Long-Term Effects of a Large Wood Placement Project on Wood Abundance and Salmonid Smolt Populations in an Oregon Coastal Stream

Long-term effectiveness monitoring of large wood placement projects is rare despite the widespread use of this restoration technique. Tenmile Creek on the central Oregon coast was the subject of an extensive wood placement project in 1996, with a significant natural wood recruitment event occurring the same year. A basin-scale effectiveness monitoring program was implemented for five years before and after the treatment to evaluate effects on salmonid populations, and annual smolt monitoring has continued through the present. The wood addition in 1996 initially increased wood volume in Tenmile Creek to levels observed in a nearby reference stream, but a full-basin survey in 2013 indicated that wood abundance has dropped throughout Tenmile Creek since then. Wood volume and the number of key pieces remain higher than before the treatment in some reaches, but have fallen below pre-treatment levels in others. The wood addition increased juvenile salmonid freshwater survival in the short term, and appears to have had long-term positive effects on steelhead smolt abundance when Tenmile Creek is compared to an adjacent reference stream. Our results indicate that the wood placement project had short- and long-term benefits for salmonid populations, but also underscore the importance of maintaining natural wood recruitment processes.