seattle’s testing and application of low impact development bmps in wwhm3 july 2006 doug...

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: flab461@ecy.wa.gov

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

beyerlein@clearcreeksolutions.com

or Joe Brascher360.943.0304

brascher@clearcreeksolutions.com