Nisqually 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 Nisqually Delta in the South Sound sub-basin historically contained 2,502 acres of vegetated wetland along a 20 km shoreline. The delta receives flow from a 214,377 square kilometer watershed. These characteristics make this system the 5th largest delta out of 16 systems in Puget Sound.
Simenstad et al 2011 found that this system had lost 77% of its vegetated tidal wetlands, and 68% of its shoreline length. Of the remaining shoreline, 73% shows some evidence of infrastructure development. In the surrounding uplands, 17% of land is estimated to have greater than 10% impervious surface. Across the watershed, 25% of land is estimated to have greater than 10% impervious surface. Based on these paramters, the site was given a degradation score of 52 out of 100, making it the 5th most degraded delta in Puget Sound. It faces a medium risk of future development locally, and a medium risk of development across the watershed. Approximately 44% of the watershed is currently impounded behind dams.

Restoration Efforts and Issues

  • The Nisqually Refuge Restoration and Red Salmon Slough Restoration have largely restored historical tidal flow in the Nisqually Delta.
  • While these projects removed river levee, The Nisqually Refuge dike and I-5 causeway constrain how freshwater, fish and sediment enter the delta.
  • The Alder Dam impounds river sediment from a portion of the Nisqually basin, limiting sediment that reaches the delta.




Nisqually River Delta Sediment Budget and Assessment of Opportunities to Recover Sediment Supply to Sustain Marsh

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