Santa Paula Creek, located in southwest Ventura County, California, is one of three main historical spawning tributaries for endangered southern steelhead (Oncorhynchus mykiss). Currently, upper watershed habitat that was once accessible to steelhead is blocked by in-channel barriers. Recent floods damaged existing fish ladders and drop structures and escalated existing blockages through the resulting major channel incision and bank erosion.
In an effort to improve fish passage along Santa Paula Creek, Stillwater Sciences, in partnership with RBF Consulting, Inc., is conducting geomorphic, fisheries, and engineering studies to support the development of a detailed watershed assessment and restoration alternatives for future southern steelhead passage restoration in the Santa Paula Creek Watershed.
An important aspect of determining restoration strategies for the fish passage blockages is evaluating the geomorphic conditions in the watershed. Stillwater Sciences assessed both historical and present-day geomorphic processes, and used field observations and literature values to develop estimates of average annual hillslope sediment production and delivery to the channel network. Stillwater assessed current hydrology, bed sediment size, and channel morphologic characteristics to evaluate sediment transport dynamics. These results will provide guidance for improved fish passage, flood control, streambed and bank stabilization in lower Santa Paula Creek.
Stillwater conducted abundance, distribution, and habitat surveys, as well as stream temperature and geomorphic monitoring in preliminary efforts to identify habitat requirements and temperature tolerances of steelhead near the southern limit of their range. Study results combined with existing information helped identify locations that support juvenile steelhead, and determined baseline conditions for steelhead, such as stream temperature, stream drying, and available cover. Relative age class structure was determined through abundance surveys to allow for comparison between habitat and creek types.
Santa Paula Creek historically supported a larger population of southern steelhead than currently exists. A key factor in this decline is migration barriers that exist throughout the watershed.View the gallery