EPA SWMM Notes and Tips

These notes and tips on modeling with EPA SWMM are mostly for me.

1. Very early on, set up ID prefixes under Project, Defaults and save as defaults for all new projects.
2. Choose Dynamic Wave routing (full St. Venant equations instead of Kinematic Wave) method under Project, Defaults, Nodes/Links.
3. Turn on Auto-Length at the bottom of the screen. SWMM does automatic pipe lengths, but not automatic sub-basin (catchment/watershed) areas.
4. Turn on ID displays under Tools, Map Options, Annotation.
5. Subcatchment areas are not automatic. Enter the area in acres.
6. Rainfall intensity time series are in inches per hour held constant for the time interval specified for the rain gage that uses the time series. So if you want a 5-minute intensity at the peak of the storm, you must include an intensity for all 5-minute intervals in the simulation time period.
7. If you calculate a rainfall time series (In this format: 01/01/2001 0:00 0.01) with a spreadsheet, you can save it to a tab-delimited file and read directly from the file in SWMM.
8. Use a Storage Unit node for all manholes and inlets to specify their internal and surface storage. Start by creating a "STD-MH" that works roughly for the general case. Eventually you probably want a custom storage description for every inlet. Make the Max. Depth higher than the expected ponding. If HGL exceeds the storage curve, it will extend as a cylinder up to the Max. Depth, at which point it will be lost (possible continuity violation). So make Max. Depth plenty high.