Tioga Creek Instream Restoration and Susan Creek Passage Development

Tioga Creek is a flashy coastal system that combines with Williams River to form the South Fork Coos River and provides critical habitat for salmon and steelhead as well as Pacific lamprey and cutthroat trout. It is a BLM Focus Watershed and a high priority subbasin in the 2022 Strategic Action Plan for Coho Salmon Recovery in the Coos Basin due to the high number of high IP miles and anchor habitat for coho, chinook, and steelhead. Susan Creek falls is a two-step bedrock falls that hinders passage and limits the utilization of the 3.5 miles of tributary habitat of Susan Creek. Other past practices such as stream cleaning, riparian logging, and removal of conifers from draws have left degraded aquatic habitats with low wood loading and elevated stream temperatures, leading in the ODEQ 303(d) listing of Tioga. This proposed project will design projects addressing habitat connectivity, stream complexity, and water quality issues to improve critical spawning and rearing habitat in the Tioga basin. To improve critical rearing habitat and habitat connectivity, Coos Watershed Association (CoosWA) proposes to design instream wood structures on mainstem Tioga Creek and passage improvements to Susan Creek falls to improve access at a wider range of flows to habitat within the Susan Creek basin. This project includes an alternatives analysis to assess all passage improvement options for the falls, as well as site designs for mainstem instream restoration to improve stream complexity and water quality on the mainstem Tioga Creek.

Access to tributary habitat is an important component of long-term species viability for Coho and Chinook salmon, steelhead, cutthroat trout and Pacific lamprey. The two-step bedrock falls on Susan Creek significantly delays access to critical habitat during key migratory periods, limiting the use of the upstream habitat. Susan Creek has high wood volumes and percentages of shade and gravel, creating good cold-water tributary habitat, which favors 1+ year rearing life histories of salmonids in the uplands. This project will create designs to improve access to habitat at a wider range of flows, increasing the availability and use of productive summer and winter rearing habitat in the Tioga subbasin. Increasing the quality, quantity, and diversity of spawning and rearing habitats is the best way to improve the resiliency of OC coho. The projects resulting from these designs will also improve instream complexity and water quality by addressing the lack of large wood in the mainstem Tioga Creek. Large wood promotes the formation of pool scour and secondary channels and the retention of gravel and other large wood, provides important high velocity refugia critical for overwintering juveniles, creates complex pools and cover habitat critical for productive summer rearing, and increases the hydraulic variability over time, resulting in coarse sediment deposition and sorted gravels to improve spawning and rearing habitat and decrease stream temperatures during the hot summer months. Large wood and gravel deposits also play a role in nutrient cycling processes, such as nutrient retention and benthic macroinvertebrates habitat diversity, improving overall rearing conditions.