An expert panel process to evaluate habitat restoration actions in the Columbia River estuary

We describe a process for evaluating proposed ecosystem restoration projects intended to improve survival of juvenile salmon in the Columbia River estuary (CRE). Changes in the Columbia River basin (northwestern USA), including hydropower development, have contributed to the listing of 13 salmon stocks as endangered or threatened under the U.S. Endangered Species Act. Habitat restoration in the CRE, from Bonneville Dam to the ocean, is part of a basin-wide, legally mandated effort to mitigate federal hydropower impacts on salmon survival. An Expert Regional Technical Group (ERTG) was established in 2009 to improve and implement a process for assessing and assigning "survival benefit units" (SBUs) to restoration actions. The SBU concept assumes site-specific restoration projects will increase juvenile salmon survival during migration through the 234 km CRE. Assigned SBUs are used to inform selection of restoration projects and gauge mitigation progress. The ERTG standardized the SBU assessment process to improve its scientific integrity, repeatability, and transparency. In lieu of experimental data to quantify the survival benefits of individual restoration actions, the ERTG adopted a conceptual model composed of three assessment criteria-certainty of success, fish opportunity improvements, and habitat capacity improvements-to evaluate restoration projects. Based on these criteria, an algorithm assigned SBUs by integrating potential fish density as an indicator of salmon performance. Between 2009 and 2014, the ERTG assessed SBUs for 55 proposed projects involving a total of 181 restoration actions located across 8 of 9 reaches of the CRE, largely relying on information provided in a project template based on the conceptual model, presentations, discussions with project sponsors, and site visits. Most projects restored tidal inundation to emergent wetlands, improved riparian function, and removed invasive vegetation. The scientific relationship of geomorphic and salmonid responses to restoration actions remains the foremost concern. Although not designed to establish a broad strategy for estuary restoration, the scoring process has adaptively influenced the types, designs, and locations of restoration proposals. The ERTG process may be a useful model for others who have unique ecosystem restoration goals and share some of our common challenges.