Land Development Stormwater Analysis

A private client contracted with Clear Creek Solutions to investigate potential downstream flooding in conjunction with a proposed land development in Western Washington. The development will be constructed to provide direct discharge from the project site through a tide gate to Puget Sound.

Process and Solution

Clear Creek Solutions used WWHM-SWMM (HSPF hydrology linked to SWMM hydraulics) to model the development and adjacent drainage areas and the city storm drainage pipe system down to the tide gate and Puget Sound.

Tidal influences were included in the SWMM hydraulics.

Clear Creek Solutions ran the WWHM-SWMM model for the period of October 1948 to September of 2009.

A stage frequency analysis was then performed on the annual maximum stage values.

WWHM-SWMM simulated stage data were searched for events that produced stages that were equal or nearly equal to the values in the stage frequency analysis.

Six events were then selected for further analysis.

Peak stages for all six events for both the existing and developed conditions were computed in 12 different model runs using WWHM-SWMM’s TurboSWMM feature.

Using TurboSWMM the long SWMM5 runs that would normally take days to complete were run in only a few hours using multiple computer co-processors.

Results

Modeling results show water depth upstream of the tide gate increases only 0.26 feet for the 2-year flood and 0.13 feet for the 100-year flood.

The reason why the 2-year flood elevation increase is greater than the 100-year is because the area behind the tide gate available for inundation for the lower water depth is less than for the higher depths.

So it takes less of an increase in volume to increase the water depth for the smaller flood events.

The WWHM-SWMM stormwater analysis showed that the proposed land development will not adversely impact downstream property owners.

There will be only a slight increase in the maximum water surface elevations behind the tide gate.

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.

Our Projects

Land Development Stormwater Analysis
Land Development Stormwater Analysis

A private client contracted with Clear Creek Solutions to investigate potential downstream flooding in conjunction with a proposed land development in Western Washington. The development will be constructed to provide direct discharge from the project site through a tide gate to Puget Sound.

Government Canal Stormwater Analysis Study
Government Canal Stormwater Analysis Study

The City of Pacific contracted Clear Creek Solutions as the stormwater modeling subconsultant to find a pump solution to alleviate flooding in and around the Government Canal.

Monte Villa Parkway Drainage Study
Monte Villa Parkway Drainage Study

The City of Bothell contracted Clear Creek Solutions 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.

Yauger Park Regional Stormwater Facility Expansion
Yauger Park Regional Stormwater Facility Expansion

Clear Creek Solutions (CCS) and Davido Consulting Group (DCG) were selected by the City of Olympia to assist in the proposed expansion of a joint-use recreation and stormwater flow control facility.

Hydrologic And Hydraulic Modeling Of The Yauger Park Drainage Basin
Hydrologic And Hydraulic Modeling Of The Yauger Park Drainage Basin

The City of Olympia contracted with Clear Creek Solutions to provide hydrologic and hydraulic modeling services. Our solutions were successful in reducing flooding in the Yauger Park drainage system caused by large events like the December 2007 flood.

Edwards Aquifer Recharge Modeling
Edwards Aquifer Recharge Modeling

Comparative analyses were made to determine the preferred precipitation data set for the model.

Costco Stormwater Facility Sizing
Costco Stormwater Facility Sizing

Costco's development of a new store in south Snohomish County, just north of Woodinville, required innovative strategies and analysis to protect adjacent Little Bear Creek.

HSPF Watershed Calibration Clark County, WA
HSPF Watershed Calibration Clark County, WA

Clark County contracted with Otak to update the County's stormwater ordinance. Clear Creek Solutions was hired to produce HSPF calibrations of two watersheds in the county.

Olympia Sea Level Rise Modeling
Olympia Sea Level Rise Modeling

Clear Creek Solutions constructed a WWHM-SWMM model of the City of Olympia drainage systems impacted by a rise in sea levels and associated Puget Sound high tides.

TOP