1. Western Washington Hydrology Model Version 3
Vancouver, WA, Workshop
October 17, 2007 AM

2. Western Washington Hydrology Model Version 3
Instructors:
Doug Beyerlein, P.E.
Joe Brascher
Clear Creek Solutions, Inc.

3. Clear Creek Solutions’ Hydrology 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.

4. WWHM Introduction
Developed for the State of Washington Department of Ecology.
Project Manager: Dr. Foroozan Labib
Department of Ecology
PO Box 47600
Olympia, WA
(360)

5. WWHM Introduction Developed for the 19 counties of western Washington.
Part of
Ecology’s
Stormwater
Management
Manual

6. WWHM Introduction
WWHM3 Standard is available free from the Washington State Department of Ecology web site:

7. 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

8. WWHM Background and Theory
Flow duration standard: based on erosive flows.
Erosive flow range: ½ of 2-year to 50-year flow.

9. WWHM Background and Theory Flow Duration Analysis: Percent of time the flow exceeds a specific value.
Requires continuous simulation hydrology to compute flow duration.

10. WWHM Background and Theory
Continuous simulation hydrology models the entire hydrologic cycle for multiple years.
Stormwater runoff = surface runoff + interflow.

11. WWHM Capabilities Predevelopment Post-development
WWHM uses continuous simulation hydrology to compute stormwater runoff for both predevelopment and post-development conditions.
Predevelopment Post-development

12. 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.

13. 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.

14. 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

15. 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.

16. 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.

17. 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.

18. How WWHM works Guidance/help is provided by User Manual
Training Workshops
CCS Project Book*
Tech Support*
* Go to for more details.

19. 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

20. 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).

21. WWHM3 Standard: 14 elements: basin trapezoidal pond tank
lateral pervious basin (NEW)
high groundwater/wetland (NEW)
vault
open channel (NEW)
time series (NEW)
lateral impervious basin (NEW)
gravel trench bed (NEW)
sand filter
flow splitter (IMPROVED)
irregular-shaped pond
stage-storage-discharge table

22. 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

23. WWHM3 PRO GIS:
WWHM3 PRO Basic plus:
Map Explorer

24. GIS Import Process Diagram
WWHM3 PRO GIS:
WWHM3 PRO Basic plus:
GIS Import
GIS Import Process Diagram 1 2 3 4 5

25. WWHM3 PRO SWMM:
WWHM3 PRO Basic plus:
SWMM Routing

26. WWHM3 PRO Complete:
WWHM3 PRO Basic plus:
SWMM
GIS

27. WWHM3 LID Modeling Green/vegetated/eco-roof
Bioretention swales/rain gardens
Porous pavement

28. WWHM3 LID Modeling
Green/vegetated/eco-roof

29. WWHM Green Roof Modeling
Study performed for Seattle Public Utilities
Green roof modeled: Portland Hamilton Building
Data provided by Portland BES

30. WWHM Rain Garden Modeling
Seattle Bioretention Swales

31. WWHM Rain Garden Modeling
Weir and vertical orifice outlet
Amended Soil (1-3 layers)
Native Soil
Native Soil
Underdrain (optional)
Native Soil

32. WWHM Porous Pavement Modeling
Currently represented by the gravel trench bed element.