Using Two Dimensional Hydraulic Models for Restoration of Upper Columbia Basin Streams

The use of two-dimensional hydraulic models for assistance in understanding of Upper Columbia Basin Streams was applied on the Upper Methow River located in Washington State. The Upper Columbia Spring Chinook Salmon, Steelhead and Bull Trout Recovery Plan (UCSRB, 2007) identified potential restoration strategies for basins in the upper Columbia. The UCSRB recovery plan recommended additional research to identify locations for preservation and restoration and also recommended additional examination of fluvial geomorphic processes to assess how processes affect habitat creation and loss. Identifying fluvial processes for existing and future conditions was applied to understand channel complexity for side channel and floodplain connectivity and for in-channel habitat. The SRH-2D (Sediment and River Hydraulics Two-dimensional) model was applied to a reach in the Upper Methow to determine existing and future channel processes. Application of the model enhanced understanding of channel processes and floodplain and side channel connectivity to help identify potential restoration and preservation projects. The model was able to provide quantitative results for bankfull and higher flows that provide indicators of channel and floodplain function, particularly when combined with geomorphic mapping and biological analysis from a multi-disciplined technical team.