Fish Passage

A fish barrier is an obstacle that prevents or inhibits the natural migration of salmon, steelhead, and other native fish. These barriers typically include culverts, dams, weirs, and floodgates. Barriers also include natural features such as waterfalls and logjams.

Fish barriers inhibit fish movements by causing not only physical blocks but also changes in the hydraulics of the stream. Improper placement of structures, such as culverts, can cause water velocities to be too high and water depths to be insufficient. These barriers can also cause behavior changes in fish. Barriers can have a significant impact on native fish by restricting migration during spawning. As fish congregate at barriers overcrowding increases the likelihood of stress, injury and predation. Barriers also lead to the under-utilization of the habitat isolated by the barriers. Removal of fish barriers will allow fish and other aquatic creatures to fully utilize the stream and swim freely throughout the watershed.

The County of Santa Cruz Public Works Department in partnership with the Water Resources Program, the Resource Conservation District of Santa Cruz County and funding agencies, have been working to improve passage for fish at county road stream crossing.

In 2004, the County completed an assessment of county road stream crossings: County of Santa Cruz Stream Crossing Inventory and Fish Passage Evaluation (Ross Taylor and Associates) with funding from the California Department of Fish and Game's Fishery Restoration Grants program. This assessment evaluated fish passage at 80 county culverts using a computer program, FishXing. FishXing models hydraulic conditions within a culvert at different flows and then uses fisheries information to determine whether the culvert accommodates fish passage over the desired range of migration flows.

The final ranking included 13 high-priority sites, 13 moderate-priority sites, 27 low-priority sites and 12 sites that met passage criteria. Fifteen sites were dropped from the final ranking because those culverts were not within fish-bearing stream reaches.

Of the thirteen high priority sites, seven sites have been replaced or retrofitted. One moderate priority site has been retrofitted and one moderate priority site has been designed for replacement. Fish passage sites received funding for design, permitting and implementation through the Integrated Watershed Restoration Program (IWRP), funded by the Coastal Conservancy to the Santa Cruz County Resource Conservation District.