Sediment Erosion Control and Restoration Measures for the Spokane River, Washington

The Spokane River is a steep-gradient river that flows through the City of Spokane in eastern Washington. Large-sized sediments are eroded and transported down the river, with significant quantities deposited upstream of Avista Corporation's Monroe Street Hydroelectric Dam intake in the downtown area of Spokane. The impacts are river degradation, erosive damage to equipment, and disturbance of normal intake operations. Consequently, work crews must remove the sediment, which has typically been accomplished with disruptive and costly dredging operations. The major thrust of this study is the proposition of a new strategic plan for river restoration not based solely on qualitative assessment, but developed using quantitative analysis. This research utilizes two-dimensional hydrodynamic modeling, FESWMS, to map the flow patterns in the river. The results are used to identify and isolate areas of accelerated sediment erosion, and to develop river restoration methods to control upstream erosion.