Maximizing ecological and social benefits of habitat restoration in the Lower Duwamish River: A spatial framework for site selection

Abstract

The Lower Duwamish River (LDR) estuary is an 11-mile stretch of river that contains the core of industrial activity in the Seattle area. As the city's only river, the LDR also provides important habitat for many of the region's valued fish and wildlife species. However, its long history of urban development and industrial activity has polluted and degraded the river, and significant habitat restoration is now required under federal and state law. Given the highly developed urban industrial setting of the LDR, habitat restoration projects tend to be small and opportunistic, with limited ecological value. At the same time, the LDR is home to several underserved urban neighborhoods, and restoration projects have the potential to bring significant social value to these communities. Maximizing this potential value together with ecological value requires a more strategic approach to restoration. Through a review of local and regional planning documents, I developed a list of community-defined characteristics that contribute to a restoration project's potential ecological and social value in the LDR. I then used these characteristics to explore the spatial distribution of potential restoration value in the river, creating a series of heat maps of potential value for each characteristic, and for overall potential ecological and social value. I developed six ecological metrics and eight social metrics, which I calculated for 511 waterfront parcels in the LDR. Results show more variability with positive skewness in the ecological index, and a more normal distribution with higher average values in the social index. Spatial analysis revealed higher ecological value in the northern, industrial section of the LDR, with particular dependence on the existing habitat network. Social value was higher in the southern section and as the river passes through residential neighborhoods. These results can inform site selection for future restoration projects in the LDR. Methodologies and results for individual metrics can be used to address project-specific objectives, while use of the complete collection can inform those restoration projects that seek to maximize overall ecological and social benefits in the LDR.