Tioga Creek Instream & Fish Passage Restoration

Tioga Creek is the large tributary that combines with Williams River to form the South Fork Coos River in the Coos basin. The Tioga Creek subbasin is a flashy, coastal system in Coos County that provides important salmon and steelhead spawning and rearing habitat, along with other important species (Pacific lamprey, cutthroat trout); but stream cleaning, riparian logging, road construction, and removal of conifers from side draws have led to decreased wood loading and degraded aquatic habitats. Restoration activities have occurred throughout the Tioga Creek subbasin since 1980s, however recent habitat assessments and project prioritization have led to a collaborative restoration effort by all landowners within the Tioga Creek subbasin for the first time. The Tioga Creek Instream & Fish Passage Restoration project is a multi-faceted project that seeks to address degraded stream complexity, water quality, and fish passage by proposing to 1) place large wood and boulders in Tioga Creek, 2) replace each of the three undersized, double culvert crossings with railroad car bridges to open access to tributary habitat and release a large amount of coarse sediment into the newly added wood structures, and 3) plant conifers along riparian buffer on the Tioga mainstem.

This project reach in Tioga Creek has good intrinsic potential for coho salmon (0.5 and greater) and winter steelhead (0.8 and greater). This project proposes to place ~135 pieces of wood over 2 miles to promote the formation of essential habitat features for these species such as pool scour and secondary channels while encouraging large wood and gravel retention. Over time, these structures will alter and increase the variability in hydraulic conditions resulting in the deposition of coarse sediment, sorting of existing gravels and the development of high velocity refugia and complex pools. Large wood will provide high velocity refugia for juveniles during the winter months through the development of secondary channels, eddies, and alcove and summer time habitat through the development of complex pools and provision of cover habitat. Deposition of coarse bedload material will improve spawning habitat for salmonids, and gravel deposits and large wood structures play a role in the nutrient cycling process, such as nutrient retention and habitat diversity for benthic macroinvertebrates, to improve overall rearing conditions. Ultimately, these cumulative benefits are expected to increase the fish production and population vitality within the Tioga Creek subbasin. The proposed stream crossing upgrades will replace the undersized crossings with bridges that meets fish passage requirements, giving juveniles and adults full access during key migratory periods to 1 mile of tributary spawning and rearing habitat that currently provides excellent off-channel habitat during the winter months. These new bridges will also promote coarse sediment transport into Tioga Creek, a function that is heavily lacking with the current crossings. This will not only increase the amount a gravel reaching the spawning habitat downstream, but it will also decrease channel bed elevations and allow the tributaries to interact with the water table during the summer months, providing more off-channel rearing habitat.