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) (Figure 1), resulting in management to insure natural reproduction of native fishes (CADFG, 1999). 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 (Kondolf et al., 1994; Cook and Ellis, 1998; Cook, 2000), and their possible effects on populations of managed fishes.