seattle’s testing and application of low impact development bmps in wwhm3 july 2006 doug...
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Seattle’s Testing and Seattle’s Testing and Application of Low Application of Low
Impact Development Impact Development BMPs in WWHM3BMPs in WWHM3
July 2006July 2006
Doug Beyerlein, P.E. Doug Beyerlein, P.E.
Clear Creek Solutions, Inc.Clear Creek Solutions, Inc.
Seattle’s Testing and Seattle’s Testing and Application of Low Application of Low
Impact Development Impact Development BMPs in WWHM3BMPs in WWHM3
Presented at Stormcon 2006 in Presented at Stormcon 2006 in Denver, CODenver, CO
© 2006 Clear Creek Solutions, Inc.All rights reserved.
Clear Creek Solutions’ Clear Creek Solutions’ Stormwater LID ExpertiseStormwater 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.
PresentationPresentation
IntroductionIntroduction
Eco-Roof ModelingEco-Roof Modeling
Bioretention Swale ModelingBioretention Swale Modeling
Questions & AnswersQuestions & Answers
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 neighborhoods2. Improve the appearance and function
of the street right-of-way3. Provide responsible stewardship of the
environment4. Help the City meet local, state, and
federal environmental regulations
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 roofs2. Bioretention/landscape swales/rain
gardens3. Rainwater cisterns4. Compost amended soils5. Porous pavements
Examples of stormwater LIDsGreen/vegetated/eco-roof
Examples of stormwater LIDsGreen roofs
Examples of stormwater LIDsRain garden/bioretention/landscape swale
Examples of stormwater LIDsRain garden/bioretention/landscape swale
Examples of stormwater LIDsRainwater cisterns
Examples of stormwater LIDsCompost amended soil
Examples of stormwater LIDsPermeable/porous pavement
Examples of stormwater LIDsPermeable/porous pavement
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.
Stormwater Modeling
Traditional: Single event
Today: Continuous simulation
Stormwater ModelingStormwater 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).
Stormwater Modeling
Today: Continuous simulation
Continuous simulation hydrology models the entire hydrologic cycle for multiple years.
Western Washington Hydrology Model (WWHM)
Developed for the State of Washington Department of Ecology.
Project Manager: Dr. Foroozan LabibDepartment of EcologyPO Box 47600Olympia, WA 98504-7600(360) 407-6439email: [email protected]
Western Washington Hydrology Model (WWHM)
Developed for the 19 counties of western Washington.
Part of Ecology’sStormwater ManagementManual
WWHM
Available free from the Washington State Department of Ecology web site:
http://www.ecy.wa.gov/programs/wq/stormwater/
WWHM
Flow duration standard: based on erosive flows.
Erosive flow range: ½ of the 2-year to the 50-year
WWHM
Guidance/help is provided by User Manual Training Workshops CCS Project Book
WWHM: LID Modeling
WWHM3 includes the following LID options:
Green roof/eco-roof/vegetated roof
Bioretention/rain garden/landscape swale
Eco-Roof ModelingStudy performed for Seattle Public Utilities
Eco-roof modeled: Portland Hamilton Building
Data provided by Portland BES
Eco-Roof ModelingPurpose: To determine appropriate HSPF hydrology parameter values to represent the eco-roof’s shallow soil depth and lack of a groundwater reservoir.
Eco-Roof ModelingModel Results: West Roof (2002-2005)
Eco-Roof ModelingModel Results: East Roof (2002-2005)
Eco-Roof ModelingModel Results: West Roof (January 2004)
Eco-Roof ModelingModel Results: East Roof (January 2004)
Eco-Roof ModelingSeattle Roof Flood Frequency Comparison
Return Period (years) Reduction
2 24%
5 20%
10 18%
25 16%
50 15%
100 15%
Eco-Roof ModelingSeattle Roof Flow Duration Comparison
Conventional RunoffEco-Roof Runoff
Eco-Roof ModelingSeattle Roof Peak Runoff Comparison
Bioretention ModelingModel results: Seattle Swale N-2 (2004)
Bioretention ModelingSeattle Bioretention Frequency Comparison
Return Period (years) Reduction
2 66%
5 63%
10 64%
25 66%
50 67%
100 69%
Bioretention/Rain Garden ModelingStormwater volume reduction:
Stormwater Reduction (%) for Seattle Soils
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Ratio of Rain Garden Area to Impervious Area
Red
uct
ion
Till Outwash
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.
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.
Questions?Contact:
Doug Beyerlein425.892.6454
or Joe Brascher360.943.0304