Session B5 - Culvert Roughness Elements for Native Utah Fish Passage

Fish passage designs for culverts rely mainly upon the comparison between the average flow velocity and the sustained swim speeds of fish, a method developed by studying salmonid species and their swimming patterns. This method does not recognize the role of reduced velocities near boundaries. Laboratory and field tests have been performed to test the use of these reduced velocities by several native Utah fish: leatherside chub (Lepidomeda aliciae), longnose dace (Rhinichthys cataractae), and speckled dace (Rhinichthys osculus). Laboratory flume tests were conducted using leatherside chub and longnose dace with three boundary conditions: a smooth boundary, a smooth boundary with strategically placed and sized cylinders, and a boundary consisting of natural substrate collected from the field. The key finding from these tests was that substrate that scaled with the fish length required the least energy expenditure, provided sufficient refuge to allow the fish to behave naturally, and allowed for successful passage. Field tests were performed in a southern Utah stream (Salina Creek) with speckled dace and leatherside chub. Fish were captured, marked, and recaptured at three locations: an arch culvert with a coarse substrate bottom, a double barrel concrete box culvert, and a stream section between the two culverts. Results showed that passage alone was not an adequate indicator of ability since not all fish attempt to pass upstream. Instead, population estimates within each of the sites were calculated to estimate use and the quality of habitat within the culverts. Population estimates were slightly higher at the arch culvert site than at the box culvert site. Velocity measurements were also taken near the boundary at each site to characterize the amount of variation within the culvert and population estimates correlated to the amount of variation found at each site. Providing fish with velocity variation by placing substrate instead of simply matching the average flow velocity to their swim speed may allow more fish to pass upstream and use the culvert as habitat rather than treating it as a barrier