Study warns of significant Pacific Northwest floods from earthquakes and sea-level rise

​The combination of tectonic activity and climate change could significantly increase flood risks in the region, according to a study published in the Proceedings of the National Academy of Sciences (PNAS).

Researchers have found that gradual sinking from a major earthquake along the Cascadia Subduction Zone, coupled with rising sea levels, could lead to substantial flooding in coastal areas.

“The next Cascadia earthquake will happen—it’s a matter of when, not if,” Dr. Tina Dura, lead author of the study and assistant professor of geosciences at Virginia Tech, said.​

Study Findings: We’re in for a flood?

The study reviews the potential impacts of a magnitude 9.0 earthquake, similar to the one that struck the region in 1700. Such an earthquake could cause the land to sink by up to six feet in some areas, exacerbating the effects of sea-level rise.​

“Earthquakes lower the land for decades to centuries after an earthquake. If a Cascadia earthquake happened today, coastal land from Washington to California could drop by 0.76–8.76 ft (0.23–2.67 m). This expands floodplains, leaving communities more exposed,” Dr. Dura explained.

She also noted that climate change is a contributing factor, even if there’s not a major earthquake.

“Climate change compounds the problem. Even if no earthquake happens, sea levels are rising—projected to rise 1.3-2.9 feet (0.4-0.9 meters) by 2100. This alone would expand coastal floodplains by 100 km² (40 mi²),” she said.

You can read the full study here.

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