Fish Passage

A fish barrier is an impediment 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.

2023 Inventory of Historical Structures and Anadromous Fish Passage Conditions in the San Lorenzo River

This report provides an inventory of historical, anthropogenic (human-constructed) structures on the San Lorenzo River that affect fish passage. These historical structures affect upstream and downstream passage for adults and juveniles, especially during dry years or periods of low base flow in the river. This study focused on documenting 37 historical structures that completely or partially span the San Lorenzo River. Of those 37 historical structures, 24 structures span the channel and substantially affect fish passage.

This report recommends the removal or modification of channel-spanning historical structures that substantially affect fish passage. Specifically, this report recommends that the County, CDFW, and NOAA Fisheries work together to facilitate the removal or modification of historical structures rated as Medium or High Passage Severity.

County of Santa Cruz Stream Crossing Inventory and Fish Passage Evaluation

In 2002, the County received a grant from the California Department of Fish and Wildlife Fisheries Restoration Grants Program to identify, assess and prioritize county culvert stream crossings for fish passage.  In 2004, Ross Taylor and Associates produced the final report: County of Santa Cruz Stream Crossing Inventory and Fish Passage Evaluation.  The report identified 13 high priority sites, 13 moderate priority sites, 27 low priority sites and 12 low priority sites with a “green” passage rating.

The County of Santa Cruz completed 14 fish passage projects between 2003 and 2014, including 11 projects at county culvert stream crossings.  Of the 13 High Priority Sites identified in the 2004 Ross Taylor report, 7 projects have been completed.  Of the 13 Moderate Priority sites, 3 projects were completed.  Of the 27 low priority sites, passage at one site was completed when the culvert was repaired following storm damage.   In addition to the culvert projects, the County of Santa Cruz completed an additional 3 fish passage projects: (1) at Carrol Avenue bridge on Lompico Creek, (2) a Caltrans culvert on Valencia Creek and (3) the removal of a sewer line across Aptos Creek at Spreckels Drive.   Most of these projects were completed through the Integrated Watershed Restoration Program (IWRP), coordinated by the Resource Conservation District of Santa Cruz County.

In 2022, an update report was completed that builds on the 2004 Ross Taylor report and identified new priority projects.  This report identifies 13 High Priority projects that include 2 locations damaged in the 2017 storms, 6 locations in 3 watersheds (Liddell, Lompico and Casserly) and 5 locations for adaptive management of completed projects.