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Dr. Tina Dura, professor at Virginia Tech and an expert in coastal hazards, explains in the latest Risky Science Podcast how a major earthquake along the Cascadia Subduction Zone could permanently reshape the Pacific Northwest's floodplain, with long-lasting physical and economic consequences.
Her recent work focuses on how the next mega thrust earthquake will alter the floodplains along the coast based on field research that reconstructs seismic history from sediment records. “We come up with numbers between a meter or two meters in extreme cases that the land dropped down during the earthquake," Dura explains.
That sudden subsidence, which “happens over minutes,” would move roads, homes, ports, and wastewater facilities into the 1% annual floodplain nearly instantly. “If you suddenly lower those estuaries by two meters, you will convert a lot of these low-lying areas into floodplain,” she says.
The earthquake risk is compounded by accelerating sea level rise.
By 2100, a meter of sea level rise, climate-driven sea level rise, is perfectly within what we could see. And then we get an earthquake in 2100 on top of that... you have an even larger expansion of that floodplain.
The result? A sharp increase in the number of people, buildings, and critical infrastructure at risk. “We have airports, emergency response facilities, hospitals, there’s schools that are in the post-earthquake floodplain.”
Despite this threat, Dura notes the current system of FEMA flood maps does not account for post-earthquake land-level change and describes her teams research process could model a better view of the risk.
We provided maps and GIS shapefiles that could basically be overlaying on the existing FEMA flood maps that could depict a new boundary, a new post-earthquake boundary for the one percent floodplain.
But integrating this science into planning and insurance frameworks remains a challenge, especially in the US and in the Cascadia region that has not experienced a significant event in over a century.
I fear that... because we don’t have these reminders like they have in Chile or even in Japan... it’s going to have a lot larger effect in the Pacific Northwest.
🛰️ Listen to the full episode here
Show Notes
🧑🔬 Guest
Tina Dura, College of Science, Department of Geosciences
Increased flood exposure in the Pacific Northwest following earthquake- driven subsidence and sea- level rise, Proceedings of the National Academy of Sciences (PNAS)
🌊 Background
Cascadia Region Earthquake Science Center
Cascadia Subduction Zone, Pacific Northwest Seismic Network
Economic Analysis of a Cascadia Subduction Zone Earthquake, ECONorthwest
