Western Washington Western Washington Hydrology ModelHydrology Model

Version 3Version 3

Vancouver, WA, Workshop

October 17, 2007 AMOctober 17, 2007 AM

Western Washington Western Washington Hydrology ModelHydrology Model

Version 3Version 3

Instructors: Instructors: Doug Beyerlein, P.E. Doug Beyerlein, P.E.

Joe BrascherJoe Brascher

Clear Creek Solutions, Inc.Clear Creek Solutions, Inc.www.clearcreeksolutions.comwww.clearcreeksolutions.com

Clear Creek Solutions’ Clear Creek Solutions’ Hydrology ExpertiseHydrology 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 WWHM3 for Washington State Department of Ecology and are adapting it to model San Francisco Bay Area watersheds and facilities.

• We teach WWHM and HSPF workshops.

WWHM Introduction

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

WWHM Introduction

Developed for the 19 counties of western Washington.

Part of Ecology’sStormwater ManagementManual

WWHM Introduction

WWHM3 Standard is available free from the Washington State Department of Ecology web site:

http://www.ecy.wa.gov/programs/wq/stormwater/

WWHM Background and Theory

Ecology’s Stormwater Management Manual

Specifies a flow duration standard

Requires the use of Western Washington Hydrology Model (WWHM) or equivalent

WWHM Background and Theory

Flow duration standard: based on erosive flows.

Erosive flow range: ½ of 2-year to 50-year flow.

WWHM Background and Theory

Flow Duration Analysis: Percent of time the flow exceeds a specific value.

Requires continuous simulation hydrology to compute flow duration.

WWHM Background and Theory

Continuous simulation hydrology models the entire hydrologic cycle for multiple years.

Stormwater runoff = surface runoff + interflow.

WWHM Capabilities

WWHM uses continuous simulation hydrology to compute stormwater runoff for both

predevelopment and post-development conditions.

Predevelopment Post-development

WWHM Capabilities

WWHM continuous simulation computations from HSPF (included in WWHM software).

HSPF runs in the background with calibrated parameter values and local meteorological data.

HSPF sponsored and funded by EPA and USGS.

How WWHM/HSPF works

Drainage areas are divided into pervious land segments based on soil, vegetation, and land slope and impervious land segments.

Pervious and impervious segments are linked to conveyance pathways (pipes, ditches, ponds, streams, rivers, lakes, etc.)

Historic rainfall and evaporation are used as input.

How WWHM/HSPF works

The entire water cycle is modeled on an hourly or shorter time step for multiple years.

The model computes changes in soil moisture, evapotranspiration, and runoff every time step.

Three types of runoff: surface runoff interflow groundwater/base flow

How WWHM works

Calibrated parameter values are built into WWHM (different calibrated parameter values are used for different climatic regions).

Local precipitation and evaporation data are included in WWHM.

How WWHM works

User locates project on county map, inputs pre- and post-development land use, and proposed mitigation measure(s).

Predevelopment and mitigated flows are compared at Point of Compliance (POC).

Mitigated flows are not allowed to exceed flow duration standards.

How WWHM works

User outputs report file and project file.

Output files can be submitted to the permitting agency for approval.

Permitting agency can load project file and rerun analysis, if needed.

Report file summarizes input data and output results.

How WWHM works

Guidance/help is provided by User Manual Training Workshops CCS Project Book* Tech Support*

* Go to www.clearcreeksolutions.com for more details.

WWHM Version 3:

Goal: give the user greater flexibility and options:

High groundwater element Lateral flow between basins More elements More output options New LID options

WWHM Version 3:

Version 3 projects have no drainage area size limitations: entire watersheds can be modeled.

Version 3 can be customized to local jurisdictions (e.g., City of Bellingham, City of Seattle).

WWHM3 Standard:14 elements:

1. basin2. trapezoidal pond3. tank4. lateral pervious basin (NEW)5. high groundwater/wetland (NEW)6. vault7. open channel (NEW)8. time series (NEW)9. lateral impervious basin (NEW)10. gravel trench bed (NEW)11. sand filter12. flow splitter (IMPROVED)13. irregular-shaped pond14. stage-storage-discharge table

WWHM3 PRO Basic:

WWHM3 Standard plus: user selected time step (5 minutes to one hour) tagged flow routing additional elements

culverts green/vegetated/eco-roofs bioretention swales/rain gardens

WWHM3 PRO GIS:

WWHM3 PRO Basic plus: Map Explorer

WWHM3 PRO GIS:

WWHM3 PRO Basic plus: GIS Import

GIS Import Process Diagram1

2

3

4

5

WWHM3 PRO SWMM:

WWHM3 PRO Basic plus: SWMM Routing

WWHM3 PRO Complete:

WWHM3 PRO Basic plus: SWMM GIS

WWHM3 LID Modeling

Green/vegetated/eco-roof Bioretention swales/rain gardens Porous pavement

WWHM3 LID Modeling

Green/vegetated/eco-roof

WWHM Green Roof ModelingStudy performed for Seattle Public Utilities

Green roof modeled: Portland Hamilton Building

Data provided by Portland BES

WWHM Rain Garden ModelingSeattle Bioretention Swales

WWHM Rain Garden Modeling

Native Soil

Native Soil

Native Soil

Amended Soil (1-3 layers)

Weir and vertical orifice outlet

Underdrain (optional)

WWHM Porous Pavement Modeling

Currently represented by the gravel trench bed element.