Geomorphic Analysis/Assessment of 3 Potlatch River Subwatersheds

A geomorphic assessment was completed for the Corral Creek and Big Bear Creek subwatersheds of the Potlatch River, both Tier 1 priority subwatersheds for wild steelhead habitat restoration. This work assessed 119 stream miles in Corral Creek and nearly 557 stream miles in Big Bear Creek, along with assessing the associated floodplain area in both subwatersheds.



Meadows (wetlands) and floodplains in the Corral Creek watershed were mapped, and landscape units and stream and reach types were identified; a stream power analysis was completed. These components were used to assess the overall watershed/geomorphic condition and to identify the capacity of reach types to adjust and respond to future restoration actions.



In the Big Bear watershed, 109 geomorphic river reaches were identified and characterized, a Morphological Quality Index (MQI) condition assessment was completed, and continuous mapping for valley morphology, floodplain, stream channels, LiDAR derivatives was developed, and LANDFIRE analysis. Maps to illustrate the primary layers used to characterize the watershed and reaches and results of the assessments were created. Individual GIS layers from this effort help describe specific morphological features and characteristics within each reach and will support future restoration and conservation planning within the basin.



This proposal originally requested funding to complete a third geomorphic assessment of East Fork Potlatch River. Once the contracting process began it was determined that the original proposed budget would not be sufficient to cover this cost. As a result, a modification was made to the original project scope to only include Corral Creek and Big Bear Creek. All metrics identified for Corral Creek were satisfied. In Big Bear Creek, the metrics for stream miles assessed that.... were put in as zero, although in reality these should be NA as no stream miles were assessed for these specifics. The metric for fish passage barrier inventory was not completed due to budget constraints.



Both reports will be posted on the Clearwater Focus Program website: https://species.idaho.gov/programs/clearwater-focus-program/

The atlas of maps to be produced through the geomorphic analysis and assessment will provide a foundation to guide strategic planning by Potlatch Implementation Group participants to identify and prioritize projects areas and the respective priority process-based restoration strategies to improve instream habitat, steelhead production and steelhead productivity, and work sequencing for implementation years 2023-2027 and beyond. The Tier 1 priority subwatersheds and priority process-based restoration strategies have been identified in the 2018 draft amendment to the Potlatch River Watershed Management Plan; an implementation plan for 2018-2022 has been developed as part of the 2018 amendment. The five year implementation increments will also align with the NMFS Recovery Plan and NMFS’s five year implementation plans to track recovery of Snake River salmon and steelhead.