’s n 
Concrete gutter, troweled finish  0.012 
Asphalt Pavement:  
Smooth texture  0.013 
Rough texture  0.016 
Concrete gutterasphalt pavement:  
Smooth  0.013 
Rough  0.015 
Concrete pavement:  
Float finish  0.014 
Broom finish  0.016 
Adapted from FHWA (2001)
Composite Gutter Sections
Evaluation of composite gutters requires additional consideration of flow in the depressed section. The depression serves to retain more water above inlet entrances and thus increases gutter flow capacity. The relationship between total discharge, Q, and depressed gutter flow, Qw, can be expressed as
where Qw and Qs represent portion of the gutter flows for the sections shown in the figure above (m3/s, ft3/s).
The relationship between Q and Qs is given as
where Eo = ratio of Qw to Q, or
(71)
where W = width of the depressed section (m, ft)
Sw = cross slope of the depressed section (m/m, ft/ft)
The slope terms and the width of depression are related through depth of the depression, a, as
where a is the gutter depression (m, ft) illustrated in the figure given above.
Drainage Inlet
As flow accumulates in gutters and spread increases, the risk of traffic accidents and delays increases. To limit this risk, drainage inlets are needed at the edge of the roadway to intercept all or a portion of the runoff and convey it to an underground storm sewer. Although there are many types and sizes of inlets in use, they are generally classified as grate, curbopening, combination, or slotteddrain inlets. The responsibility of the designer is to determine the type, size, and spacing of inlets that costeffectively and safely captures runoff.
Key parameters in evaluating inlet flow conditions are capacity, Qi, and interception efficiency, E. The former refers to flow that is intercepted by a particular drainage inlet. Any gutter flow that is not intercepted is referred to as bypass, or carryover, flow, Qb. Thus, if Q is total gutter discharge,
The interception efficiency of the inlet is the fraction of gutter flow that the inlet will capture under a given set of conditions, and is expressed as
Inlets on Grade
Grate Inlet
A grate inlet, as shown in the figure below, consists of an opening in the gutter covered by one or more, flushmounted grates that are placed parallel to gutter flow.
Eo, defined as the ratio of frontal flow, Qw, to total gutter flow, Q, for a uniform gutter can be expressed as
where Qw = portion of flow that passes directly over the upstream side of the grate
W = width of the grade
The ratio of intercepted frontal flow to total frontal flow, also referred to as frontal flow efficiency, Rf, is defined as
where Kf = constant (0.295 in SI, 0.09 in English)
V = gutter flow velocity (m/s, ft/s)
Vo = splashover velocity (velocity where splashover first occurs) (m/s, ft/s).
The following figure could be used to determine splashover velocity based on grate type, length of the grate, and gutter flow velocity.
Charts to Determine SlashOver Velocity for Grate Inlets (Adapted from FHWA, 2001)
The ratio of side flow to gutter flow is expressed as
where Qs = gutter flow traveling around the perimeter of the grate when spread
exceeds its width (m3/s, ft3/s)
The ratio of intercepted side flow to total side flow, referred to as side flow efficiency, Rs, is defined as
where Ks = empirical constant (0.083 in SI, 0.15 in US)
L = grate length (m, ft) – The range of grate length allowed by H2OCalc is from 0.5 ft to 4.5 ft as defined in the FHWA Chart 5.
The overall inlet efficiency, E, can be evaluated from the frontal and side flow efficiencies by
From Equation (74), the capacity of a grate inlet can be obtained by multiplying Equation (79) by the total gutter flow, or
Curb Inlet
A curbopening inlet is comprised of a vertical opening in the curb that is covered by a concrete slab, as shown in the following figure.
For uniform cross slopes, the length of a curbopening inlet required to intercept all gutter flow, LT (m, ft), is defined as
where Ko = empirical constant (0.817 in SI, 0.6 in English).
The efficiency of shorterlength inlets can be evaluated by
where L = curbopening length (m, ft).
For the case where either locally or continuouslydepressed gutter sections are used (see the following figure), Equation (82) can still be used, but an equivalent cross slope, Se, should be substituted for Sx, where
where Eo = ratio of Qw to Q [see Equation (75)]
Sv = cross slope of the depressed section, expressed as Sv = a/W (see the following figure).
Slot Inlet
Slotted drain systems, illustrated in the figure given below, are comprised of a pipe that is cut longitudinally along its crown with bars placed perpendicular to support the opening. The hydraulic characteristics of slot inlet are similar to curb opening inlets; thus, Equations (81) and (82) are applicable.
Combination Inlet
Combination inlets integrate features of both curbopening and grate inlets (see the figure below). For equallength combination inlets, in which the grate and vertical curb opening are of the same length, inlet capacity and interception efficiency is not significantly different from that of the grate alone. Thus, Equations 75 through 80 are generally applicable.
Ditch Inlet
Roadside ditches may be drained by drop inlets similar to those used for pavement drainage. The ratio of frontal flow to total flow for trapezoidal ditches (channels) is expressed as
where W = width of the drop inlet (m, ft)
d = depth of flow in the channel (m, ft) determined using Manning’s equation.
Z = horizontal distance of side slope to a vertical rise of 1 unit (ft, m)
Frontal flow efficiency, side flow efficiency, total efficiency, intercepted flow, and bypass flow are computed using the technique described previously for grate inlets.
Inlets in Sag
Inlets in vertical curves, or sag locations, operate as weirs at shallow ponding depths and as orifices at larger depths. At intermediate depths, flow is not well defined and may actually fluctuate between weir and orifice control. The depth at which orifice flow begins depends on grate size and bar configuration, curb opening dimensions, or the slot width of an inlet.
Grate Inlets
The capacity under weir conditions is expressed as
where Pi = perimeter (m, ft) of the grate, not including the side adjacent to the curb, if present
Cw = weir coefficient (1.66 in SI, 3.0 in English)
d = depth at the curb (m, ft)
Under orifice conditions,
where Co = orifice coefficient (0.67)
Ag = clear opening, or effective area of the grate
g = gravitational constant (9.81 m/s2, 32.2 ft/s2)
Curb inlets
Curbopening inlets operate as weirs up to a depth (d) that is less than or equal to height (h) of the vertical opening. In this case, inlet capacity can be computed by
where Cw = weir coefficient (1.66 in SI, 3.0 in English)
L = curbopening length (m, ft)
If the gutter section is depressed, this relationship is modified as
where Cw = weir coefficient (1.25 in SI, 2.3 in English)
W = lateral width of depression (m, ft)
d = throat width (m, ft) measured from the undepressed cross slope
(i.e., d = TSx)
At depths of approximately 1.4 times the opening height, curbopening inlets tend to function as orifices. Under these conditions, capacity can be computed by
where do = effective head (m, ft) (see the following three figures)
h = throat width (m, ft) (see the following three figures)
(a) Horizontal Throat
(b) Inclined Throat
(c) Vertical Throat
Throat Configuration
Slot Inlets
Due to vulnerability to clogging, slotted drain inlets are not recommended for sag locations. Nevertheless, if they exist, slotted drains operate as weirs when depth at the slot is below approximately 0.2 ft (60 mm) and as orifices for depths greater than 0.4 ft (120 mm). Capacity of a slotted drain operating under weir conditions can be evaluated using Equation (87). The corresponding weir coefficient varies with flow depth and slot length, but a typical value is 1.4 in SI and 2.48 in English. Under orifice conditions, capacity is a function of the slot width, W, and is computed by
Combination Inlets
Combination inlets, especially those of a sweeper configuration, can be effective in sag locations. In this case, the sweeper inlet can extend from both sides of the grate. Similar to ongrade computations, under weir conditions, the inlet capacity of an equallength combination inlet is essentially equal to that of the grate alone. Under orifice conditions, the capacity increases to the sum of that of the grate (i.e., Equation 86) and that of the curb opening (i.e., Equation 89). For a conservative design, however, it is recommended that combination inlet be designed assuming complete clogging of the grate.
Ditch Inlets
Ditch inlets in sag intercept 100 % of the gutter flow.
A culvert is a pipe that carries water under or through some feature (usually a road or highway) that would otherwise block the flow of water. The culvert acts as an open channel as long as the flow is partly full. The characteristics of the flow are very complicated because the flow is controlled by many variables, including the inlet geometry, slope, size, roughness, approach and tailwater conditions, etc. Therefore, an adequate determination of the flow through a culvert is generally made by laboratory or field investigation.
Culverts are classified according to which of their ends controls the discharge capacity: inlet control or outlet control. If water can flow through and out of the culvert faster than it can enter, the culvert is under inlet control. If water can flow into the culvert faster than it can flow through and out, the culvert is under outlet control. Culverts under inlet control will always flow partially full. Culverts under outlet control can flow either partially full or full. H2OCalc analyzes culverts using two different approaches: a simplified culvert analysis method and the Federal Highway Administration’s (FHWA) HDS No. 5 method (Normann et al, 1985). Both techniques are described below.
Simplified Method
The simplified method classifies culvert flow into six different types on the basis of the type of control, the steepness of the barrel, the relative tailwater and headwater heights, and in some cases, the relationship between critical depth and culvert size. These parameters are quantified through the use of the ratios in Table 3.4. The six types are illustrated in the following figure.
For culverts flowing full, the friction loss (hf) can be determined using the Darcy formula. For partial flow, the Manning equation can be used. The friction head loss between sections 1 and 2 (see the figure below), for example, can be calculated from Manning’s equation as
where L = the culvert length
K = Conveyance factor and equals
R = hydraulic radius (m, ft); R = A/P
A = crosssectional area of flow section (m2, ft2)
P = wetted perimeter (m, ft)
N = Manning’s coefficient
Table 34: Culvert Flow Classification Parameters
Flow type  (h1–z)/D  h4/hc  h4/D  Culvert slope  Barrel flow  Location of control  Kind of control 
1  < 1.5  < 1.0  ≤ 1.0  steep  partial  Inlet  critical depth 
2  < 1.5  < 1.0  ≤ 1.0  mild  partial  outlet  critical depth 
3  < 1.5  > 1.0  ≤ 1.0  mild  partial  outlet  backwater 
4  > 1.0  > 1.0  any  full  outlet  backwater  
5  ≥ 1.5  ≤ 1.0  any  partial  inlet  entrance geometry  
6  ≥ 1.5  ≤ 1.0  any  Full  outlet  entrance geometry 
Adapted from Lindeburg (2003)
The total hydraulic head available, H, is divided between the velocity head in the culvert, the entrance loss (if considered), and the friction loss as follows
where ke is the local loss for entrance.
Rearranging Equations (46) and (48), velocity through the culvert can be given as
A. Type1 Flow
Water passes through the critical depth near the culvert entrance, and the culvert flows partially full. The slope of the culvert barrel is greater than the critical slope, and the tailwater elevation is less than the elevation of the water surface at the control section.
where Q = discharge from the culvert (m3/s, ft3/s)
Cd = discharge coefficient
v1 = average velocity of the water approaching the culvert entrance
α = velocityhead coefficient (i.e., assumed as 1.0)
dc = the critical depth
Ac = flow area at the critical section, not the culvert area
B. Type2 Flow
As in Type1 flow, flow passes through the critical depth at the culvert outlet, and the barrel flows partially full. The slope of the culvert is less than critical, and the tailwater elevation does not exceed the elevation of the water surface at the control section.
C. Type3 Flow
When backwater is the controlling factor in culvert flow, the critical depth cannot occur. The upstream water surface elevation for a given discharge is a function of the height of the tailwater. For Type3 flow, flow is subcritical for the entire length of the culvert, with the flow being partial. The outlet is not submerged, but the tailwater elevation does exceed the elevation of critical depth at the terminal section.
where A3 is the flow area at section 3 (i.e., the exit).
D. Type4 Flow
As in Type3 flow, the backwater elevation is the controlling factor in this case. Critical depth cannot occur, and the upstream water surface elevation for a given discharge is a function of the tailwater elevation. Discharge is independent of barrel slope. The culvert is submerged at both the headwater and the tailwater.
where Ao is the culvert area. The complicated term in the denominator corrects for friction. For rough estimates and for culverts less than 50 ft long, the friction loss can be ignored.
E. Type5 Flow
Partially full flow under a high head is classified as Type5 flow. The flow pattern is similar to the flow downstream from a sluice gate, with rapid flow near the entrance. Usually, Type5 flow requires a relatively square entrance that causes contraction of the flow area to less than the culvert area. In addition, the barrel length, roughness, and bed slope must be sufficient to keep the velocity high throughout the culvert.
F. Type6 Flow
Type6 flow, like Type5 flow, is considered a highhead flow. The culvert is full under pressure with free outfall.
Note that distance h3is undefined. For conservative first approximations, h3 can be taken as the barrel diameter.
The FHWA Method
The Federal Highway Administration (FHWA) offers equations as well as nomographs that can be used for analysis and design of culverts. Different equations and nomographs are developed for inlet controlled culvert flows and outlet controlled culvert flows. Only equation based analysis and design approaches are described in this section. Readers interested in the FHWA nomographs, for both control types, may refer to Normann et al. (1985).
Culvert design according to FHWA involves analyzing the culvert under both inlet control and outlet control conditions and selecting the control type that yields the worst condition (i.e., larger headwater depth). The design would be acceptable if the governing headwater depth is less than the maximum allowable headwater to avoid flooding of streets and property. Otherwise, the design needs to be revised (e.g., culvert size is increased) to reduce the headwater depth.
Inlet Control
The objective is to determine the headwater depth based on predetermined design discharge and a trial culvert size. The design equation used to determine headwater depth for inlet controlled culvert vary depending on the flow condition at the inlet of the culvert. If the inlet is submerged, the flow type would be orifice flow. Unsubmerged conditions will behave as a weir flow.
If the inlet is submerged (orifice flow), the equation to determine the headwater depth will be
where HWi = headwater depth above the inlet control section invert (ft)
D = diameter of the culvert (ft)
Q = discharge (ft3/s)
A = full crosssectional area of the culvert (ft2)
c, Y = constant from Table 3.5
Z = culver barrel slope term (ft/ft).
For mitered inlets,
and for all other conditions (i.e., inlet types other than mitered inlets),
The unsubmerged flow (weir flow) condition can be evaluated using one of the following two approaches:
1) Based on specific head (Hc) at critical depth
where Hc= specific head at critical depth (ft)
K and M = constants from Table 3.5
dc = critical depth (ft)
Vc =critical velocity (ft/sec)
2) A simpler form that ignores specific head (Hc) at critical depth
Table 35: Constants for Inlet Control Design Equations
Shape and material  Inlet Edge Description  K  M  c  Y 
Circular Concrete  Square edge w/ headwall  0.0098  2.000  0.0398  0.67 
Groove end w/ headwall  0.0078  2.000  0.0292  0.74  
Groove end projecting  0.0045  2.000  0.0317  0.69  
Circular CMP  Headwall  0.0078  2.000  0.0379  0.69 
Mitered to slope  0.0210  1.330  0.0463  0.75  
Projecting  0.0340  1.500  0.0553  0.54  
Circular Ring  Beveled ring, 450 bevels  0.0018  2.500  0.0300  0.74 
Beveled ring 33.70 bevels  0.0018  2.500  0.0243  0.83  
Rectangular Box  300 – 750 wingwall flares  0.0260  1.000  0.0385  0.81 
900 and 150 wingwall flares  0.0610  0.750  0.0400  0.80  
00 wingwall flares  0.0610  0750  0.0423  0.82  
Rectangular Box  450 wingwall flare  0.5100  0.667  0.0309  0.80 
180 – 33.70 wingwall flare  0.4860  0.667  0.0249  0.83  
Rectangular Box  900 headwall w/¾ in chamfers  0.5150  0.667  0.0375  0.79 
900 headwall w/ 450 bevels  0.7950  0.667  0.0314  0.82  
900 headwall w/33.70 bevels  0.4860  0.667  0.0252  0.87  
Rectangular Box  ¾ in chamfers, 450 skewed headwall  0.5220  0.667  0.0402  0.73 
¾ in chamfers, 300 skewed headwall  0.5330  0.667  0.0425  0.71  
¾ in chamfers, 150 skewed headwall  0.5450  0.667  0.0451  0.68  
450 bevels, 10450 skewed wall  0.4980  0.667  0.0327  0.75  
Rectangular Box, ¾ in. chamfers  450 non offset wingwall flares  0.4970  0.667  0.0339  0.80 
18.40 non offset wingwall flares  0.4930  0.667  0.0361  0.81  
18.40 non offset wingwall flares, 300 skewed barrel  0.4930  0.667  0.0386  0.71  
Rectangular Box, top bevels  450 wingwall flaresoffset  0.4970  0.667  0.0302  0.84 
33.70 wingwall flares – offset  0.4950  0.667  0.0252  0.88  
18.40 wingwall flares – offset  0.4930  0.667  0.0227  0.89  
Corrugated Metal Boxes  900 headwall  0.0083  2.000  0.0379  0.69 
Thick wall projecting  0.0145  1.750  0.0419  0.64 
Adapted from Normann et al. (1985)
Outlet Control
Headwater for outlet control conditions can be determined using energy equation based on tailwater depth and head loss through the culvert considering entrance loss, exit loss, and friction loss.
where H = total head loss (ft)
ke = entrance loss coefficient (see Table 3.6)
ho = water depth at the outlet of the culvert (ft)
dc = critical depth (ft)
q = unit discharge (discharge per unit width of the culvert) (ft3/s/ft)
Table 36: Entrance Loss CoefficientsOutlet Control, Full or Partly Full
Type of Structures and Design of Entrance  Coefficientke  
Pipe, Concrete  Mitered to conform to fill slope  0.7 
Endsection conforming to fill slope  0.5  
Projecting from fill, square cut end  0.5  
Headwall or headwall and wingwalls
Square Edge Rounded( radius= 1/12 Culvert Diameter Socket End of Pipe ( grooveend) 

0.5  
0.2  
0.2  
Projecting from fill, socket end (grooveend)  0.2  
Beveled edges, 33.70 or 450 bevels  0.2  
Side or slopetapered inlet  0.2  
Pipe, or PipeArch, Corrugated Metal  Projecting from fill ( no metal)  0.9 
Mitered to conform to fill slope, paved or unpaved slope  0.7  
Headwall or headwall and wingwalls squareedge  0.5  
Endsection conforming to fill slope  0.5  
Beveled edges, 33.70 or 450 bevels  0.2  
Side or slopetapered inlet  0.2  
Box, Reinforced Concrete  Wingwalls parallel ( extension of sides)
Square edge at crown 
0.7 
Wingwalls at 100250 or 300750 to barrel
Squareedged at crown 
0.5  
Headwall parallel to embankment (no wingwalls)
Squareedged on three edges Rounded on three edges to radius of 1/12 barrel dimension, or beveled edges on three sides 
0.5
0.2 

Wingwalls at 300750 to barrel
Crown edge rounded to radius of 1/12 barrel dimension, or beveled to edges 
0.2  
Side or slopetapered inlet  0.2 
Adapted from Normann et al. (1985)
InfoSWMM and InfoSWMM SA is a physically based, discretetime simulation model. It employs principles of conservation of mass, energy, and momentum wherever appropriate. This section briefly describes the methods InfoSWMM and InfoSWMM SA uses to model stormwater runoff quantity and quality through the following physical processes:
Transects refer to the geometric data that describe how bottom elevation varies with horizontal distance over the cross section of a natural channel or irregularshaped conduit. The following figure displays an example of a transect for a natural channel.
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 stationelevation data of a transect. InfoSWMM H2OMap SWMM InfoSWMM SA internally converts these data into tables of area, top width, and hydraulic radius versus channel depth. In addition, as shown in the diagram above, 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.
InfoSWMM H2OMap SWMM InfoSWMM SA can create transects from DEM or contour data. With contour data, the stations are taken at the contour lines. For DEM data, the total number of stations may be specified or else stations will be taken at a change in slope.
To extract a transect;
The following is a description of the part and use of the Transect Extractor:
Name  Description 
Source Data Format  Choose between contour and raster elevation data. 
Source Layer  Specify the layer containing elevation data. 
Elevation Field  Choose the field containing elevation values 
Transect ID  Choose the ID of the transect receiving the station / elevation information. 
Total Station  Specify the total number of stations for which to extract elevations. 
Add station when slope changed  Sample stations at each change in slope. 
Draw Line  Draw a line on the map from which to extract elevations. 
Transects refer to the geometric data that describe how bottom elevation varies with horizontal distance over the cross section of a natural channel or irregularshaped conduit. The Transect Editor is invoked whenever a new Transect object is created or an existing Transect is selected for editing.
To edit a transect;
It contains the following data entry fields:
Name  Description 
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. 
Manning’s N  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. For recommended values, refer to Manning’s N for Open Channels. 
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 

Maximum Depth  The maximum flow depth of the transect. This is automatically calculated from the elevations entered in the transect table. 
Note: Clicking the button will bring up a window that illustrates the shape of the transect cross section.
Each transect must be given a unique name. Conduits refer to that name to represent their shape. The maximum depth of the transect is calculated automatically and displayed in the transect editor. A special Transect Editor is available for editing the stationelevation data of a transect. Transects may be extracted from a digital elevation surface as well. InfoSWMM H2OMap SWMM InfoSWMM SA internally converts these data into tables of area, top width, and hydraulic radius versus channel depth. In addition, as shown in the diagram above, 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.
Note: Since this data is internally converted to area, top width, and hydraulic radius versus channel depth, only the relative elevations are important. This feature allows a transection to be extracted at any representative section along the channel reach without concern for absolute elevation.
If you have an InfoSWMM 2D license and you have set up your model with all of the necessary 2D elements and parameters, you can enable the 2D Simulation option. You must also set the 2D simulation options to fit the needs of your modeling scenario.
Name  Description 
Enable 2D Simulation  Select this option to enable 2D simulation 
2D Timestep Multiplier  The 2D timestep should be a multiple (i.e. 1, 2, 3 etc.) of the routing timestep specified in Time Step Options.
2D Timestep = Routing Timestep * 2D Timestep Multiplier The calculations used by the 2D simulation are partially explicit and they are therefore influenced by the simulation time step. The recommended timestep will vary according to the size of the mesh. For relatively large meshes, a timestep of 20 – 30 seconds would be appropriate, but for smaller meshes, 5 seconds or even less should be used. The results should be checked for mass balance errors and if necessary the timestep reduced. 
Velocity Tolerance  Mesh elements with water velocity below this value will have velocity reset to zero in terms of momentum calculations.
Typical value: 0 Default value: 0 
Maximum Velocity  Velocity threshold limiting the velocities that can be achieved in an element in a 2D simulation. Mesh elements with water velocity above this value will have velocity reset to the maximum specified.
Typical value: 33 ft/s (10 m/s) 
Inundation Mapping Depth Threshold  Depth threshold used to determine Time to first inundation for mesh elements. Time to first inundation is reported as the time (from the start of the simulation) at which water depth in the mesh element first exceeds this threshold.
Default value: 0.03 ft (0.01 m) 
Depth Tolerance  The Depth Threshold is used to determine whether to consider a mesh element wet or dry. Mesh elements with depth of water below this value will be considered dry and a zero depth will be displayed in the output results. Only mass conservation will be considered in elements with depth below this threshold
Typical value: 0.003 ft (0.001 m) Default value: 0.003 ft (0.001 m) 
Momentum Tolerance  Depth threshold used to determine whether to consider momentum in a mesh element or not. Movement of water will not be calculated for mesh elements with depth of water below this value; only mass conservation will be taken into account.
Typical value: 0.0030.03 ft (0.0010.01 m) Default value: 0.03 ft (0.01 m) 
Timestep Stability Control  This parameter ensures that the internal timestep used by the 2D engine is within the stability bounds given by the CFL condition ( Courant Friedrichs LewyCourant R. Friedrichs K.O. and Lewy H. (1928) On the partial Difference Equations of Mathematical Physics. Math. Ann., Vol 100, p32. condition). Valid value: 0 < TSC < 1 Typical value: 0.95 
Theta  Weighting factor, θ, for the semiimplicit parameter. Weights the explicit and semiimplicit parts of the numerical scheme used for the time integration of the flow equations. The higher the value, the more weight given to the implicit part.
Valid values: 0 < θ < 1 Typical value: 0.9 
A unit hydrograph is defined as the direct runoff hydrograph resulting from a unit depth of excess (effective) rainfall produced by a storm of uniform intensity and specified duration. Unit hydrographs could be natural or synthetic. Natural unit hydrographs are derived from observed data, whereas synthetic unit hydrographs are generated following empirical techniques based on watershed parameters and storm characteristics to simulate the natural unit hydrograph. In addition to the rational formula, H2OCalc computes peak flow from a watershed using the NRCS (SCS) dimensionless unit hydrograph.
The NRCS dimensionless unit hydrograph, graphically descried below, is widely used in practice. To generate a trhour unit hydrograph for a watershed, time to peak (Tp) and the peak flow rate (Qp) are determined using watershed characteristics.
where tr is duration of effective rainfall, and tl is lag time of the watershed. Lag time represents the time from the center of mass of effective rainfall to the time to peak of a unit hydrograph. In other words, lag time is a delay in time, after a brief rain over a watershed, before the runoff reaches its peak. The lag time can either be specified by the user, or can be calculated by the model using the following SCS equation.
where tl = lag time of the watershed (hr).
L = hydraulic length of the watershed (ft). This refers to travel distance of water from the most upstream location of the watershed to the point where the unit hydrograph is derived.
CN = the SCS curve number. This is a measure of runoff generating capacity of a watershed, and it depends on the soil, the antecedent moisture condition, the cover, and the hydrologic conditions of the watershed. Recommended CN values are given in the following table for urban areas (USDA 1986). The SCS suggests the CN values for the above equation to be within 50 and 95.
S = average slope of the watershed.
The peak flow rate is calculated as:
where Qp = peak flow rate (ft3/s).
A = area of the watershed, in square miles, draining to the location of the unit hydrograph.
Tp = time to peak of the unit hydrograph in hours.
Once Tp and Qp are known, actual time and flow rate ordinates of the trhour unit hydrograph are determined by multiplying the dimensionless time (T/Tp) and the dimensionless flow rate ordinates (Q/Qp) by Tp and Qp, respectively.
NRCS Dimensionless Unit Hydrograph
Storm hydrograph could be computed using the unit hydrograph and a given precipitation pattern. The precipitation could be a design precipitation or actual (i.e., historical precipitation). A design precipitation may be specified in the form of rainfall depth over 24hr duration. Distribution of the rainfall depth across the 24hour can be estimated using the SCS (NRCS) rainfall types (i.e. Type I, Type IA, Type II and Type III) shown in the following figure.
SCS (NRCS) Rainfall Types (Source Nicklow et al., 2006)
Rules for Entering the SCS CN in the Dialogs
The rules are listed below but in paragraph style. The program will use the TC and SCS CN from the Subcatchment table to calculate the UH from the Rainfall Excess. The Rainfall Excess is calculated from the Soils DB Table using the Soils Coverage in the Infiltration Tables. If you do not have a Soils Table and an Infiltration Coverage Table the program will make the Rainfall Excess equal to the Rainfall and you will not have any Infiltration Losses. The default value for Initial abstraction from IA = 0.2 * (1000/CN 10)
Rule 1. The Column NRCS CN in the Subcatchment Table is the CN used in the Unit Hydrograph Routing
Rule 2. If the Column TC in the Subcatchment Table is Blank then the program will estimate TC in minutes from the Slope and other parameters
Rule 3. Use Default as the Infiltration Model for consistency in the Subcatchment Table.
Rule 4. If the Depression Storage for the UH is 0.0 then the initial abstraction for the UH Is calculated from the CN in the Subcatchment Table
Rule 5. The CN for the Soil is entered in the Soil DB Table
Rule 6. The Soil coverage for each Subcatchment is entered in the Infiltration DB Table and the program will calculate the weighted by area infiltration CN
Rule 7. Use a Runoff Model of NRSCS UH and an Infiltration model of CN in Run Manager
Rule 8. The TC and UH CN are listed in the output report file of InfoSWMM H2OMap SWMM
Infiltration is the process of rainfall penetrating the ground surface into the soil over the pervious areas of Subcatchments.
InfoSWMM H2OMap SWMM InfoSWMM SA offers three choices for modeling infiltration:
Horton’s Equation
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, as shown in the following figure.
Horton’s infiltration equation is given as
Input parameters required by this method include the maximum (fi) and minimum (f∞) infiltration rates, a decay coefficient (α) that describes how fast the rate decreases over time, and a regeneration constant that describes the restoration of infiltration rate during dry periods (αd). The regeneration equation is given as
“Horton’s method is empirical in nature and is perhaps the best known of the infiltration equations. Many hydrologists have a “feel” for the best values of its three parameters despite the fact that little published information is available. In its usual form it is applicable only to events for which the rainfall intensity always exceeds the infiltration capacity; however, the modified form used in SWMM is intended to overcome this limitation. The Horton method has been a part of SWMM since the program was first Release (Metcalf and Eddy et al., 1971a).” (Source EPA – Storm Water Management Model Reference Manual Volume I – Hydrology EPA/600/R15/162 July 2015 )
“A. O. Akan developed a modified version of the Horton infiltration method (Akan, 1992; Akan and Houghtalen, 2003) that has been added as a separate infiltration option in SWMM 5. The method uses the same parameters as the original Horton method but instead of tracking the time along the Horton decay curve it uses the cumulative infiltration volume in excess of the minimum infiltration rate as its state variable. It assumes that part of the infiltrating water will percolate deeper into the soil at the minimum infiltration rate (commonly taken as the soil’s saturated hydraulic conductivity). As a result, it is the difference between the actual and minimum infiltration rates that accumulates just below the surface that causes infiltration capacity to decrease with time. This method is purported to give more accurate infiltration estimates when low rainfall intensities occur ” (Source EPA – Storm Water Management Model Reference Manual Volume I – Hydrology EPA/600/R15/162 July 2015 )
GreenAmpt Method
The GreenAmpt equation is a physicallybased model which can give a good description of the infiltration process. 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 GreenAmpt equation (Green and Ampt, 1911) has received considerable attention in recent years. The originalequation was for infiltration with excess water at the surface at all times.Mein and Larson (1973) showed how it could be adapted to a steady rainfall input and proposed a way in which the capillary suction parameter could be determined. Chu (1978) has shown the applicability of the equationto the unsteady rainfall situation, using data for a field catchment. The GreenAmpt method was added into SWMM III in 1981 by R.G. Mein and W. Huber (Huber et al., 1981).” (Source EPA – Storm Water Management Model Reference Manual Volume I – Hydrology EPA/600/R15/162 July 2015 )
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, the soil’s hydraulic conductivity (used to estimate a minimum separation time for distinct rain events), and a regeneration constant that describes the restoration of infiltration capacity during dry periods.
“The Curve Number infiltration method is new to SWMM 5. It is based on the widely used SCS (Soil Conservation Service, now known as the NRCS – Natural Resource Conservation Service) curve number method for evaluating rainfall excess. First developed in 1954, the method is embodied in the widely used TR20 and TR55 computer models (NRCS, 1986) as well as most hydrology handbooks and textbooks (e.g., Bedient et al., 2013). It was added into SWMM to take advantage of its familiarity to most practicing engineers and the availability of tabulated curve numbers for a wide range of land use and soil groups. The original curve number method is a combined loss method that lumps together all losses due to interception, depression storage, and infiltration to predict the total rainfall excess from a rainfall event. The SWMM uses a modified, incremental form of the method that accounts only for infiltration losses, since the other abstractions are modeled separately. Other incremental applications of the curve number method have been proposed by Chen (1975), Aron et al. (1977) and Akan and Houghtalen (2003).” (Source EPA – Storm Water Management Model Reference Manual Volume I – Hydrology EPA/600/R15/162 July 2015 )
InfoSWMM and InfoSWMM SA is a comprehensive GIScentric, highly advanced hydrologic, hydraulic, and water quality simulation model that could be used for the management of urban stormwater and wastewater collection systems. InfoSWMM and InfoSWMM SA represents the stateoftheart in GISbased sanitary and storm sewer collection systems analysis. The program provides scores of cutting edge simulation capabilities for performing a wide variety of essential modeling tasks in record time. It helps engineers predict the response of the sewer collection system to various flow loads and physical conditions.
Physical Components  NonPhysical Components 
Hydraulic Simulation (Transport) Model  Water Quality Modeling 
Stormwater Modeling  Sewer Modeling 
InfoSWMM InfoSWMM SA is a fully dynamic wastewater and stormwater modeling and management software application. InfoSWMM InfoSWMM SA can be used to model the entire land phase of the hydrologic cycle as applied to urban stormwater and wastewater collection systems. The model can perform single event or longterm (continuous) rainfallrunoff simulations accounting for climate, soil, land use, and topographic conditions of the watershed. In addition to simulating runoff quantity ,InfoSWMM InfoSWMM SA can also predict runoff quality including buildup and washoff of pollutants from primarily urban watersheds. Once runoff quantity and quality is simulated, and wastewater loads at receiving nodes are determined, the routing portion of InfoSWMM InfoSWMM SA transports using either steady flow routing, kinematic wave routing or dynamic wave routing, the flow through a conveyance system of pipes, channels, storage/treatment devices, pumps, and hydraulic regulators such as weirs and orifices. The model offers advanced RealTime Control (RTC) scheme for the operational management of hydraulic structures.
This section describes how InfoSWMM InfoSWMM SA models the physical objects composing a sewer collection system as well as its operational parameters and the computational methods used to simulate its hydrologic, hydraulic, and water quality behaviors.
InfoSWMM InfoSWMM SA conceptualizes a drainage system as a series of water and material flows between several major environmental compartments. These compartments and the InfoSWMM InfoSWMM SA objects they contain include:
· The Atmosphere compartment, from which precipitation falls and pollutants are deposited onto the land surface compartment. InfoSWMM InfoSWMM SAuses 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 Transportcompartment.
· 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 userdefined hydrographs. The components of the Transport compartment are modeled with Node and Link objects.
Not all compartments need to appear in a particular InfoSWMM InfoSWMM SA model. For example, one could model just the transport compartment, using predefined hydrographs as inputs.
The Three Main Components are:
1. Arc Map Table of Contents (TOC),
2. InfoSWMM Menus
3. InfoSWMM Attribute Browser (AB)
Clark’s method derives a unit hydrograph by explicitly representing the processes of translation and attenuation, which are the two critical phenomena in transformation of excess rainfall to runoff hydrograph. Translation refers to the movement, without storage, of runoff from its origin to the watershed outlet in response to gravity force, where as attenuation represents the reduction of runoff magnitude due to resistances arising from frictional forces and storage effects of soil, channel, and land surfaces. Clark (1945) noted that the translation of flow through the watershed could be described by a timearea curve (see Figure below), which expresses the curve of the fraction of watershed area contributing runoff to the watershed outlet as a function of travel time since the start of effective precipitation. Each subarea is delineated so that all the precipitation falling on the subarea instantaneously has the same time of travel to the outflow point.
Developing a timearea curve for a watershed could be a time consuming process. For watersheds that lack derived timearea diagram, the HECHMS model, which was developed at the Hydrologic Engineering Center (HEC) of the U.S. Army Corps of Engineers, uses the following relationship (HEC, 2000)
where Ac,t is cumulative watershed area contributing at time t; AT is total watershed area; and tc is time of concentration of the watershed. If the incremental areas, denoted as Ai in the figure below, are multiplied by a unit depth of excess rainfall and divided by Δt, the computational time step, the result is a translated hydrograph that is considered as an inflow to a conceptual linear reservoir located at the watershed outlet.
To account for storage effects, the attenuation process is modeled by routing the translated hydrograph through a linear reservoir with storage properties similar to those of the watershed. The routing model is based on the mass balance equation
where dS/dt is time rate of change of water in storage at time t; It is average inflow, obtained from the timearea curve, to storage at time t; and Qt is outflow from storage at time t.
For linear reservoir model, storage is related to outflow as
where R is a constant linear reservoir parameter that represents the storage effect of the watershed. Usually, lag time (tL) is used as an approximation to R. Combining and solving Equations 116 and 117 using a finite difference approximation provides
where C1 and C2 are routing coefficients calculated as
The average outflow during period t is
If the inflow, It, ordinates are runoff from a unit depth of excess rainfall, the average outflows derived by Equation 121 represent Clark’s unit hydrograph ordinates. Clark’s unit hydrograph is, therefore, obtained by routing a unit depth of direct runoff to the channel in proportion to the timearea curve and routing the runoff entering the channel through a linear reservoir. Note that solution of Equations 118 and 121 is a recursive process. As such, average outflow ordinates of the unit hydrograph will theoretically continue for an infinite duration. Therefore, it is customary to truncate the recession limb of the unit hydrograph where the outflow volume exceeds 0.995 inches or mm. Clark’s method is based on the premise that duration of the rainfall excess is infinitesimally small. Because of this, Clark’s unit hydrograph is referred to as an instantaneous unit hydrograph or IUH. In practical applications, it is usually necessary to alter the IUH into a unit hydrograph of specific duration. This can be accomplished by lagging the IUH by the desired duration and averaging the ordinates.
The Scenario Explorer is an essential feature that enables the user to create, edit, modify, run, and compare any number of “what if” modeling scenarios with little extra effort. InfoSWMM H2OMap SWMM InfoSWMM SA ‘s Scenario Explorer has a treetype structure (i.e. stem and branches) allowing the scenarios to inherit facilities (data elements) and modeling data from the parent scenario using the principle of inheritance thus greatly simplifying the additional effort required to manage and create various modeling conditions. Each project “child” scenario inherits the information from its “parent” scenario. Therefore, the Scenario Explorer enables you to maintain a single model of your collection system and quickly develop and evaluate numerous modeling alternatives to support your capital improvement decisions.
For example, from the same model, you could create different modeling scenarios for dryweather conditions and wetweather conditions by changing inflow data only. Likewise, if you need to evaluate the effect of adding some more network components (e.g., junctions and conduits) to mimic your city’s future growth, all you need to do is add those network components and their associated data. You could evaluate the effect of changing a conduit shape and size, pump status or control, weir and/or orifice setting, external inflows, Subcatchment properties, storage shape and size, and many others properties and their combinations on your drainage (collection) system. You can easily switch between scenarios and compare modeling results instantly. You can even go to the extent of directly extracting (cutting) one or more sewersheds from the main model (Base Scenario) and analyze only those sewersheds, as well as, merge together any number of models for detailed analyses using the scenario Explorer.
In summary, scenarios in InfoSWMM H2OMap SWMM InfoSWMM SA may be used for the following:
In InfoSWMM H2OMap SWMM InfoSWMM SA , a scenario is defined in terms of the following three classes of modeling data:
Four tools provide access to the power of scenario management. Click on the links below for more information:
NOTE: Data Elements deleted from one scenario will be deleted in all related scenarios and the Base Scenario. Please use the Facility Manager and Query Set functionality to disable the facilities you would not like to appear or operate in an inherited data set.
Each of three components of a scenario can be further defined as follows:
The External page on the Inflows Editor dialog is used to specify time series of direct external inflow and pollutant inflows entering a node of the drainage system.
To initiate the External Inflow editor, do one of the following:
· To edit external inflow for one node at a time:
o Select node, click on the icon located at the second row of the top of the attribute browser, and then select Inflow from the initiated pop up menu. This will initiate the following External Inflow Editor.
Note: Once external inflow properties are specified, the user needs to click on the button to save the properties or on the or buttons to cancel the changes and close the editor.
2. To edit external inflow for multiple nodes at a time:
· Select one of the group editing features (i.e., Group Editing on Selection () or Group Editing on Domain ()).
· On the initiated Group Editing dialog, click on button. These steps would activate the External Inflow Editor shown below.
Note:
· Once external inflow properties are specified, the user needs to click on the button to save the properties or on the or the buttons to cancel the changes. Select the button to close the editor.
· The button deletes external inflow data for the selected elements only. The button empties external inflow data for all nodes, not just the selected nodes, in the drainage system.
The properties listed in the editors are as follows:
Name  Description 
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 constituents’ inflow. For FLOW, the units are the projects’ flow units. For Pollutants, the units are the pollutants’ concentration units if inflow is a concentration, or can be any mass flow units if the inflow is a mass inflow (see Conversion Factor below). If left blank, no baseline inflow is assumed. 
Baseline Pattern  The optional Baseline Time Pattern can be used to apply a periodic adjustment to the baseline inflow value by month of the year or day of the week. 
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 constituents’ inflow time series. The baseline value is not adjusted by this factor. The scale factor can have several uses, such as changing the magnitude of the inflow hydrograph while keeping its’ shape the same, without having to reedit the entries in the inflow time series. This factor can also 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 concentrations or mass flows. This input is not required if the constituent is Flow. 
Pollutant Mass Conversion Factor  Numerical conversion factor used to convert a pollutant mass flow rate in the time series data into (concentration x flow) units used by the project. For example, if the time series data were in pounds per day and the pollutant concentration defined in the project was mg/L while the flow units for the project were CFS, then the conversion factor value would be 454,000 mg/lb / 86400 sec/day = 5.25. 
Note:
The Groundwater Editor dialog is used to specify the groundwater property of a Subcatchment. 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 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 heads:
where
Qgw = groundwater flow (cfs per acre or cms per hectare)
Hgw = elevation of groundwater table (ft or m)
Hsw = elevation of surface water at receiving node (ft or m)
E = elevation of node invert (ft or m)
To initiate the Groundwater editor, do one of the following:
1. To edit Groundwater inputs for one Subcatchment at a time:
o Select Subcatchment, click on the icon located at the second row of the top of the attribute browser, and then select Groundwater from the initiated pop up menu. This will initiate the following editor.
Note: Once groundwater properties are specified, the user needs to click on the button to save the properties or on the or button to cancel the changes and close the editor.
2. To edit Groundwater inputs for multiple Subcatchments at a time:
· Select one of the group editing features (i.e., Group Editing on Selection () or Group Editing on Domain ()).
· On the initiated Group Editing dialog, click on . These steps would activate the Groundwater Editor shown below.
Note:
· Once groundwater properties are specified, the user needs to click on the button to save the properties, or on the or the buttons to cancel the changes, the button to close the editor.
· The button deletes groundwater data for the selected Subcatchments only. The button empties groundwater data for all Subcatchments, not just the selected ones, in the drainage system.
The properties listed in the editor are as follows:
Name  Description 
Aquifer Name  Name of aquifer object that supplies groundwater. 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 sits above the aquifer (ft or m). 
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. 
SurfaceGW Interaction Coefficient  Value of A3 in the groundwater flow formula. 
Fixed Surface Water Depth  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). 
Threshold Groundwater Elevation  The aquifer water table elevation which must be reached before any ground water flow occurs (feet or meters). The default setting when the field is left blank is the receiving node’s invert elevation. 
Note
The database tools submenu is provided to assist the user in database management. InfoSWMM H2OMap SWMM InfoSWMM SA project is grounded upon the linkage between graphical network representation and external databases. Unfortunately, the data contained in those databases may, at times, get corrupted and therefore, may require maintenance due to forces beyond the control of the user. These database maintenance functionality is offered by the database tools submenu.
To run database maintenance, from the InfoSWMM H2OMap SWMM InfoSWMM SA Utilities menu, select Database. There you may select from any of the following options. You may click on the following links to learn more about their specific functionality.
Critical Model Recovery: If you have Map issues such as disappearing pipes or nodes when using Mapping Display then this sequence of DB tools will help you with your mapping issues.


The relationship between the Various InfoSWMM H2OMap SWMM InfoSWMM SA Versions and SWMM5
The relationship between ICM, ICM SE, InfoSWMM, InfoSewer, H2OMap Sewer, and SWMM5. InfoSWMM can import H2OMap SWMM, SWMM5, H2OMap Sewer, InfoSewer can export to ICM_SE or ICM using the SWMM5 data format. Innovyze products that either run the current SWMM5 engine or imports and exports the current SWMM5 data files are (click to see the associated product page in each row in the following table for each product or go to www.innovyze.com for all Innovyze products.
InfoSWMM Suite based on EPA SWMM 5.1.011 GA generated RTK, SWMM5 Hydrology, SWMM5 Infiltration, SWMM5 RDII, SWMM5 SuDS/LID parameters can also be used in ICM and ICM SE 
InfoSWMM Sustain based on EPA SWMM 5.1.011 Optimized LID Controls can also be used with ICM SuDS 
InfoSWMM SFEM based on EPA SWMM 5.1.011 generated DWF can be used in ICM SE and ICM 
InfoSWMM 2D based on EPA SWMM 5.1.011 
InfoSWMM RDII Analyst based on EPA SWMM 5.1.011 GA generated RTK parameters can also be used with ICM and ICM SE RDII 
H2OMap SWMM Suite based on EPA SWMM 5.1.011 GA generated RTK, SWMM5 Hydrology, SWMM5 Infiltration, SWMM5 RDII, SWMM 5 SuDS/LID parameters can also be used in ICM and ICM SE 
H2OMap SWMM RDII Analyst based on EPA SWMM 5.1.011 GA generated RTK parameters can also be used with ICM and ICM SE RDII 
SWMMLive based on EPA SWMM 5.1.011 has the ICM LIve GUI with the InfoSWMM Engine 
InfoWorks ICM Imports and exports EPA SWMM 5.1.011 has SWMM5 Hydrology, SWMM5 Infiltration, SWMM5 RDII, SWMM 5 SuDS/LID 
InfoWorks ICM SE Imports and exports EPA SWMM 5.1.011 has SWMM5 Hydrology, SWMM5 Infiltration, SWMM5 RDII, SWMM 5 SuDS/LID 
How InfoSWMM and H2OMap SWMM, InfoSWMM SA import and export SWMM 5 files
The history of the Low Impact Development (LID) features and FEMA approval for SWMM 5 from Wikipedia
InfoSewer and H2OMap Sewer do not import SWMM 5 but there is a good connection between InfoSewer and InfoSWMM and then via InfoSWMM Export to SWMM 5
InfoSWMM SA Import Options (in addition to SWMM5 Import)
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.
To initiate the Dry Weather Inflow editor, do one of the following:
1. To edit dry weather inflow for one node at a time:
§ Select node, click on the icon located at the second row of the top of the attribute browser, select Inflow from the initiated pop up menu, and then click on Dry Weather button. This will initiate the following Dry Weather Inflow editor.
§ Use to add more rows to the table or to delete the highlighted rows.
Notes:
Weekend (a weekend pattern is only applied to Saturday and Sunday, otherwise the multiplier value is 1.0 for weekdays) If multiplier patterns are specified then the flow into the node at any given timestep is (Average DWF * Monthly Multiplier * Daily Multiplier * Hourly Multiplier * Weekend Multiplier)
2. To edit dry weather inflow for multiple nodes at a time:
· Select one of the group editing features (i.e., Group Editing on Selection () or Group Editing on Domain ()).
· On the initiated Group Editing dialog, click on button, and then click on Dry Weather button. These steps would activate the Dry Weather Inflow Editor shown below.
Note:
The Dry Weather Inflow dialog consists of the following input fields:
Name  Description 
Constituent  Selects the constituent (FLOW or one of the project’s specified pollutants) whose dry weather inflow will be specified. 
Allocation Code  An ID used to distinguish the types of dry weather flows (e.g. Residential, Industrial, etc.) 
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 week days and week ends). 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. 
Note: More than one constituent can be edited while the dialog is active by simply selecting another choice for the Constituent property.
DWF Allocator (available with Suite license level):
An indispensable master planning tool, InfoSWMM DWF Allocator gives you seven highly advanced and efficient geospatial methods for processing geometric polygons to accurately compute and load network models based on load type, location, and variation:
· Geocoded meter billing data (meter consumption database)
· Polygon Intersection – spatial intersection of multiple polygon layers
· Polygon Extraction – spatial summation of load category area polygon
· Closest (Nearest) Junction Method
· Closest (Nearest) Conduit Method
· Meter – Junction Allocation
· Meter – Conduit Allocation
The Query Summation Report may be used in conjunction with DB Queries to determine and evaluate the different attributes associated with the InfoSWMM H2OMap SWMMInfoSWMM SA data elements (Subcatchments, Junctions, Outfalls, Dividers, Storage Units, Conduits, Pumps, Orifices, Weirs, and Outlets) that satisfy the DB query.
Click the following links to learn more:
Description of Query Summation Report dialog and Report tab
The example below contains parameters that enable a summary of total conduit length by Geom1 (diameter etc.).
Contents of the Query Summation Report dialog are described below.
Name  Description 
ID  Specify the ID of the Query that you want to evaluate in your Query Summation Report. 
Summary Field  Choose the Summary Field here. Use this to identify the Summary Class Field values. Depending on the DB Query ID chosen, all the fields corresponding to the DB Query element type will be available. 
Summary Class Field  Use this field to select the InfoSWMM data field summary that you want to see. The Query Summation Report will display all the selected Summary Class Field values in your Summary Report. 
SubTotal  The Summary Class Field values for your Summary Field is displayed here. For instance if your Summary Class Field is GEOM1then all the diameter values will be displayed here. 
SubClass  The data field values for your Summary Field is displayed here. For instance if your Summary Field is ID then all the element IDs will be displayed here. The SubTotal section of the Summation Report will display all the Class Field values corresponding to this element. 
Refresh  Use this to refresh your Query Summation dialog box. Change the Query ID and choose the Summary Field and the Summary Class Field and click on the Refresh button to display the new results. 
Close  Use this to close out of the Query Summation dialog box. 
Note: The Customized Report Manager can now be accessed from the Report Manager by pressing the down arrow next to the new button.
Query Summation Report Methodology
Do the following to launch a Query Summation Report –
The following example shows the data from the example above in a bar chart format
Note: Rightclick inside the chart to initiate the Graph Control dialog
The following example shows the data from the example above in a pie chart format:
Note: Rightclick inside the chart to initiate the Graph Control dialog
Adjusting display of Bar and Pie Charts
The display of the Bar and Pie charts can be controlled with the Graph Control dialog. To initiate the Graph Control dialog, click on the properties dialog. The following dialog will appear:
Like all other visual data objects, Weir object is edited using the attribute browser.
To edit attributes of a weir:
(ID) – Userassigned weir name.
Description – Optional description of the weir. Start Node – Name of node on the inlet end of the weir (which is normally the end at higher elevation). End Node – Name of node on the outlet end of the weir (which is normally the end at lower elevation). Weir Type – Weir type. Available options are:
Height – Vertical height of weir opening (feet or meters). Weir Length – Horizontal length of weir opening (feet or meters). Trapezoidal Weir Side Slope – Slope (widthtoheight) of side walls for a VNOTCH or TRAPEZOIDAL weir. Weir Crest Height – Height of bottom of weir opening from invert of inlet node (feet or meters). Coefficient of Discharge – 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). Typical values are:
Weir with Flap Gate – YES if the weir has a flap gate that prevents backflow, NO if it does not. Number of End Contractions – Number of end contractions for a TRANSVERSE or TRAPEZOIDAL weir whose length is shorter than the channel it is placed in. Either 0, 1, or 2 depending on if no ends, one end, or both ends are beveled in from the side walls. Trapezoidal Weir Discharge Coefficient – Discharge coefficient for flow through the triangular ends of a TRAPEZOIDAL weir. See the recommended values for Vnotch weirs listed above. Open Top – Yes or No for a Weir in InfoSWMM If Open Top is NO then the weir can surcharge and flow can increase in the weir until the upstream node is flooded. This is the same as a Can Surcharge of YES in EPA SWMM 5.1+ If Open Top is YES then the weir does not surcharge and flow does not increase in the weir when the weir is full. This is the same as a Can Surcharge of NO in EPA SWMM 5.1+
ROADWAY WEIR Road Surface Type of road surface: PAVED or GRAVEL. Initial Status – Helps to specify the Setting of the weir at the simulation start time. Click the button to initiate the Initial Status editor. Control – Helps to supply simple weir operational control rule. Click the button to initiate the Simple Control Rule. In addition, a more sophisticated RealTime Control Rule for operational control of weir could be formulated using the RealTime Control Rule editor. Tag – Optional label used to identify or categorize the weir. Installation Year – Optional. The year the weir is installed. Retirement Year – Optional. The year the weir will be retiring. Zone – Optional zone to which the weir belongs. Phase – Optional phase of the project. 
Tools Menu – This menu contains the basic tools of InfoSWMM SA that allow you to run the simulation and report the results. The basic modeling and analysis tools are incorporated into the Tools Menu.
The Connectivity submenu is used to verify network connectivity before running a simulation. When importing a model network from an external data source (GIS, infrastructure inventory, other hydraulic model, etc.), it is critical that the network representation be properly formed (each pipe is connected to exactly two nodes, each node is connected to at least one pipe). Otherwise, errors will be reported when attempting to run a simulation.
To verify network connectivity, go to the InfoSWMM SA Ribbon > InfoSWMM SA Tools and select Connectivity. There the user will see the following options:
The Locate/Fix submenu is used to verify network connectivity before running a simulation. When importing a model network from an external data source (GIS, infrastructure inventory, other hydraulic model, etc.), it is critical that the network representation be properly formed (each pipe is connected to exactly two nodes, each node is connected to at least one pipe). Otherwise, errors will be reported when attempting to run a simulation.
To verify network connectivity, go to the InfoSWMM SA Ribbon > InfoSWMM SA Tools and select Locate/Fix. There the user will see the following options:
The Utilities submenu is used to verify network connectivity before running a simulation. When importing a model network from an external data source (GIS, infrastructure inventory, other hydraulic model, etc.), it is critical that the network representation be properly formed (each pipe is connected to exactly two nodes, each node is connected to at least one pipe). Otherwise, errors will be reported when attempting to run a simulation.
To verify network connectivity, go to the InfoSWMM SA Ribbon > InfoSWMM SA Tools and select Utilities. There the user will see the following options:
When you define a scenario, you pick the facility, data, and option sets that comprise that scenario. When picking data sets for inclusion in a scenario, you may either specify that a data set associated with a given scenario is used independent of other scenarios, or alternatively may specify that the given data set inherits its contents – properties – from a “parent” scenario. Once you have configured and created a scenario, you can activate that scenario either by selecting the button from the Scenario Explorer tools or by using the Active Scenario Combo Box () from theInfoSWMM H2OMap SWMM InfoSWMM SA Control Center Toolbar Standard Toolbar at any time. Once a scenario is activated, any modifications made to any of the databases related to InfoSWMM H2OMap SWMM InfoSWMM SA facilities will be changed, but only for the data sets that are related to, and dependent upon, the active scenario.
Do the following to Create a Scenario:
Note:
The Dynamic Wave page of the Simulation Options dialog, shown below, 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.
Contents of this simulation option dialog page are described below:
Name  Description 
Inertial Terms  Indicates how the inertial terms in the St. Venant momentum equation will be handled.

Variable Time Step  Indicates whether or not a variable time step should be used. The variable step is computed for each time period so as to satisfy the Courant stability criterion for each conduit and to prevent an excessive change in water depth at each node. The Routing Time Step Summary Report is available for checking statistics about how InfoSWMM is altering the timestep.

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 fullflow 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 means that no conduits will be lengthened. The roughness value of the conduit will also be artificially lowered so that the same velocity and flow are maintained after lengthening. Also note that the conduit slope reported in the output will reflect a numerically smaller slope due to a longer conduit length.
Conduit Lengthening in InfoSWMM H2OMap SWMM InfoSWMM SA If you use the conduit lengthening option in InfoSWMM H2OMap SWMM InfoSWMM SA then your short conduits will be lengthened based on the CFL or explicit time step criterion. Any conduits in which the Length Factor or the courant time step link length over the original length is greater than 1 will be lengthened and will have its roughness lowered so that the conduit is hydraulically the same at full conduit depth. The full area, full width and full hydraulic radius stay the same in the modified link – only the length, slope and roughness are altered. 
Minimum 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 ft2 (i.e., the area of a 4ft diameter manhole) is used. 
Use Normal Flow Limit  Selects which condition is used to make InfoSWMM H2OMap SWMM InfoSWMM SA limit the flow in a conduit to the normal flow computed from the Manning equation:
The effect of these three options is on the value of sigma for the non linear term in the St Venant Equation; a sigma value of 1 means that the whole term is used, a value of 0 means that the non linear term is not used for that time step. 
Force Main Equation  Choose the head loss equation to be used to model force mains 
Maximum Number of Iterations  Allows you to control the maximum number of iterations in the solution. The number of iterations range from 2 to a possible 20 iterations. 
Stopping Tolerance  Controls the Stopping tolerance (internal units of feet) for node iterations. 
Two new parameters and a modified table in the output starting in InfoSWMM 11 and H2OMAP SWMM v10 that does the following:
1. Allows you to control the maximum number of iterations in the solution,
2. Controls the Stopping tolerance (internal units of feet) for node iterations, and
3. Shows not only the percent continuity error at a node but the error in million gallons (Mgal)
If you have a high continuity error or want to reduce your existing continuity error then you can increase the number of iterations or lower the stopping tolerance so that at each time step there is less continuity error.
The flow classification summary report is available only if the flow routing option used is dynamic wave. This report summarizes the flow regimes experienced by all or selected conduits in the system.
The following variables are displayed on the flow classification summary report for all or selected conduits depending on the report scope ( i.e., show complete report/graph, select elements, use Domain, use selection set, use provided element ID(s)) chosen on the Output Report and Graph dialog box. The summary is provided for the entire reporting length specified in the simulation options – dates tab.
Description of buttons and fields in the report.
BUTTON  NAME  DESCRIPTION 
Refresh Report  
Print Report  
Format Report  
Format Column  
Change Font  
Copy  
Sort Ascending  
Sort Descending  
Filtering  
Find  
Frequency Graph  Click here to learn more.  
Save Selection  
Compare Report  
Report Time Step  
ID  Conduit node identifier  
Adjusted/Actual Length  If the Conduit Lengthening option is used during a dynamic wave simulation, the ratio of adjusted to actual length is reported.  
Dry Flow Time  Total duration of time the entire conduit length was dry (i.e. conveyed zero flow)  
Upstream Dry Flow Time  Total duration of time the upstream end of the conduit remained dry  
Downstream Dry Flow Time  Total duration of time the downstream end of the conduit remained dry  
Subcritical Flow Time  Total duration of time the flow regime in the conduit was under subcritical condition  
Supercritical Flow Time  Total duration of time the flow regime in the conduit was under supercritical condition  
Upstream Critical Flow Time  Total duration of time the flow regime at the inlet end of the conduit remained under critical condition  
Downstream Critical Flow Time  Total duration of time the flow regime at the outlet end of the conduit remained under critical condition  
Average Froude Number  The average Froude Number, averaged across the simulation duration, maintained by the conduit  
Average Flow Change  Average change in flow experienced by the conduit 
SWMM5 water quality can simulate the generation, inflow and transport of any number of userdefined pollutants. Required information for each pollutant includes:
1  pollutant name 
2  concentration units (i.e., milligrams/liter, micrograms/liter, or counts/liter) 
3  concentration in rainfall 
4  concentration in groundwater 
5  concentration in inflow/infiltration 
6  concentration in dry weather flow 
7  initial concentration throughout the conveyance system 
8  firstorder decay coefficient. 
Copollutants can also be defined in SWMM5. For example, pollutant X can have a copollutant 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.
The Pollutant Editor is invoked whenever 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 for any specific node of the conveyance system by editing the node’s Inflows property.
Decay Coefficient
Firstorder 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).
CoPollutant
Name of another pollutant whose runoff concentration contributes to the runoff concentration of the current pollutant.
CoFraction
Fraction of the copollutant’s runoff concentration that contributes to the runoff concentration of the current pollutant.
An example of a copollutant 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 copollutant for the heavy metal.
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 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 proportional to time (t) raised to some power, until a maximum limit is achieved,
where C1 = maximum buildup possible (mass per unit of area or curb length), C2 = buildup rate constant, and C3 = time exponent.
Exponential Function
Buildup follows an exponential growth curve that approaches a maximum limit asymptotically,
where C1 = maximum buildup possible (mass per unit of area or curb length) and C2 = buildup rate constant (1/days).
Saturation Function
Buildup begins at a linear rate that continuously declines with time until a saturation value is reached,
where C1 = maximum buildup possible (mass per unit area or curb length) and C2 = halfsaturation 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 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 in units of mass per hour is proportional to the product of runoff raised to some power and to the amount of buildup remaining, i.e.,
where C1 = washoff coefficient, C2 = 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 per 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, i.e.,
where C1 = washoff coefficient, C2 = washoff exponent, and Q = runoff rate in userdefined flow units.
Event Mean Concentration
This is a special case of Rating Curve Washoff where the exponent is 1.0 and the coefficient C1 represents the washoff pollutant concentration in mass per liter. The conversion between userdefined 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.
The control of odorous gases and the corrosion of sewers are the two most important problems in operating wastewater collection systems. Evaluation of existing or potential odor or corrosion problems, and identification of where such problems will occur is, therefore, highly essential. In sanitary sewer systems, odors are produced as a result of biological decomposition of organic matter, particularly those containing sulfur and nitrogen, under anaerobic conditions prevailing in the slime layer of gravity pipes, force mains, and wet wells. Hydrogen sulfide and ammonia are the only malodorous inorganic gases produced from the decomposition. Other odor producing substances include organic vapors such as idoles, skatoles, mercaptans and nitrogenbearing organics. However, Hydrogen Sulfide (H2S) is the most commonly known and prevalent odorous gas associated with domestic wastewater collection and treatment systems. InfoSWMM H2OMap SWMM InfoSWMM SA gives wastewater engineers a powerful Operations and Maintenance ( O&M) tool to readily model and analyze entire sewer collection systems for sulfide generation and corrosion potential under varying conditions anticipated throughout the life of their systems.
Hydrogen sulfide has a characteristic rotten egg odor, is extremely toxic, is corrosive to metals, and is a precursor to the formation of sulfuric acid (which corrodes concrete, leadbased paints, metals, and other materials). The conditions leading to the formation of Hydrogen Sulfide generally favor the production of other odorous organic compounds. Therefore, investigation of the conditions favoring the Hydrogen Sulfide formation not only helps to quantify the potential for odor generation from other compounds, but also it aids in identifying potential corrosion problems in the collection system.
The occurrence of Hydrogen Sulfide in wastewater collection systems, other than that added from industrial sources and infiltrated groundwater, is primarily the result of the reduction of sulfate ion (), one of the most universal anions occurring in natural waters, under anaerobic conditions, as shown by the following reaction.