Contract Description:
The Lower Limber Jim Creek Restoration Project is located on Limber Jim Creek, tributary to the Grande Ronde River. The project is located on approximately .6 mile of Limber Jim Creek (RM 0 - .6). Limber Jim Creek is spawning and rearing habitat for Snake River Basin chinook salmon, summer steelhead, bull trout and redband trout. Historic timber harvest and grazing, roading and mining reduced the future recruitment of large wood and the amount/types of riparian vegetation. These combined impacts also changed pool/riffle ratios, residual pool depth, habitat complexity, and floodplain function. The project would place wood within .6 mile of Limber Jim Creek. All disturbed areas will be seeded and mulched after project completion. Monitoring will include established photo points. Project partners include US Forest Service, Bonneville Power Administration and Grande Ronde Model Watershed.
Overall Problem: Lower Limber Jim Creek and its meadow habitats are not in proper functioning ecological condition (hydrologic, geomorphic, vegetative composition), due to historic management that included beaver trapping, over grazing, logging, road building, and an altered fire regime.
Sub-problem 1 - Floodplain form and function has resulted in:
• decrease in water storage and meadow/wetland habitats, resulting in drier site and mesic-site species encroachment. Drier habitats are less conducive to riparian deciduous woody vegetation species (Populous and Salix) that are important food and habitat for beaver populations.
• potential increase of in-stream water temperatures from a decrease in groundwater recharge, which can be problematic for salmonids,
• increase of in-channel velocity where the channel has downcut, and doesn't spread water out onto the floodplain during high flows. The process of downcutting causes vertical erosion, which increases fine sediment levels and decreases habitat complexity.
• decrease in the amount of of zero velocity habitat, which provide juvenile salmonids protection, temperature buffering, food sources and feeding areas, and resting areas.
Sub-problem 2 - Fish habitat complexity (cover, pool quality/quantity, zero velocity habitat, and spawning gravel recruitment) is limited.
• Channel incision and lack of instream woody material has affected the quantity and quality of spawning, rearing, and overwintering habitat in Lower Limber Jim Creek.
Overall Goal: To achieve proper ecological form and function of Lower Limber Jim Creek and its meadows, and restore habitat for the Snake River Basin Spring/Summer Chinook and Snake River Basin Steelhead.
• Restore Hydrologic Function In the meadow reach (Rosgen channel type C and E) increase hydration of laterally confined channel to improve groundwater retention. Use Large Woody Debris (LWD) to restore stream grade, reduce hydraulic efficiencies, and increase floodplain meadow inundation time. LWD structures will be placed in locations to increase roughness and back up water.
• Improve Fish Habitat Restore channel habitat complexity. LWD structures will be constructed. These structures will enhance scour pool habitat, cover, and floodplain connection. The structures will increase hydraulic complexity and zero velocity refugia on active channel margins