Key Findings

No studies have examined the size or health of salmonid populations in the Eastern Subbasin. However, historical accounts and stream surveys conducted in the 1960s by CDFG indicate that the Eastern Subbasin supported populations of Chinook salmon, coho salmon, and steelhead trout. Recent biological stream surveys indicate the presence of steelhead trout throughout the Eastern Subbasin and coho salmon in a few tributaries. Low salmonid populations throughout the Mattole Basin indicate that salmonid populations in the Eastern Subbasin are likely to be depressed at this time;

Erosion/Sediment
Instream sedimentation in several stream reaches in this subbasin may be approaching or exceeding levels considered unsuitable for salmonid populations. Macroinvertebrates were not sampled in this subbasin. Amphibian sensitive to fine sediment were absent from all stream reaches surveyed in this subbasin;

Riparian/Water Temperature
Available data from sampled streams suggest that high summer temperatures are deleterious to summer rearing salmonid populations in the lower depositional reaches of most streams in this subbasin;

Instream Habitat
In general, a high incidence of shallow pools, a lack of cover, and a lack of large woody debris have contributed to a simplification of instream salmonid habitat.

Gravel Substrate
Available data from sampled streams suggest that suitable amounts and distribution of high quality spawning gravel for salmonids is lacking in this subbasin;

Gilham, Harrow, Eubank, McKee, and Painter creeks are considered good refugia.

In April 2000, a serious diesel spill occurred directly into a subbasin tributary. Petroleum spills represent a chemical threat to favorable stream conditions and should be eliminated using all means available;

Geologic conditions in this subbasin are the most variable in the basin. Areas of relatively intact and stable geologic units are locally interrupted by areas of highly disrupted and unstable soft terrain. These are accompanied by active landslides, gully erosion and, in proximal stream channels, features indicative of excess sediment production, transport and storage in the streams;

Although stream conditions in bedrock reaches suggest that in 1984 this subbasin had the second highest level of impact within the basin, these conditions have improved dramatically in the period between 1984 and 2000. Considering the low degree of impact by features indicative of excess sediment production, transport and storage observed in the adjacent upstream Southern Subbasin, it appears that the stream features observed in the Eastern Subbasin must be derived either internally within the subbasin or from the adjacent Western Subbasin;

As a result of past timber harvest and conversion activities, 56% of the Eastern Subbasin is populated with small diameter forest stands (twelve to twenty-four inches diameter at breast height). Twenty-one percent is in forest stands greater than twenty-four inches. Grasslands occupy 11% of the area;

Over 94% of this subbasin is privately owned. Much of it was sub-divided after extensive timber harvesting. Currently, there is a low level of timber harvest activity;

Existing road densities and locations reflect construction for timber harvest access since the 1940s. Many of these roads are now used to access homes or parcels;

Based on information available for the Eastern Subbasin, the NCWAP team believes that salmonid populations are currently being limited by high sediment levels, high water temperatures, reduced habitat complexity, and embedded spawning gravels in some tributaries of the Eastern Subbasin. Harrow Creek has very good salmonid habitat; Westlund, Gilham, Gilham Creek Tributary, Sholes, Little Grindstone, Harrow, Eubank, McKee, McKee Creek Tributary, and Painter creeks have good canopy density; and Painter Creek has good cobble embeddedness.

Recommendations

Establish monitoring stations and train local personnel to track in-channel sediment and aggraded reaches throughout the subbasin and especially in Mattole Canyon and Blue Slide creeks;

At stream bank erosion sites, encourage cooperative efforts to reduce sediment yield to streams. CDFG stream surveys indicate Middle, Westlund, Gilham, Gilham Creek Tributary, North Fork Fourmile, Sholes, Harrow, Little Grindstone, Grindstone, Eubank, and McKee creeks, and the Tributary to McKee Creek have bank stabilization activities as a top tier tributary improvement recommendation. These could be of localized importance to reduce stream fine sediment levels;

Continue to conduct and implement road and erosion assessments such as the ongoing efforts in the Dry and Westlund planning watersheds. Initiate road improvements and erosion proofing throughout the subbasin to reduce sediment delivery. Middle, Westlund, Gilham, Gilham Creek Tributary, Sholes, Blue Slide, and Fire creeks had road sediment inventory and control as one of their top tier tributary improvement activity recommendations;

Several years of monitoring summer water and air temperatures to detect trends using continuous, 24 hour monitoring thermographs should be done. Continue temperature monitoring efforts in Dry, Middle, Westlund, Sholes, Mattole Canyon, Blue Slide, Eubank, Gilham, and Grindstone creeks. Start temperature monitoring in Little Grindstone, Fire, and Box Canyon creeks;

Where current canopy is inadequate and site conditions, including geology, are appropriate, use tree planting and other vegetation management techniques to hasten the development of denser and more extensive riparian canopy. Canopy density has the lowest suitability for salmonids in Dry and Blue Slide creeks;

Landowners and managers in the this subbasin should work to add more large organic debris and shelter structures in order to improve channel structure, channel function, habitat complexity, and habitat diversity for salmonids. Pool shelter has the lowest suitability for salmonids in Dry, Middle, Westlund, Gilham Creek Tributary, Fourmile, North Fork Fourmile, Grindstone, Little Grindstone, Blue Slide, McKee Creek Tributary, and Painter creeks;

Consider the nature and extent of naturally occurring unstable geologic terrain, landslides and landslide potential (especially Categories 4 and 5, page 89) when planning potential projects in the subbasin;

Encourage the use of appropriate Best Management Practices for all land use and development to minimize erosion and sediment delivery to streams;

Encourage appropriate chemical transportation and storage practices, early spill reporting, and clean-up procedures.

Ensure that high quality habitat within this subbasin is protected from degradation. The highest stream reach conditions as evaluated by the stream reach EMDS and refugia analysis were found in the Gilham, Harrow, Eubank, McKee, and Painter Creeks.