Hat Creek is one of the most famous “spring-river” fly fishing destinations in North America. The lowest 5.5 kilometers of the creek are designated a “Wild Trout Area” (WTA) by the California Department of Fish and Wildlife (CDFW), resulting in management to insure natural reproduction of native fishes. However, since the late 1970’s, declining aquatic habitat quality and resulting fishing opportunities throughout the Hat Creek WTA due to sedimentation issues have prompted assessments of hydrogeomorphic process and conditions in lower Hat Creek, and their possible effects on populations of managed fishes.

Declining fishing conditions through the Hat Creek WTA are largely attributed to segment-scale sedimentation problems and resultant loss of formerly dense beds of aquatic vegetation that provided the dominant structural habitat for aquatic invertebrates and wild trout. Additionally, it is suggested that burrowing muskrats have degraded stream banks, resulting in channel widening and the introduction of additional sediment loads to Hat Creek. The combined losses of aquatic vegetation, channel bed aggradation and channel widening have led to the development of wide and shallow channel reaches with diminished aquatic vegetation cover relative to historical conditions. These aquatic habitats are poorly suited for wild trout, and thus have prompted recent efforts to restore aquatic habitat in select reaches within the WTA.

Through consultation with CDFW, California Trout (Cal Trout) initiated a “pilot” restoration project within the Carbon Reach of the Hat Creek WTA in October 2015. The focus of this pilot project was the introduction of large woody debris (LWD) structures to help stabilize fine sediment, increase spatial variability in flow velocities and depths, and also provide overhead cover to wild trout. Using high-resolution velocity and topographic data collected prior to and following the installation of LWD structures in Hat Creek, the UC Davis Center for Watershed Sciences evaluated hydraulic and geomorphic changes to the Carbon Reach associated with the restoration activities.