Upper Sonoma Creek Watershed Salmonid Habitat Enhancement Sites: Working within a Hydrologically Diverse System- Successes, Land Owner Objectifications, Modifications, and New Technical Considerations
Wednesday, March 7

Field Tour Leaders: Lisa Micheli, Restoration Program Manager
Will Pier, Fisheries Restoration Specialist
Mark Newhouser, Riparian Restoration Specialist

This field trip will guide participants to a series of large woody debris and boulder installation sites in Sonoma Valley located on two major tributaries of Sonoma Creek. These projects were installed based on CDFG protocol with the aim of enhancing pool habitat. Participants will have the opportunity to see how these projects performed under the pressure of a rare flood event. These projects also display innovative approaches to enhancing the aesthetics of installations.

Topographic surveys before and after installation of large woody debris (LWD) provide a basis for evaluating implementation success and for refining our understanding of how these types of projects may perform in a range of environments. The Sonoma Ecology Center installed a number of LWD fish habitat structures in 2003. Creeks treated included the main stem of Sonoma Creek and two tributaries (Graham and Calabazas Creeks). Cross sections and longitudinal profiles for these projects were resurveyed in 2006, following the flood of record on Sonoma Creek (at least a 50-year return interval event).

Sonoma Valley is a high sediment yield watershed largely due to volcanic parent material (the Sonoma Volcanics geologic unit). Project impacts on channel morphology were a function of resulting erosion or sediment storage on-site. While pool scour is the typical objective of projects following Department of Fish and Game protocols, we found that in some cases projects were quite efficient at trapping gravels and cobbles. The result was increased spawning habitat availability at affected projects sites. This result strengthens our hypothesis (based on geomorphic surveys conducted for a Limiting Factors Analysis) that the paucity of spawning gravel availability in Sonoma Valley tributaries may be linked to low densities of large woody debris.

Some sites were modified due to landowner concerns about the aesthetics of LWD and boulder installations. Sub-urban/ rural streams of Sonoma Valley with highly visible habitat restoration sites require natural looking, lower impact designs. This requires working closely with landowners during design stage, greater care during installations, frequent irrigation of revegetation during dry months, and monitoring after high flow events to assess for LWD losses and changes.