Drainage Analysis & Flood Mitigation

Client—City of Oakville, Washington

The City hired Gibbs & Olson to perform a drainage analysis to identify and evaluate three alternatives for flood mitigation and provide opinions of total project cost. The analysis included recommending an alternative for implementation. The final drainage analysis and the recommended alternatives were presented in a stormwater report.

Field reconnaissance was performed to evaluate the existing drainage patterns upstream and downstream of Highway 12 as well as to verify drainage structures listed on the map provided by the City. The final report included a basin delineation of the area draining to a 36 inch culvert under Highway 12,  a basin hydraulic model, recommending alternatives for improvements and providing associated opinions of probable construction cost. We also performed a topographic survey of the existing culverts and larger ditch cross-sections for the hydraulic modeling.