Western Washington culvert prioritization indexes: A cross jurisdictional comparative analysis of management strategies for salmon recovery

Abstract

Culverts throughout western Washington state, U.S.A., contribute to declines in anadromous fish populations by blocking fish passage. A federal injunction requires that Washington state must restore 90 percent of blocked habitat caused by state-owned culverts by 2030. This ruling prompted the development of numerous prioritization indexes (PI), the ranking of barriers through weighted combinations of barrier-specific metrics, by culvert owning entities (i.e., counties, cities, ect.) within the injunction area. We conduct a comparative analysis of PIs within the injunction case area, investigating their ability to distinguish between barriers, their transferability in terms of scoring metrics utilized, how scoring weights differ, and the preferences implied thereby. We document the use of six distinct PI methods by ten barrier owning entities, and find that some PIs used many shared metrics, while others used a high percentage of unique metrics that would be difficult to replicate outside the entitys jurisdiction. While habitat quality, habitat quantity, and connectivity were considered across all PIs, we found a high level of variation in terms of the metric weights. Our methods can be employed in other geographies or for other restoration PI planning efforts, and our results may facilitate the development and refinement of future PIs.