A total of 31 Eastern Subbasin streams were designated as salmonid refugia areas and were rated into one of the four refugia categories. Refugia categories were defined as:
High Quality – relatively undisturbed habitat, with the range and variability of conditions necessary to support species diversity and natural salmonid production;
High Potential – diminished but good quality habitat with salmonids present, currently managed to protect natural resources with the possibility to become high quality refugia;
Medium Potential – degraded or fragmented instream and riparian habitat, with salmonids present but reduced densities and age class representation. Habitat may improve with modified management practices and restoration efforts;
Low Quality – highly impaired riparian and instream habitat with few salmonids (species, life stages, and year classes). Current management practices and conditions have significantly altered the natural ecosystem and major changes are required to improve habitat.
Two of the larger streams, East Branch SF Eel River and Tenmile Creek, were divided into two sections because of significant differences in conditions and salmonid use in upper and lower areas.
Eastern Subbasin streams were generally medium potential and low quality due primarily to lack of canopy, warm water temperatures, and unstable geology. Only one stream in the subbasin was rated high quality: Elder Creek in the headwaters near Branscomb. This stream is located entirely within the boundaries of the Angelo Coast Range Reserve, administered by UC Berkeley as a site for research, education, and public service. Low instream temperatures, good canopy cover, undiverted flow, and minimal road mileage in the watershed, combined with a relatively cool climate influenced by the coastal marine layer, make this excellent salmonid habitat.
Three streams were rated high potential refugia: McCoy Creek, Cedar Creek, and the upper mainstem SF Eel River (beginning at RM 92). Cedar Creek flows primarily through land managed by the USBLM (the Red Mountain Unit), and the dominant vegetation cover type is coniferous forest. This stream contains excellent steelhead habitat, and was chosen as the site of the Cedar Creek hatchery, which operated from 1949-1964. The upper mainstem SF Eel River provides good salmonid habitat due to cool instream and air temperatures (because of the influence of the coastal marine layer), topography that includes many steep walled canyons and narrow valleys, and fewer diversions than in other areas within the Eastern Subbasin.
Six streams in the subbasin were rated low quality: Dean Creek, lower East Branch SF Eel River, Fish Creek, Cummings Creek, Mud Creek, and Cahto Creek were classified as low quality refugia. Most of these creeks are located in residential areas and are heavily diverted. Instream habitat is characterized by high stream temperatures, poor canopy cover, low flow, high sedimentation rates, and poor water quality.
Twenty one streams in the Eastern Subbasin were rated medium potential refugia. Several specific issues include the following:
East Branch SF Eel River above Tom Long Creek (± RM 9) – an excellent steelhead stream with cool water temperatures, but there are low flow issues due in part to diversions;
Bridges Creek – the possibility of completing restoration projects is low due to restricted access;
Rattlesnake Creek – there are passage issues at numerous culverts. Good flow below Elk Creek, with some areas of good canopy cover;
Elk Creek – the culvert under Highway 101 crossing is a total barrier. Flow is a problem due to intense diversion pressure.