In the Savannah River, USACE is reconnecting seven historic meanders that were removed for navigation and sediment transport improvement. The project requires the installation of new hydraulic controls to rout the river back into its historic channel. We evaluated the impacts of re-meandering one section of the Savannah River with 2 alternatives on Atlantic Sturgeon. An existing 1D HEC-RAS model was repurposed as a 2D model representing current and planned future conditions. One of the primary uncertainties of the project is the impact of the hydraulic controls on migratory fishes including Atlantic and Shortnose Sturgeon. We compared velocities, depths, and water surface slopes across scenarios. We modeled the swimming behavior of various-sized sturgeon using a particle-based fish movement model and computed ground speed, swim speed and spatial distribution of fish as proxies for ecological benefit across scenarios. Swim behavior suggests that the increased channel length associated with the meander bend reduced swimming exertion and increased ground speed while spatial distribution was sensitive to the volume of water in the channel. The work suggests that ecological benefits associated with fish migration are readily computed using 2D models early in the planning and feasibility phase of projects and that cost-benefit estimates are readily calculated. Using 2D models with fish biomechanical data reduces reliance on qualitative assessments of impacts and improves the USACE ability to design ecological restoration projects.
