Asotin IMW Monitoring 2017

The Asotin Creek Intensively Monitored Watershed project (Asotin IMW) has been running since 2008 with the goal to test the effectiveness of low-tech process-based restoration structures at improving riverscape health and summer steelhead productivity. The project is coordinated by the Snake River Salmon Recovery Board and funded by the Pacific States Marine Fisheries Commission. This report summarizes the final design and as-built construction details for increasing wood densities in the Asotin IMW funded by RCO Grant 17-1304. Grant 17-1304 was originally developed to support monitoring and analysis efforts for the IMW, but was amended to focus more on maintenance and enhancement actions in the IMW treatment sections and updating enumeration of emigrating steelhead smolts, adult escapement, and smolts per spawner for each IMW stream and treatment and control section. Originally, we installed 654 post-assisted log structures (PALS) between 2012-2016 and have seen some positive geomorphic and fish population responses. As part of our adaptive management plan, we have conducted annual structure surveys and have thresholds that trigger the addition of more wood if the density in treatment sections does not remain high. We added additional wood to increase the treatment wood density in 2016, 2018, and 2020 based on the annual surveys. We increase wood density by adding more wood to structures that lost wood, rebuilding structures that were washed downstream, and other low-tech restoration approaches like harvesting trees on site or using grip-hoists to move downed wood into the stream. Surveys in spring 2020 and 2021 identified areas in each original treatment that could be enhanced with more wood. In this report, we document enhancing 131 structures with the addition of over 300 pieces of LWD, whole trees, and small woody debris. Most of the large wood and trees was added to the North Fork Asotin Creek using wood harvested onsite to rebuild or enhance 39 PALS. We also built 25 BDAs in Charley Creek and connected over 500 m of side-channels. We took advantage of abundant SWD that was available along South Fork from fire line construction and added brush and small trees to over 60 existing structures in South Fork Creek. This report includes the final restoration design and as-built descriptions of the methods, structure locations, construction actions, and a summary of analysis methods and estimates of steelhead smolt emigration and adult escapement from 2008-2020 for the IMW streams and treatment and control sections. Interpretation of the smolt and adult estimates will be presented in the IMW annual report for 2021 (SRFB Project 19-1545C). Costs of the two project elements were: Analysis = $12,045 and Restoration Maintenance and Enhancement = $44,018 for total of $56,063.

This project supported the ongoing monitoring for the Asotin IMW and to increase the wood density in existing treatment areas and promoted increased channel complexity and floodplain connection