Sediment Impact Assessment of Columbia River System Operations

A 2020 Environmental Impact Statement (EIS) was completed to review and update management of the Columbia River System (CRS) comprised of fourteen federal water regulation projects in Idaho, Montana, Oregon, and Washington. The CRS includes both storage and run-of-river regulation projects in four major subbasins. In support of the EIS alternatives analysis, a suite of river mechanics metrics were developed to assess potential response within the CRS. Spatiotemporal distributions of hydraulics and sediment metrics were computed using daily timeseries representing a standardized suite of 5000-year stochastic hydroperiods to quantify baseline conditions and assess potential change within 82 sub-reaches under multiple EIS alternatives. This presentation summarizes two sediment impact metrics of interest in the run-of-river reaches: the potential for changes in sediment passing reservoirs and reaches, and the potential for changes in bed material.