Raccoon Creek Watershed Assessment

The County of Placer (County) tasked cbec to lead a project team for a multi-disciplinary assessment of the Raccoon Creek watershed. Hydrologic, geomorphic, water quality, and ecological conditions were characterized in the 112 square mile watershed, starting at the headwaters near Auburn, and extending to its confluence with the East Side Canal along the floor of the Central Valley.

In addition to assessing anthropogenic disturbances and developing and prioritizing restoration and conservation measures, the project also supported the County’s Placer County Conservation Plan (PCCP). The primary objective of the PCCP is to balance development with the conservation of the County’s natural resources, and provide for the protection of sensitive species and their respective habitats. This watershed assessment was a critical first step to these planning efforts.

Given the size of the watershed, cbec developed a spatially nested approach to characterize representative reaches in a diversity of topographic, land use and flow management settings. A fit-for-purpose fluvial audit methodology was employed over 30 miles of stream length to develop a strong understanding of the physical processes and land use and channel engineering impacts operating at both reach and basin scales. Statistical analyses of hydrologic data, coupled with hydrologic modeling, facilitated an understanding of the impacts of flow management and land development on the watershed’s hydrologic regime. To characterize water quality conditions, particularly those vital for salmonids, cbec conducted a spatially and temporally distributed water quality monitoring effort utilizing long-term temperature monitoring, extended water quality sonde deployment, and detailed laboratory sample analysis. To assess riparian and aquatic habitat, HTH implemented California Rapid Assessment Method (CRAM), which provided a framework for the County to monitor changes through time. In addition, surveys were conducted to identify fish passage barriers and determine the distribution and abundance of salmonids through the watershed.

These diverse analyses were leveraged to facilitate a layered GIS analysis to assess the degree of anthropogenic disturbance and the potential for recovery of physical processes and ecosystem health. Emphasis was placed on improving juvenile salmonid (specifically Central Valley Steelhead and Chinook Salmon) rearing habitat and emigration success. These findings were presented to the County in a prioritized portfolio of restoration, conservation, and management actions to facilitate improved ecological and physical health of the watershed. The portfolio featured project concepts and summary sheets for high-priority projects, including fish passage barrier removal and improvement, and stream channel and floodplain restoration actions. The County incorporated the assessment’s findings and recommendations into their final PCCP, which was released in May 2020.

Waterbody / Watershed

Raccoon Creek, Doty Ravine, East Side Canal