Visualizing sea level rise on the Duwamish River

The King County Department of Natural Resources & Parks oversees several ecological restoration sites along the Duwamish River. Because the river is estuarine and will be impacted by the rising ocean levels associated with climate change, there was understandably some concern that these sites would also be affected. They needed to visualize what their projects would look like as the oceans rise.

To meet their need, we in the King County GIS Center Spatial Services group assembled a digital 3D model of the lower Duwamish River using 2019 lidar-derived elevation data. We then draped a high-resolution aerial image onto this model, and added simple 3D massings of the structures in the area. Finally, we calculated a 2-foot sea level rise from 2019 levels based on the high-resolution lidar data.*

The effects of just 2 feet of sea level rise along the Duwamish River are significant. Harbor Island and surrounding Port of Seattle lands, natural areas around Kellogg Island, and the industrial areas of Georgetown and South Park become inundated. Take a look at the results in the video below.

The Duwamish River with 2 feet of Sea Level Rise

*The 2-foot amount falls into the “Likely Range” by 2100 based on this 2018 study. The King County 2019 Digital Ground Model was the base elevation data. The sea level for this visualization was based on mean higher high water (DGM + 9 feet), with an added 100-year flood event of 3 feet.

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