WWHM-SWMM Real Projects

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Real Projects

WWHM-SWMM In Action:

Yauger Park - Olympia Wa.

The City of Olympia contracted with Clear Creek Solutions to provide hydrologic and hydraulic modeling services to develop solutions to reduce flooding in the Yauger Park drainage system caused by large events like the December 2007 flood. WWHM-SWMM was used to model the complex hydrologic and hydraulic interactions.

Because the Yauger Park facility is a large regional facility back to back events impact the hydrology and because the outfall is a flat pipe system hydraulics are critical. The only way to truely model the system is to use both HSPF(WWHM) and SWMM. In this way it was possible to model the continous impacts to the facility and the outfall.

We ran mulitple future conditions scenarios in an effort to find the most efficient way to reduce the flooding in the intersection of Cooper Pt. Rd. and Black Lake Blvd. This project is still ongoing.

Client: City of Bothell, Washington

The City of Bothell contracted with Clear Creek Solutions, Inc., to investigate the observed street and private property drainage problems along 35th Avenue SE between 228th Street SE and 240th Street SE and south of 240th Street SE to Monte Villa Parkway.

35th Avenue SE floods due to high flows from Cole Woods Creek. The Cole Woods Creek culvert under 35th Avenue SE is undersized, as are the culverts on the east side of 35th Avenue SE/Cole Woods Creek stream crossing south to the intersection at 240th Street SE. Additional runoff from the hillside on the east side of 35th Avenue SE contribute to the street flooding along and down 35th Avenue SE to 242nd Street SE (Monte Villa Parkway) to a low spot east of 35th Avenue SE. The purpose of this study is to model existing flooding conditions and provide a solution to alleviate future flooding under full build-out conditions.

Clear Creek Solutions used WWHM-SWMM (HSPF hydrology linked to SWMM hydraulics) to model the 575-acre Monte Villa Parkway/ Cole Woods Creek drainage area and the multiple culverts along 35th Avenue SE between 228th Street SE and 240th Street SE.

The WWHM-SWMM modeling used long-term 15-minute precipitation to compute runoff and peak flows used in the flood frequency calculations. The January 7-8, 2004, rainfall event was found to be the best single storm event for use in the calculation of the 100-year flood flows. This is because it was a relatively high intensity rain event, thus making it an appropriate event for culvert sizing. This was confirmed by Log Pearson Type III flood frequency analysis of the annual peak flows for the period of 1948-2017.

Inside WWHM-SWMM the HSPF runoff was automatically converted into a binary EPA SWMM5 interface file that then connected all of the runoff basins to the appropriate nodes for input into the SWMM5 model. SWMM5 was then used to route the flood flows through the culverts and in the ditch on the east side of 35th Avenue SE to 240th Street SE. West of 35th Avenue SE there are two drainage systems, one is a low flow swale and the other is the high-flow bypass consisting of a series of culverts and vaults that carry flow to North Creek. Overflow to 242nd Street SE (Monte Villa Parkway) occurs when there are high flows in drainage system and backwater from North Creek.

Using WWHM-SWMM the 100-year flood event was routed through the upsized culverts. The Cole Woods Creek culvert was sized for fish passage and debris passage to comply with Washington State Department of Fish and Wildlife (WDFW) regulations. The other culverts along 35th Avenue SE were upsized, where needed, to convey the 100-year flood without overtopping and flooding 35th Avenue SE.

The project was completed on time and within budget using WWHM-SWMM’s HSPF continuous simulation hydrology and SWMM5’s dynamic wave hydraulics to accurately and efficiently model the study area.