Flow Simulation in a Rock-Ramp Fish Pass

The flow characteristics in a rock-ramp fish pass can be significantly altered by the boulder arrangement. This study used a three-dimensional computational fluid dynamics solver to investigate flow characteristics for variations of discharge, channel slope and boulder size, spacing, and pattern. This study derived relationships for estimating water depth and velocity in a rock-ramp fish pass as a function of discharge and structure geometry. The flow resistance varies significantly with emergent boulder spacing and is nearly constant for submerged boulders. This study derives relationships for the drag coefficient and submergence ratio to forecast average flow velocity using a flow-resistance equation. Based on maximum velocity and a slow velocity zone, this study recommends effective boulder spacing in the longitudinal and transverse directions for two different boulder patterns. Finally, this study developed a design procedure for designing a rock-ramp fish pass.