Effects of whitewater parks on fish passage: a spatially explicit hydraulic analysis

• Whitewater park (WWP) structures can suppress upstream fish movement.
• Developed a novel continuous description of potential fish swimming paths in a WWP.
• Statistical models based on 3-D hydraulics predict >% of observed trout movements.
• Velocity per body length and depth significantly influence fish passage success.
• Methods provide a powerful, transferable approach to evaluate hydraulic structures.

ABSTRACTEvaluating and designing channel spanning structures for successful fish passage requires description of hydraulic conditions at scales meaningful to fish. We describe novel approaches combining fish movement data and hydraulic descriptions from a three-dimensional computational fluid dynamics model to examine the physical processes that limit upstream movement of trout across 3 unique in-stream structures at a whitewater park (WWP) in Lyons, Colorado. These methods provide a continuous and spatially explicit description of velocity, depth, vorticity, and turbulent kinetic energy along potential fish swimming paths in the flow field. Logistic regression analyses indicate a significant influence of velocity and depth on limiting passage success and accurately predict greater than 87% of observed fish movements. However, vorticity, turbulent kinetic energy, and a cost function do not significantly affect passage success. Unique combinations of depth and velocity at each WWP structure reflect variation in passage success. The methods described in this study provide a powerful approach to quantify hydraulic conditions at a scale meaningful to a fish and to mechanistically evaluate the effects of hydraulic structures on fish passage. The results of these analyses can be used for management and design guidance, and have implications for fishes with lesser swimming abilities.