1. Seattle’s Testing and Application of Low Impact Development BMPs in WWHM3 July 2006 Doug Beyerlein, P.E. Clear Creek Solutions, Inc.

2. Seattle’s Testing and Application of Low Impact Development BMPs in WWHM3 Presented at Stormcon 2006 in Denver, CO © 2006 Clear Creek Solutions, Inc. All rights reserved.

3. Clear Creek Solutions’ Stormwater LID Expertise Clear Creek Solutions, Inc., provides complete range of hydrologic and stormwater modeling services. Clear Creek specializes in continuous simulation hydrologic modeling. We have 30+ years of experience modeling complex hydrologic and stormwater problems. We created the Western Washington Hydrology Model Version 3 (WWHM3) for Washington State Department of Ecology. We teach WWHM and HSPF workshops.

4. Presentation Introduction Eco-Roof Modeling Bioretention Swale Modeling Questions & Answers

5. Introduction Seattle Public Utilities (SPU) is using new approaches to managing stormwater with the use of BMPs that mimic natural drainage systems. These BMPs are designed to: 1.Manage flooding in neighborhoods 2.Improve the appearance and function of the street right-of-way 3.Provide responsible stewardship of the environment 4.Help the City meet local, state, and federal environmental regulations

6. Introduction Seattle Public Utilities (SPU) has selected the following LID practices that can be used to return Seattle neighborhood creeks to more natural conditions: 1.Eco/green/vegetated roofs 2.Bioretention/landscape swales/rain gardens 3.Rainwater cisterns 4.Compost amended soils 5.Porous pavements

7. Examples of stormwater LIDs Green/vegetated/eco-roof

8. Examples of stormwater LIDs Green roofs

9. Examples of stormwater LIDs Rain garden/bioretention/landscape swale

10. Examples of stormwater LIDs Rain garden/bioretention/landscape swale

11. Examples of stormwater LIDs Rainwater cisterns

12. Examples of stormwater LIDs Compost amended soil

13. Examples of stormwater LIDs Permeable/porous pavement

14. Examples of stormwater LIDs Permeable/porous pavement

15. Introduction Seattle Public Utilities (SPU) uses monitoring and computer modeling to evaluate the effectiveness of different LID BMPs. LID computer modeling has been achieved by adding the LID practices to the Washington State Department of Ecology’s Western Washington Hydrology Model (WWHM), developed by Clear Creek Solutions, Inc.

16. Stormwater Modeling Traditional: Single event Today: Continuous simulation

17. Stormwater Modeling Single event modeling doesn’t work because:  Single-event flow frequency standards are based on inappropriate assumptions.  The need is to NOT increase flow durations for the range of erosive flows (for Western Washington the range is from 1/2 of the 2-year to 50-year flow event).

18. Stormwater Modeling Today: Continuous simulation Continuous simulation hydrology models the entire hydrologic cycle for multiple years.

19. Western Washington Hydrology Model (WWHM) Developed for the State of Washington Department of Ecology. Project Manager: Dr. Foroozan Labib Department of Ecology PO Box 47600 Olympia, WA 98504-7600 (360) 407-6439 email: flab461@ecy.wa.gov

20. Western Washington Hydrology Model (WWHM) Developed for the 19 counties of western Washington. Part of Ecology’s Stormwater Management Manual

21. WWHM Available free from the Washington State Department of Ecology web site: http://www.ecy.wa.gov/programs/wq/stormwater/

22. WWHM Flow duration standard: based on erosive flows. Erosive flow range: ½ of the 2-year to the 50-year

23. WWHM  Guidance/help is provided by  User Manual  Training Workshops  CCS Project Book

24. WWHM: LID Modeling WWHM3 includes the following LID options:  Green roof/eco-roof/vegetated roof  Bioretention/rain garden/landscape swale

25. Eco-Roof Modeling Study performed for Seattle Public Utilities Eco-roof modeled: Portland Hamilton Building Data provided by Portland BES

26. Eco-Roof Modeling Purpose: To determine appropriate HSPF hydrology parameter values to represent the eco-roof’s shallow soil depth and lack of a groundwater reservoir.

27. Eco-Roof Modeling Model Results: West Roof (2002-2005)

28. Eco-Roof Modeling Model Results: East Roof (2002-2005)

29. Eco-Roof Modeling Model Results: West Roof (January 2004)

30. Eco-Roof Modeling Model Results: East Roof (January 2004)

31. Eco-Roof Modeling Seattle Roof Flood Frequency Comparison Return Period (years)Reduction 224% 520% 1018% 2516% 5015% 10015%

32. Eco-Roof Modeling Seattle Roof Flow Duration Comparison Conventional Runoff Eco-Roof Runoff

33. Eco-Roof Modeling Seattle Roof Peak Runoff Comparison

34. Bioretention Modeling Model results: Seattle Swale N-2 (2004)

35. Bioretention Modeling Seattle Bioretention Frequency Comparison Return Period (years)Reduction 266% 563% 1064% 2566% 5067% 10069%

36. Bioretention/Rain Garden Modeling Stormwater volume reduction:

37. Summary Eco-roofs and bioretention swales reduce stormwater runoff and its associated problems. WWHM is a powerful stormwater modeling tool to help inform and persuade the public and policy makers of the benefits of using low impact development BMPs.

38. Acknowledgements Seattle Public Utilities provided information used in the modeling of eco- roofs and bioretention swales. The City of Portland, Oregon, Bureau of Environmental Services (BES) provided the Hamilton eco-roof monitoring data.

39. Questions? Contact: Doug Beyerlein 425.892.6454 beyerlein@clearcreeksolutions.com or Joe Brascher 360.943.0304 brascher@clearcreeksolutions.com beyerlein@clearcreeksolutions.com brascher@clearcreeksolutions.com