Integrating Simulation and Design for Stormwater Management

1. Integrating Simulation and Designfor Stormwater Management by Alan A. Smith Alan A. Smith Inc. Dundas, Ontario, Canada

2. A SWMM Program Classification Scheme

3. Representing a Drainage Network as a Tree 11 Nodes 10 Links

4. A node numbering convention

5. A time-wise marching solution Intermediateinflow DQ(j) DownstreamboundaryH = f(Q,t) UpstreamboundaryQ = Q(t)

6. A downstream marching solution Intermediateinflow DQ(j) UpstreamboundaryQ = Q(t)

7. Hydrology options in MIDUSS 98

8. Design options in MIDUSS 98 • Pipes - part-full uniform flow • - surcharged HGL • Channels - simple trapezoidal • - complex (50 points) • Pond - detention, rooftop, parking lot, super-pipe • Exfiltration trench - split inflow between outflow and exfiltration • Diversion - split major and minor flows • Route - modified Muskingum-Cunge method

9. Benefits of On-Site Detention(for commercial developments) (1) Should be explored before end-of-pipe BMP (2) Runoff should be attenuated locally when possible (3) Local control of peak flow reduces hydraulic load on centralized quality control (4) Peak flow reduction reduces re-suspension of settled solids (5) Reduce cost of centralized SWM facility (6) Facilitates cost-sharing between benefiting parties.

10. Idealized discretization ofa commercial development

11. Rooftop storage • Define catchment 100% impervious • For 450 sq.m./RD set L = 10 m @ 0.5% • Generate runoff hydrograph • Add to Inflow hydrograph • Design pond - use Rooftop option • Confirm/edit parameters 24 litres/min/25mm • Route hydrograph

12. Rooftop storage - Q,V = f(H) Volume Discharge

13. Rooftop storage - Results

14. Parking lot storage (1)

15. Parking lot storage (2) Volume Rim elevation Discharge Catch basin Invert level Rim capacity

16. Parking lot storage (3) Rim Elevation

17. Flood routing Time T Nucleus Ti+1 Dt Cr=cDt/Dx=2 bDt Unstable Ti aDx Dx Distance X Xj Xj+1

18. Muskingum-Cunge method Diffusion equation is where D can be defined by: subject to stability criteria

19. Running in Automatic mode Created in previous manual run

20. Running in Automatic mode • Test previous design for more severe storm • Complete design in 2 or more sessions • Add extra commands • Modify design for more severe storm

21. Edit Paneland Control Panel

22. Applications of MIDUSS 98 • Program functionality has been developed over many years of professional practice. • Has proved valuable in ‘fleshing out’ Master Drainage Plans to separate local and centralized SWM facilities • Most recent application in Belleville, Ontario to 400 ha catchment to assign cost sharing among two municipalities, 8 to 10 new developments and many existing developments.

23. Conclusions • Drainage design cannot easily separate simulation and design

24. Conclusions • Drainage design cannot easily separate simulation and design • Design process needs a highly interactive decision support system

25. Conclusions • Drainage design cannot easily separate simulation and design • Design process needs a highly interactive decision support system • Automatic mode allows sensitivity of design to storm magnitude to be tested incrementally.

26. Conclusions • Drainage design cannot easily separate simulation and design • Design process needs a highly interactive decision support system • Automatic mode allows sensitivity of design to storm magnitude to tested be incrementally. • Versatile hydrology simulation and flexible, interactive design provides a training tool for professional and student.