1. Introduction to the USEPA’s Storm Water Management Model (SWMM 5.0) David Rosenberg CEE 5460 – Water Resources Engineering

2. Learning Objectives Describe model components and inputs Enter rainfall, catchment, and other input data Generate the outflow hydrograph for a design storm over a catchment 2CEE 5460 http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/

3. What Is SWMM? Distributed, dynamic rainfall-runoff simulation model Simulate single or long-term (continuous) events 3 Runoff quantity and quality from primarily urban areas

4. What Is SWMM? Distributed, dynamic rainfall-runoff simulation model Simulate single or long-term (continuous) events 4 Runoff quantity and quality from primarily urban areas

5. Typical Uses Design and size drainage system components including detention facilities Map flood plains of natural channel systems Control combined and sanitary sewer overflows Generate non-point source pollutant loadings for wasteload allocation studies Evaluate BMPs and LIDs for sustainability goals CEE 5460David Rosenberg 5

6. Processes Simulated (grey = focus for CEE 5460) CEE 5460David Rosenberg 6

7. Visual Rain gage Subcatchment Junction Outfall Divide Storage unit Conduit Pump Orafice Weir Outlet Model Components CEE 5460David Rosenberg 7 Non-Visual Climate data LID controls Snow packs Aquifers Unit hydrographs Transects External inflows Control rules Pollutants Land uses Treatment Time-series

8. Representing land use in a subcatchment CEE 5460David Rosenberg 8 Outlet Pervious area Impervious area with depression storage Impervious area with no storage

9. Working with SWMM Backdrop image ToolsFile menu Object toolbar Edit objects Visual objects

10. Using SWMM CEE 5460David Rosenberg 10 StepLocation 1.Start a new projectFile menu 2.Set project defaultsProject=>defaults… 3.Set display settingsTools=>Map display settings… 4.Add visual objects to the mapObject toolbar 5.Enter data for visual objectsSeveral ways 6.Set up simulationData tree=>Options 7.Run simulationProject=>Run sim. 8.View resultsTool icons 9.Modify assumptionsSeveral ways

11. 2. Set project defaults Select Infiltration model David Rosenberg 11

12. Click an object from the object tool bar Place it on the map 4. Add visual objects SubcatchmentRain gage Junction Conduit Outflow For conduits, click the start object, then the destination object

13. 5. Enter data Right-click an object => select properties For subcatchments –Assign a rain gage –Assign an outlet –Enter data fields –Explanations are at the bottom! –Enter the Curve Number (for SCS method) by double- clicking Infiltration David Rosenberg 13

14. 5. Enter data (continued) Precipitation Add a rain gage Define the time- series David Rosenberg 14

15. 6. Simulation Set up Select Options=>General Select Process Models, Infiltration method, and Routing Model (steady flow for PBL-2) Set Dates of simulation period Set computational time step David Rosenberg 15

16. 7. Run the Simulation Select Project => Run Simulation Or click David Rosenberg 16

17. 7. Run the Simulation (cont.) Successful when continuity error is low (< 10%) David Rosenberg 17

18. 8. View Results Graphs Tables Statistics etc.

19. 8. View Results (cont.) David Rosenberg 19 CEE 5460

20. Example 1. Generate the runoff hydrograph from Lundstrum Park, Logan Use last Thursday’s 6-hr duration Layton storm with a 10-year recurrence interval Lunstrum Park (blue) 18.4 acres 1,440 ft length to divide Dense grass 40’ road width Location Elevation (ft.) East (canal)4,855 West (1600 E)4,810

21. Example 1. Questions to Answer 1.What inputs did you change/enter? 2.What is the peak flow? 3.When does the peak flow occur? 4.Why do these values differ from our example from Tuesday? Hint 1: What processes does SWMM simulate? SCS? Hint 2: Look at the precipitation intensity values David Rosenberg 21 CEE 5460

22. Example 1. Answers 1.Set the rain gage and outlet 2.Area = 18.4 ac 3.Width = Area/length to divide 4.% slope = 3.125% 5.%Imperv = 3% 6.N-imperv = 0.011 (from manual) 7.N-perv = 0.15 (from manual) 8.Dstore-imperv = 0.075 (manual) 9.Dstore-Perv = 0.15 (from manual) 10.Curve Number = 61 (from Sept 27)

23. Example 1. Answers (cont) 10.Set simulation time step 11.Resulting subcatchment runoff hydrograph David Rosenberg 23

24. Model Limitations Only for small-scale, urban watersheds Not applicable to forested areas or irrigated cropland Cannot be used with highly disaggregated (e.g., daily) rainfall data It’s an analysis tool, not an automated design tool David Rosenberg 24 CEE 5460

25. Conclusions SWMM simulates runoff from urban watersheds Includes precipitation, pervious and impervious land cover, depression storage, infiltration, etc. Can include pipes, channels, weirs, orafices, drainage systems, curbs, constructed features, and Detention basins (next week) CEE 5460David Rosenberg 25

26. Additional Resources Model downloads and documentation http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/ SWMM User’s Manual Yes, read it! Appendices provide suggested model inputs SWMM-USERS List Server Email: listserv@listserv.uoguelph.calistserv@listserv.uoguelph.ca With the statement in the body SUBSCRIBE SWMM-USERS [first name] [last name] CEE 5460David Rosenberg 26