Management Issues

Salmonid populations have declined from historic levels, prompting listings under the state and federal ESA’s.

Impairments to freshwater and estuarine 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 Redwood Creek Basin has large areas with highly unstable slopes.<

Land use has made the basin’s terrain more susceptible to erosion.

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

Basin management goals.

Planning Watersheds in Redwood Creek are not always composed of logical hydrologic units.

Findings Related to Issues

Salmonid populations have declined from historic levels, prompting listings under the state and federal ESA's:

Redwood Creek’s anadromous salmonid stocks should be viewed as critically valuable natural resources;

Present anadromous salmonid populations are less abundant and less widely distributed compared to their historic presence in the Redwood Creek Basin;

Increasing the abundance, diversity and distribution of Redwood Creek’s salmonid stocks are vital steps towards the restoration of viable salmonid populations to California;

The capacity for salmonids to increase in abundance and distribution is in part limited by the reproductive potential of existing stocks;

Sport and commercial fish harvests have played a role in the reduction of Redwood Creek’s salmonid populations, but persistent impairments to critical habitat are likely most responsible for their decline;

Given improving aquatic habitat conditions, it will likely take several generations before salmonid populations rebound to viable levels.

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

Primary causes for stream habitat deficiencies can often be traced back to land management actions that increase erosion, or activities that alter characteristics of near stream forests;

Many of the adverse changes to stream habitat conditions have been exacerbated by winter floods and summer droughts;

the lack of a large conifer component in nearstream forests;

Warm water temperature in mainstem Redwood Creek limits salmonid production in most of the Upper Subbasin and all of the Middle and Lower subbasins;

Many tributaries across the basin have cool water temperatures but often lack the combination of structural components that create the habitat diversity and complexity needed by salmonids to support abundant populations;

An additional factor affecting salmonid production is the large reduction in area and habitat quality of the estuary/lagoon;

Excessive sediments inputs can result in several adverse and long lasting impacts to salmonid habitat including impaired spawning habitat, a decrease in the numbers and depths of pools, increases in stream width and decrease in stream depth;

The negative impacts from excessive sediments are in some cases exacerbated by the general lack of instream large wood debris (LWD) needed for pool scour and sediment routing processes;

Instream LWD is low in abundance in Redwood Creek streams in the Estuary, Lower, Middle and Upper subbasins;

As a result of timber harvests and stream bank erosion, there is a low potential for near term LWD input to several anadromous reaches in the basin;

More LWD is needed in many stream channels to help in the formation and maintenance of pools, providing shelter for fish, facilitate sediment routing, and to provide nutrient inputs.

The Redwood Creek Basin has large areas with highly unstable slopes:

Faulting dominates the geomorphology of the basin;

Natural geologic instability contributes to large inputs of sediment to the basin’s stream network;

The region experiences a high level of seismic activity, and major earthquakes have occurred along the Cascadia subduction zone as well as within the individual tectonic plates and along well-defined faults;

High rates of regional uplift provide a continual source of large amounts of sediment to the basin;

Much of the naturally occurring erosion resulting from slope instability has been compounded by human activities.

Land management on unstable slopes often exacerbates slope instability and the release of sediment. Relatively minor land use actions, such as undercutting the toes of slopes, increasing the duration of ground saturation, or reducing soil shear strength by a relatively small amount, could trigger extensive landslides.

Land use has made the basin’s terrain more susceptible to erosion:

The combination of naturally unstable terrain and infrequent, unusually severe storms (such as the one that occurred in northern California in December 1964) and intensive timber harvesting can trigger major episodes of erosion;

There are high road densities in much of the basin and large amounts of sediments are generated from road related failures especially from roads located on steep, unstable slopes;

Fine sediment accumulations in stream channels are typically more abundant where land use activities such as road building or land clearing expose soil to erosion and increase mass wasting;

Many of the effects from land use activities on upland sediment sources are spatially and temporally displaced from response reaches;

Past fluvial erosion was accelerated by land use and this erosion could have been minimized with better erosion-control and road-maintenance measures;

High turbidity levels in Redwood Creek are believed to occur more frequently and persist longer than observed in the past.

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;

As trees grow and become subject to harvest, how will management protect valuable aquatic and fishery resources from similar impacts as occurred in past years?

Shade over the water from willow and alder riparian vegetation alone is not enough to keep water cold;

Micro-climate benefits provided by near stream forests and overstory shade are important to help maintain cool water temperature.

Basin management goals:

It is important to note that without management strategies that promote restoring integrity to watershed ecosystem process by addressing root causes of problems, instream improvement projects will likely be short-lived patches on the environment.

Management strategies should take a basin-wide perspective;

Retention and recruitment of large trees is needed along streams;

Stream condition improvement and increasing anadromous salmonid populations largely depends on achieving a balance between the socio-economic needs for timber resources and management needed to maintain or improve basin conditions that sustain viable fish populations;

The Redwood Creek basin is an excellent candidate for a successful long-term, programmatic watershed improvement effort. Most of the basin has a high potential to improve fish habitat conditions. Reaching that goal is dependent upon the formation of a well organized and thoughtful improvement program founded on broad based community support for the effort.

Planning Watersheds in Redwood Creek are not always composed of logical hydrologic units.

Planning Watersheds often cross the Grogan fault and include different geologic units having diffferent physical characteristics and different mass wating potential;

Analysis of such units are compromised by the high variation between east and west side geology.

Recommendations

Perched Sediment Delta
Perched sediment delta at mouth of Panther Creek impedes
upstream migration of coho to spawning grounds.

Large Debris Accumulation
Large debris accumulation near mouth of Lake Prairie Creek.
This migration passage barrier formed from a debris torrent in 1997.
Barriers to Fish Passage

Fish barriers were found at culverts, perched sediment deltas,
or boulder and/or debris accumulations.

Facilitate fish passage at sites that may impede upstream fish passage into tributary streams for spawning or downstream movements.

Flow and Water Quality Improvement Activities:

Water flow does not appear to be and issue at this time over most of the basin. However, fish habitat requirements and channel maintenance flows should be considered prior to any water development projects including riparian diversions and small domestic water use;

In order to help reduce water temperature in tributaries and the mainstem, ensure that near stream forest management encourages growth and retention of conifers sufficient for providing shade and cool micro climate benefits to stream and riparian zones;

Consider using willow baffles, tree planting or other applicable methods to promote effective shading from riparian trees and to reduce the channel width along reaches of Redwood Creek;

Timber harvests or other land use should be conducted in a manner that does not increase peak flows, accelerate runoff rates, or deliver excessive sediment to stream channels;

Erosion and Sediment Delivery Reduction Activities:

Existing sediment production problem sites that have potential to deliver sediments to streams should be evaluated and mitigated;

Since timber harvesting and other land use can cause disturbances that may contribute to slope instability, management on slopes with high landslide potential and/or on lands adjacent to streams should first involve a risk assessment or be avoided. Determination of appropriate practices should be made through the use of the CGS landslide and landslide potential maps, in conjunction with site-based geological examinations by licensed and appropriately trained geologists;

For timber management on steep and/or potentially unstable slopes (in many cases, slopes greater than 35%) we recommend use of lower impact silvicultural prescriptions to maintain vegetative cover and the use of cable or helicopter yarding to reduce the potential for erosion and sediment production, which can result in sediment accumulation in Redwood Creek;

Landowners should continue road erosion hazard surveys throughout the basin and use this information to set priorities for road removals and upgrades, and implement these improvements as rapidly as private and public funding allow. Roads located on unstable slopes and roads near streams should receive high priority for survey and upgrades and decommissioning projects;

Consider avoidance or mitigation for risks of excessive erosion when planning, building or removing roads in or near deep-seated landslides and earthflows;

Reduce road density across the basin especially in the Middle and Upper subbasins;

If new roads need to be constructed, they should be designed to prevent erosion and not be located near the valley bottom where they may pose a high risk of generating sediment delivery to streams. Consider locating roads along ridge tops where feasible;

The use of fire for site preparation purposes should be minimized on schist soils during warm, dry periods (late summer and fall).

Riparian and Stream Habitat Improvement Activities:

To increase shade canopy, promote growth and retention of large conifers in the riparian corridor along mainstem Redwood Creek;

Where current near stream forest canopy is strongly dominated by hardwoods and site conditions are appropriate, land managers should consider cautious thinning of hardwoods from below to hasten the development of denser and more extensive coniferous canopy component;

To address the lack of large woody debris in many tributary channels and along the Redwood Creek mainstem, management should promote growth of near stream conifers and allow natural recruitment of trees to stream channels;

Where near stream conifers are not large enough to function as naturally occurring scour elements, consider importing LWD from nearby hillslopes for placement in locations and orientations where it will provide beneficial habitat elements and will not accelerate adverse bank erosion;

Add combinations of boulders and LWD to increase shelter complexity to cool water patches located in Redwood Creek. The cool patches may be located in temperature stratified pools or adjacent cool water inputs from springs, seeps and tributary flows;

For timber harvest plans in the Upper and Middle subbasins, consider additional measures to increase function of watercourse protection zones when justified by lack of large conifers to provide shade and microclimate, lack of instream LWD, and low LWD loading potential;

Consider the use of conservation easements or other management strategies to maximize potential benefits to aquatic habitats from near stream forest protection along the middle and upper reaches of Redwood Creek;

Consider limiting cattle access in streams where their presence has caused significant bank erosion and impaired growth of vegetation;

Prescribed fire use within the Redwood Creek basin could reduce adverse impacts to watercourses and wet areas. Regular use of prescribed fire could reduce fuels so that catastrophic fires are less likely to occur.

Monitoring, Education and Research Activities:

Develop Planning Watersheds that are defined by logical hydrologic units; br />
Utilize CalVeg GIS layers to locate areas where coniferous trees are too small to provide beneficial functions of LWD loading. These areas should be considered for LWD addition to stream channels if needed to retain and promote desirable pool characteristics, sediment routing and other channel maintenance processes;

Temperature monitoring by land owners and responsible agencies should continue at current and additional sites to extend trend lines and track changes that may impact salmonids or that may indicate a status change. The establishment of trend lines from these data will aid in future studies, validate improvements from forest and stream recovery and will be helpful for habitat improvement project effectiveness monitoring;

Monitoring suspended and in-channel stored sediments by sampling sediment size distribution, turbidity, V*, photo points, etc. should be continued, and tracking of streambed levels with stream channel cross sections should be continued by responsible agencies and landowners;

A long-term, concerted monitoring effort among the land owners, interested parties and responsible agencies is needed to determine the status and trends of anadromous fish populations of Redwood Creek. Efforts should include annual spawner surveys, weir counts, summer steelhead dive counts and monitoring juvenile populations;

Biological monitoring, particularly for aquatic insects and aquatic food web dynamics, will be an important addition to monitoring efforts in the Redwood Creek basin;

Ensure that CEQA-compliant environmental assessment is conducted prior to issuance of the Fish and Game Code 1600 series streambed alteration permits and Corps of Engineers or NOAA Fisheries permitting requirements are complete for significant projects on streams of Redwood Creek;

It is unclear whether modern timberland management practices will allow full restoration and recovery of desirable watershed ecosystem function. Conservation easements that provide wider buffers along water courses or additional management measures may be needed to provide the protection needed to promote watershed and aquatic ecosystem recovery;

CDFG stream habitat surveys provide information only for reaches accessible to anadromous salmonids. Additional surveys above the limits to anadromy are necessary to identify upstream conditions that affect anadromous reaches such as riparian canopy status or additional sediment delivery sites that may benefit from erosion control treatments.