Description
King County has significant infrastructure in the former floodplain of the lower Duwamish River Valley. Sea level rise and projected increases in rainfall are likely to lead to a higher groundwater table in the Valley, putting this infrastructure at risk of groundwater inundation. The ability to accurately assess groundwater inundation risks to County infrastructure is insufficient, however, due to key knowledge gaps regarding how much and how quickly groundwater levels are impacted by tidal events, river flows, and intense rainfall.
King County will continue to partner with U.S. Geological Survey and the King County International Airport to evaluate how groundwater levels in the lower Duwamish River Valley respond to sea level rise, flooding, and tidal fluctuations. The phased study, started in 2024, will improve understanding of how much groundwater levels in the Valley are impacted by tidal events, river flows, and intense rainfall. The work will create a groundwater framework of existing conditions, laying the foundation for additional work that studies projected changes in groundwater levels and groundwater inundation risk assessments for King County infrastructure in the Duwamish Valley.