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 present habitat problems observed in most streams of the basin are often related to excessive sediment in stream channels and/or 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.