Issues

Impairments to freshwater habitat needed to complete salmonid freshwater life cycles have been identified as a leading factors in the decline of Redwood Creek’s anadromous salmonids.

The Upper Subbasin is highly susceptible to erosion.

Land management can influence watershed processes.

Riparian and near stream forests have been altered by timber harvests and bank erosion.

Impairments to freshwater habitat needed to complete salmonid freshwater life cycles have been identified as a leading factors in the decline of Redwood Creek’s anadromous salmonids.

Findings

Impairments to freshwater habitat needed to complete salmonid freshwater life cycles have been identified as a leading factors in the decline of Redwood Creek’s anadromous salmonids:

Mixed conditions for salmonid spawning and rearing success exist in the subbasin;

There is a lack of shade canopy along mainstem Redwood Creek;

High summer water temperature along the mainstem Redwood Creek impairs juvenile rearing habitat and adult holding habitat for summer steelhead;

There is a lack of deep and complex pools in tributary streams and mainstem Redwood Creek;/li>

A lack of instream LWD impairs fish habitat;

Stream habitat conditions in the Upper Subbasin can be improved.

The Upper Subbasin is highly susceptible to erosion:

Seventy-two percent of the subbasin has high or very high land slide potential;

Land use such as timber harvest activities exacerbate erosion potential;

Recently the Upper Subbasin has produced more sediment than the Middle and Lower Subbasins combined;

The Upper Subbasin generates and exports sediments that contribute to aggradation and persistent impairment of salmonid habitat in the Lower and Estuary subbasins.

Land management can influence watershed processes:

Land uses, such as timber harvest activities, increase erosion potential over much of the Upper Subbasin;

High road density of both abandoned and useable roads adds to instream sediment delivery potential;

Debris slides and debris flows are often initiated by management activities (such as road construction) that take place on existing earthflows or rockslides.

Riparian and near stream forests have been altered by timber harvests and bank erosion:

Timber harvests have caused significant levels of disturbance to riparian and near stream forest areas causing a reduction in both overstory shade canopy and LWD input potential;

In response to aggraded channels, stream banks erode, channels widen, and riparian vegetation becomes less affective to provide shade over the water.

Impairments to freshwater habitat needed to complete salmonid freshwater life cycles have been identified as a leading factors in the decline of Redwood Creek’s anadromous salmonids:

The water temperatures increase quickly to above desirable levels in the upper mainstem Redwood Creek due to the widened stream channel and lack of riparian shade canopy;

Water temperature in monitored tributary streams is generally suitable for anadromous salmonids;

Mainstem Redwood Creek, Fern Prairie Creek and Minon Creek provide some deep pools, but these streams are below desirable target levels for amount of deep pool habitat;

Instream shelter is lacking in Redwood, Minon, and Fern Prairie creeks.

Recommendations

Barriers to Fish Passage

Modify sediment deltas or boulder and/or debris accumulations that impede upstream migration into tributaries. A barrier is located at the confluence of Lake Prairie Creek. Consider modifying debris accumulation and building step pools in the lower reaches where sediment accumulations may restrict or delay access to migrating salmonids.

Flow and Water Quality Improvement Activities:

Maintaining and improving good water temperatures in tributaries and in the upper reach of Redwood Creek is essential to improve of salmonid habitat condition in the Upper Subbasin and also will provide benefits to downstream reaches;

A high priority should be placed on re-establishing riparian shade and reducing the channel width along portions of the upper reach of Redwood Creek. This will help extend the benefits of cool water flowing from the headwaters reach.

Riparian and Instream Improvement Activities:

In appropriate locations along the upper reach of mainstem Redwood Creek, consider installing live willow baffles or other habitat structure to help establish shade over water and to encourage channel width reduction;

The riparian corridor and near stream forest along the upper reach of Redwood Creek should be managed to encourage growth and retention of coniferous trees. The shade provided by large trees will help maintain cool water temperatures, their stems will provide large woody debris and provide nutrient inputs to the stream, and roots will add stability to banks and buffer against sediment delivery. This may require more than the minimum protection provided by Forest Practice Rules;

In tributaries with an abundance of shade, consider cautious thinning from below in riparian areas to hasten the development of large near stream conifers;

Design and engineer pool enhancement structures to increase the number of pools or increase the size, deepen, or add shelter complexity to existing pools in Redwood Creek and Fern Prairie Creek and Minon Creek and other tributaries;

Consider adding shelter complexity with wood and large boulders to existing cool temperature refuge sites on upper Redwood Creek. This could be done on a seasonal basis using small woody debris to provide escape cover for adult summer steelhead and juvenile salmonids during summer season. The cool patches may be located in temperature stratified pools or adjacent cool water inputs from tributary flows, springs, and seeps;

To address the lack of complex pools add, large woody debris in Redwood and Minon and Fern Prairie creeks, consider direct placement of large woody debris in existing pool habitat, especially where the average size of near stream conifers is less than 2 feet DBH;

Consider the use of conservation easements along the upper reach of Redwood Creek to protect valuable riparian and near stream forest from development or timber harvests.

Erosion and Sediment Delivery Reduction Activities:

In streams where the majority of pool tail spawning substrate is highly embedded with fine sediment, sediment sources should be located, rated according to their potential sediment yields, and treated;

Upgrade or decommission roads in accordance with existing or future road assessment surveys, especially roads located on unstable slopes and roads near streams. These are found throughout the subbasin but are most frequent in Windy Creek, Twin Lakes Creek, Bradford Creek, and High Prairie Creek Planning Watersheds;

Consider bank stabilization projects in tributary streams throughout the Upper Subbasin;

Throughout the Upper Subbasin, timberland managers should avoid the use of tractor yarding on slopes steeper than 35% (19 degrees) and instead use full suspension cable or helicopter yarding on steep and/or highly unstable slopes.

Education, Research, and Monitoring Activities:

Conduct stream surveys in tributaries and mainstem reaches not addressed in this report;

Continue temperature monitoring at the current locations to observe changes in temperature as effects from mainstem fluvial conditions, such as aggradation, degradation, channel widening, and riparian function adjust through time;

Monitoring for in-channel sediment (e.g., sediment size distribution, turbidity, V*, photo points, etc.) should be continued and tracking of streambed levels (i.e., stream channel cross sections) should be continued at upper Redwood Creek study sites;

A long term, concerted monitoring effort between the land owners, interested parties and responsible agencies is needed to determine the abundance and trends of anadromous fish populations of Upper Subbasin streams;

Summer steelhead dive counts should be conducted on an annual basis along the upper reach of mainstem Redwood Creek.