Pacific salmon (Onchorhynchus spp.) are considered a keystone species with great ecological, cultural and economic significance throughout the Pacific Northwest (PNW). However, generations of freshwater habitat degradation have resulted in the widespread decline of Pacific salmon. Pacific salmon have been eliminated from 40% of their historical range in the PNW and many remaining populations are either endangered or threatened. As a result, an average of >$90 million is spent annually on freshwater habitat restoration across the Pacific Northwest, California and Alaska.

One of the most popular forms of salmon habitat restoration is the construction of engineered log jams, which are often designed to create wood-formed pools through scouring processes. Such pools provide essential habitat for salmon, providing cover and a place to rest and conserve energy. In addition, deep pools provide critical cold-water refuge in the summer, when heat stress can result in mortality. Deep pool habitat will only become more critical with climate change, as summer stream temperatures in the PNW creep above the thermal tolerance of juvenile salmon. The goal of this research is to determine if engineered log jams are an effective restoration method for improving the ability of salmon populations to persist in climate-impacted rivers.

This research is being carried out in two phases. Phase one, which is nearly complete, looks at the extent to which engineered log jams result in physical improvements to freshwater habitat in the form of increased depth and frequency of pools. Phase two looks at whether juvenile salmon are responding to any changes in habitat from the engineered log jams. This research uses advanced statistical analyses of long-term monitoring data from 26 engineered log jam restoration sites throughout Washington State. The results will provide managers and policy-makers with accessible, decision-relevant science to guide climate adaptation actions for at-risk salmon populations.