Puget Sound marine shorelines provide Pacific salmon habitat for migration, juvenile rearing, feeding, and refuge. These shorelines are also used as the primary spawning habitat for Pacific sand lance and surf smelt, two forage fish species that are eaten by many higher level predators including Chinook salmon. Marine nearshore degradation from armoring (bulkheads, sea walls, etc.) and concurrent vegetation loss have detrimental impacts on the survival of salmon. Since the listing of wild Puget Sound Chinook salmon as threatened under the Endangered Species Act in 1999, local efforts have been made in the Puget Sound to improve salmon habitats and recover populations. The 2005 Salmon Habitat Plan adopted by jurisdictions within the Green River Watershed in Western Washington has a primary goal to reduce the amount of shoreline armoring and intertidal fill.
To evaluate the progress of implementation, we examined changes to the shoreline since the plan was adopted. This study addresses two questions: What was the extent of intertidal fill associated with shoreline armoring when the Salmon Habitat Plan was initiated in 2005, and how has that changed in the ten years since the plan was adopted? The Puget Sound shoreline stretches 92 miles in the Green River Watershed and is roughly equally split between rural and urban areas. Shorelines were mapped using aerial imagery. The extent and area of intertidal fill changes were compared between 2005 and 2015 to evaluate progress of reducing intertidal fill in 10 years.
Results/Conclusions
Armored shorelines account for 68% of the shoreline in the Green River Watershed. Results indicate that the linear extent of shoreline armoring decreased by 0.2%. However, there is an associated loss of approximately 8,000 m2 of intertidal habitat since 2005. The majority of these intertidal area losses were attributed to expansions of existing armored shorelines associated with repairs and rebuilds. While these results indicate little change has been made to increase or improve intertidal habitats, shoreline development appears to have been limited during a time of significant population and urban growth. This simple analysis method of quantifying shoreline conditions is a useful tool that provides critical information for tracking plan implementation progress and developing adaptive management plans, and it can be applied in other watersheds and regions.