DISASTERSFlood Risk Increasing in Pacific Northwest
The next great earthquake isn’t the only threat to the Pacific Northwest. A powerful earthquake, combined with rising sea levels, could significantly increase flood risks in the Pacific Northwest, impacting thousands of residents and properties in northern California, Oregon, and Washington.
The next great earthquake isn’t the only threat to the Pacific Northwest.
A powerful earthquake, combined with rising sea levels, could significantly increase flood risks in the Pacific Northwest, impacting thousands of residents and properties in northern California, Oregon, and Washington, according to new Virginia Tech research.
A study published this week in the Proceedings of the National Academy of Sciences found that a major earthquake could cause coastal land to sink up to 6.5 feet, expanding the federally designated 1 percent coastal floodplain, an area with a 1-in-100 chance of flooding each year, by 35 to 116 square miles.
“The expansion of the coastal floodplain following a Cascadia subduction zone earthquake has not been previously quantified, and the impacts to land use could significantly increase the timeline to recovery,” said researcher Tina Dura, lead author of the study and assistant professor of geosciences in the College of Science.
The research shows the most severe effects would hit southern Washington, northern Oregon, and northern California, densely populated areas in the region.
Dura’s team generated tens of thousands of earthquake models to estimate the potential range of earthquake-driven subsidence, or sinking land, that can be expected from the next large Cascadia earthquake. Then, using geospatial analysis, the team quantified the earthquake-driven expansion of the 1 percent floodplain at 24 estuaries and communities along the Cascadia subduction zone. Because the timing of the next large earthquake is uncertain, the team modeled the impacts of an earthquake striking today or in 2100, when climate-driven sea-level rise will further amplify the impacts of earthquake-driven subsidence.
The study estimates that following an earthquake today, an additional 14,350 residents, 22,500 structures, and 777 miles of roadway would fall within the post-earthquake floodplain, more than doubling flood exposure. Potential flooding would affect five airports; 18 critical facilities, including public schools, hospitals, police stations, and fire stations; eight wastewater treatment plants; one electric substation; and 57 potential contaminant sources, including animal feeding operations, gas stations, and solid waste facilities.
By 2100, the Intergovernmental Panel on Climate Change localized relative sea-level rise projections show that sea levels along the Cascadia subduction zone could be up to 3 feet higher than today. This climate-driven sea-level rise will amplify the impacts of future earthquake-driven subsidence, more than tripling the flood exposure of residents, structures, and roads.
