New Restoration Approach for Steep-Gradient Streams: Spokane River Case Study

Steep-gradient streams present numerous challenges with respect to restoration techniques and numerical modeling. A new methodology is proposed for use as an approach to river restoration in hydraulically steep rivers. This approach utilizes the most current technology used in numerical modeling of river ecosystems to provide a quantitative as well as qualitative analysis of river flow, sediment transport, and geomorphology. The approach is applied to a case study on the Spokane River, a steep-gradient, bedrock-controlled river that flows through the City of Spokane in eastern Washington. This research utilizes two-dimensional modeling using the Finite Element Surface Water Modeling System computer program to develop a strategic plan for river restoration on the Spokane River. The research work that is the focus of this paper is the hydrodynamic component of the project. Hydrodynamic model results are used to identify and isolate areas of accelerated sediment erosion. Abbreviated research results (qualitative and quantitative) are presented for the two-year storm event flow in the Spokane River.