The Chesnimnus Creek Williams Restoration Project is part of a multi-phased effort proposing to complete designs, permitting, and all necessary documents to implement a thoroughly vetted instream and floodplain restoration project benefitting limiting life stages of ESA listed steelhead between RM 4.6 and 9.1 in Chesnimnus Creek. Chesnimnus Creek is a tributary of Joseph Creek, located in the northern end of Wallowa County. Joseph Creek and its tributaries, identified as MCC1 in the Wallowa Atlas Restoration Prioritization Matrix, is a Tier 2 subwatershed. Although the Joseph Creek steelhead population is among the most viable in the region, its headwaters do not originate in high elevation snowpack dominated mountains, which makes this watershed extremely susceptible to changes in temperature and hydrologic regimes.

With legacy logging effects, roads, agricultural practices, and other anthropogenic influences within the Joseph Creek watershed, current habitat conditions in Chesnimnus Creek are significantly deviated from its historic ecosystem function. This departure has negatively impacted many physical and biological aspects of the watershed, resulting in various life stage impairments to steelhead and Pacific lamprey, of which this project aims to improve through a suite of priority restoration actions.

According to the Wallowa Atlas Restoration Prioritization Matrix, the most limiting life stages in MCC1 (Joseph Creek & Tributaries) are Incubation/Emergence, and Summer and Winter Rearing for steelhead. These limiting life stages all rank as a Medium priority, to be addressed within 5–10 years to improve steelhead population productivity, abundance, and distribution. Adult Immigration and Emigration, Holding, Spawning, and Juvenile Emigration all rank as Low priorities, to be addressed in 10–20 years to improve steelhead population productivity, abundance, and distribution.

Riparian Vegetation is ranked as a High priority restoration action for both steelhead and lamprey. Anthropogenic Barriers, Floodplain Condition, Bed and Channel Form, Instream Structural Complexity, and Temperature are ranked as Medium priorities for both steelhead and lamprey. Increased Sediment Quantity is also ranked Medium for steelhead alone. Chesnimnus Creek is among several Joseph Creek tributaries that are currently ODEQ 303(d) listed as “impaired” for both temperature and sediment (ODEQ 2022).

The Wallowa Atlas development team noted that high sediment, water temperature, and habitat fragmentation are all factors contributing to Incubation/Emergence, and Summer Rearing limiting life stages, with particular concern regarding future temperature regime alterations. Another annotation states that Winter Rearing increased in priority due to concerns around losses of winter rearing habitat, specifically on private lands.

The ESA Recovery Plan for NEOR Snake River Spring and Summer Chinook Salmon and Snake River Basin Steelhead Populations (NOAA 2017) ranks the status of the Joseph Creek Steelhead Population – one of four extant populations within the Grande Ronde River Major Population Group, as having a very low risk of extinction. The recovery plan also states, “The recovery strategy will maintain and improve the population’s highly viable status by restoring tributary habitat conditions for steelhead incubation and juvenile rearing”. Decreasing summer water temperatures and minimizing sediment input are listed among the Key Strategies and Actions to be applied in lower Chesnimnus Creek to improve steelhead incubation and juvenile rearing.

All restoration actions implemented through this project will aim to address the highest priority limiting life stages and habitat factors in the Wallowa Atlas Restoration Prioritization Matrix and the ESA Recovery Plan cited above.

The current condition of this reach, and much of lower Chesnimus Creek, is significantly degraded from historic conditions. Due to decades of livestock grazing, channel manipulation, levee construction, vegetation clearing, infrastructure placement, and other anthropogenic interventions, both the stream channel and floodplain have been extremely simplified and disconnected. These land use practices have resulted in loss of off-channel habitat and floodplain connectivity and are the largest factors effecting steelhead incubation and juvenile rearing life stages (NOAA 2017).

The majority of the floodplain under restoration consideration is pastureland, some of which is being used seasonally to graze cattle in the fall. A riparian fence currently runs very close to the creek, which includes intermittent water gaps. These water gaps are located at low gradient sites where steelhead spawning may otherwise occur. However, the channel in these areas has been over-widened, the substrate altered, and redds deposited are subject to trampling by cattle. Additional ecological disfunction, resulting from climate change, was observed in September 2021, where a large reach was dry potentially for the first time on record, according to local US Forest Service staff.

Although there is some remnant beaver activity, beaver colonization in Chesnimnus Creek is severely depleted from historic levels. A marked reduction in diversity and abundance of hardwoods (forage), channelization leading to insufficient pool/ponded habitat (cover), excessive trapping (harvest), and other various impacts have resulted in depressed beaver populations within the watershed, and thus a lack of essential ecological services that beaver provide. Historically, this watershed would have likely been a willow dominated meandering wet meadow complex brimming with beaver dams. This geomorphic and biological combination would have effectively spread out and attenuated water and sediment coming through the system annually during spring high flows. Water captured in the floodplain during these events would have recharged groundwater and intercepted hyporheic flow, proliferating riparian vegetation to the benefit of beaver, fish, and other terrestrial and aquatic organisms through increased food production, reduced sedimentation, and improved stream temperatures and baseflows. In the absence of these symbiotic factors that previously captured runoff, spring flows now flash through the system, and leave much of the watershed hot and dry through the summer and into the fall. These disruptions in natural watershed processes have resulted in deleterious impacts to various life stages of ESA listed summer steelhead - with egg incubation/fry emergence, and juvenile summer and winter rearing being the highest priority, and to a lesser degree, adult immigration, holding, and spawning