Middle Subbasin streams provide important spawning and rearing habitat for anadromous salmonids. Steelhead and coastal cutthroat predominate in the tributary streams year round while Chinook depend mostly on the mainstem for spawning habitat and temporary juvenile rearing. Coho once noted as present in some tributaries were not observed during 2001 surveys. Summer steelhead are likely the most threatened salmonid stock inhabiting the Redwood Creek Basin.
The mainstem Redwood Creek has slowly adjusted from destructive impacts related to intensive land use and the 1964, 1972, 1975 floods. These storms occurred during an era when much of the Redwood Creek basin was undergoing unregulated timber harvests. Timber harvest activities contributed to destabilization of the land and increased runoff rates causing severe erosion, and severe damage to Redwood Creek including aggradation, widened channel, streambank erosion, and filling of pools with sediments. Presently, sediments are moving from the active channel of tributaries and upper and middle reaches of Redwood Creek, but they tend to accumulate in lowest gradient and unconfined reaches. An increase in channel structure has recently been observed, however this has not occurred without setbacks related to landslides induced by moderate storm events. Because of the combination of natural instability across the Middle Subbasin, legacy land disturbances effects, and land use that results in new ground disturbance, winter storms still pose risks for excessive erosion and sediment inputs to anadromous salmonids streams. This was shown during the winter of 1997 when an increase in landslides and associated sediment inputs were measured at RNSP cross sections.
High water temperature is likely the most limiting factor to salmonid production in mainstem Redwood Creek. The high water temperature is related to the lack of shade over the water along middle and upper mainstem reaches. Other significant factors affecting salmonids production in the mainstem are related to excessive sediment inputs and include lack of pools and lack of instream shelter complexity. Trees large enough to function as LWD, need to be allowed to grow and recruit to stream channels from riparian and near stream forest areas. Tributary streams generally provide good water temperature, except in lower reaches of Lacks and Minor creeks. Tributaries also showed a lack of deep pool habitat and instream shelter complexity.
The Middle Subbasin offers opportunities for implementing watershed habitat improvement activities. Watershed management strategies aimed at reducing erosion and developing functional near stream forests will help address landscape issues. This will help to reduce water temperature, increase bank stability, provide a source of LWD, and reduce sediment inputs to stream channels. Stream habitat improvement activities should focus on increasing depth and complexity to existing pool habitats, and adding shelter complexity to cool water refuge sites.