Duwamish Delta

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Nearshore Strategies Data Report

Cereghino et al 2012 completed a soundwide analysis to identify and describe river delta sites in Puget Sounds as part of a nearshore ecosystem restoration strategy (using remote sensing data c. 2000-2006). The following narrative of this delta site was developed to support distribution and use of analysis results:

The Duwamish Delta in the South Central Sub-basin historically contained 1,532 acres of vegetated wetland along a 32 km shoreline. The delta receives flow from a 124,268 square kilometer watershed. These characteristics make this system the 9th largest delta out of 16 systems in Puget Sound.
Simenstad et al 2011 found that this system had lost 100% of its vegetated tidal wetlands, and 100% of its shoreline length. Of the remaining shoreline, 100% shows some evidence of infrastructure development. In the surrounding uplands, 100% of land is estimated to have greater than 10% impervious surface. Across the watershed, 100% of land is estimated to have greater than 10% impervious surface. Based on these paramters, the site was given a degradation score of 76 out of 100, making it the 1th most degraded delta in Puget Sound. It faces a medium risk of future development locally, and a high risk of development across the watershed. Approximately 52% of the watershed is currently impounded behind dams.


  • A population of restoration efforts have been completed under NRDA authorities.