Flood Channels: Fish Passage Design Evaluation and Refinement for the Mission Creek Flood Control Channel

A project to provide fish passage in the Mission Creek flood control channel of Santa Barbara, California, has been underway for many years. Flood flows are conveyed through two trapezoidal concrete–lined channel reaches with a combined length of over one mile and present passage barriers to migrating adult steelhead. These passage barriers may lead to complete extirpation of the steelhead populations in the watershed. Therefore, it is necessary to minimize the impact of the barriers on steelhead migration and provide the most favorable hydraulic conditions as practical. The City of Santa Barbara with support from others is planning to modify the two concrete-lined reaches and restore fish passage. Most recently the project has advanced to the final design stage. In the course of detailed design development computational fluid dynamic modeling and other hydraulic analyses were used to optimize fish passage performance, neutralize impacts to flood control and balance sediment transport and associated maintenance requirements. The steps to evaluate and refine the detailed design are presented. The resulting design features are predicted to achieve the objectives discussed previously and are highlighted in this presentation.