How to Model Ponds With SWMM5
The United States Environmental Protection Agency (EPA) has developed a storm water management model called SWMM 5. The model is publicly available free of charge and runs on computers with Windows operating systems. SWMM 5 allows engineers and hydrologists to estimate how much water may run off from urban areas due to rain storms. Model results are typically used to properly size ponds to collect storm water runoff, and their associated facilities, such as pumps and pipes.
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Instructions
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Create a new SWMM project by running the EPA SWMM program on a Windows-based computer and selecting "New" from the "File" menu on the main menu bar.
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Specify default values for hydrologic properties and parameters of the study area. Parameters include rainfall data where the pond is proposed to be constructed and the watershed area draining into the pond.
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Select the "Options" category from the data browser and it will show a "Simulation Options" dialog box with four categories of options: Process Models, Infiltration Model, Miscellaneous and Routing Model. To size a storm water pond, select "Rainfall/Runoff" and "Flow Routing" from the Process Models option. Select "Green Ampt" from the "Infiltration Model" option. Select "Kinematic Wave" as the "Routing Model" and leave the "Miscellaneous" options unchecked.
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Run a simulation by selecting "Run Simulation" from the "Project" menu, or click the lightning bolt icon.
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View the results of the model simulation by selecting "Status" from the "Reports" menu. The status report will show how much rain is anticipated to fall on the proposed pond site, how much water absorbed into the ground and how much water became runoff.
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Interpret the results of the model simulation. Size the proposed pond based on the amount of runoff from the model. After attempting a basic model run with SWMM 5, it may be necessary to hire an engineering consulting firm to conduct more detailed model runs.
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Tips & Warnings
As with any model, verify that results make physical sense.
If the model does not run, a status report will indicate what errors have occurred.
Before sizing a storm water pond based on model results, consult a registered civil or environmental engineer to evaluate what safety factors should be considered.
EPA provides a manual documenting how to use the SWMM 5 model, but does not provide ongoing technical support for its use.
References
Resources
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