Low head dams are common throughout the U.S. They are typically used as diversion structures to manage river flows for agricultural or recreational use. They tend to have a relatively low elevation change and nearly full length, curved crests. Due to the relatively low change in water surface elevation these dams often appear safe or traversable even under flood conditions. However, these structures can develop a highly aerated recirculating rolling flow pattern just downstream of the crest which can be fatal to recreational users. CFD modeling was used to evaluate a series of proposed upgrades to the dam to reduce the potential for this characteristic recirculating roller flow and improve safety. These upgrades included various stepped spillway arrangements which were evaluated over a range of flows. A final model was developed including the river bathymetry upstream and downstream of the dam to evaluate key flows with the recommended upgraded configuration. The modeling was used to effectively identify key changes and guide the design to a robust solution for a wide range of hydraulic conditions.
