Study shows new risks of flooding after Cascadia quake
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Land along parts of the Oregon coast could sink nearly 7 feet in the event of a major Cascadia Subduction Zone earthquake, significantly increasing long-term flood risks in some of the state's most popular beachside communities, according to new research.
Why it matters: The areas expected to be hardest hit by subsidence — including locations in Washington and Northern California — are home to tens of thousands of people, five airports and more than a dozen critical facilities like hospitals, schools and fire stations.
- In Oregon, that includes population centers along estuaries in places like Seaside, Astoria and Newport.
What they're saying: Significant sinking would complicate and delay rescue and recovery efforts in the immediate aftermath of the large quake, but in the long term, it "could render many coastal communities uninhabitable," the authors of the study wrote.
State of play: Tina Dura, professor of geosciences at Virginia Tech and lead author of the study, looked at how a quake would impact the coast now and in 2100, when rising sea levels will make flooding worse.
- Dura and her team generated thousands of earthquake simulations to determine how much land would sink and fall under the federal designation of "1% floodplain," meaning an area with a 1-in-100 chance of flooding each year.
By the numbers: The area that would be subject to those kinds of floods would more than triple after a major quake, Dura found, from 35 square miles to roughly 116, between Humboldt Bay in California and Grays Harbor in Washington.
- That would put more than 14,000 residents, 22,500 structures and 777 miles of roadway into a post-earthquake floodplain if it happened today.
- By 2100 — when experts predict sea levels could rise by 1 to 3 feet, due in part to climate change — a major quake could convert an additional 145 square miles into floodplain.
- That scenario would put another 17,000 residents, nearly 30,000 structures and around 1,000 miles of roads in a floodplain zone.
Threat level: Harold Tobin, director of the Pacific Northwest Seismic Network and a professor at the University of Washington, told NBC News this kind of "permanent change to land level at the coast" should change how communities plan for the future.
- "Where are you going to put your school or hospital? Where are you going to build your transportation network? I think it's important to take the long view," he said.
What's next: But the near term is important, too, Dura told Axios, stressing the importance of updating evacuation plans, retrofitting key pieces of infrastructure and preserving natural buffers.
- "Awareness and proactive planning today can greatly reduce the long-term consequences of a major earthquake," Dura said.