Increased flood exposure in the Pacific Northwest following earthquake-driven subsidence and sea-level rise.

Authors

Tina Dura, William Chilton, David Small, Andra J Garner, Andrea Hawkes, Diego Melgar, Simon E Engelhart, Lydia M Staisch, Robert C Witter, Alan R Nelson, Harvey M Kelsey, Jonathan C Allan, David Bruce, Jessica DePaolis, Michael Priddy, Richard W Briggs, Robert Weiss, SeanPaul La Selle, Michael Willis, Benjamin P Horton

Published in

Proceedings of the National Academy of Sciences of the United States of America. Volume 122. Issue 18. Pages e2424659122. May 06, 2025. Epub Apr 28, 2025.

Abstract

Climate-driven sea-level rise is increasing the frequency of coastal flooding worldwide, exacerbated locally by factors like land subsidence from groundwater and resource extraction. However, a process rarely considered in future sea-level rise scenarios is sudden (over minutes) land subsidence associated with great (>M8) earthquakes, which can exceed 1 m. Along the Washington, Oregon, and northern California coasts, the next great Cascadia subduction zone earthquake could cause up to 2 m of sudden coastal subsidence, dramatically raising sea level, expanding floodplains, and increasing the flood risk to local communities. Here, we quantify the potential expansion of the 1% floodplain (i.e., the area with an annual flood risk of 1%) under low (~0.5 m), medium (~1 m), and high (~2 m) earthquake-driven subsidence scenarios at 24 Cascadia estuaries. If a great earthquake occurred today, floodplains could expand by 90 km² (low), 160 km² (medium), or 300 km² (high subsidence), more than doubling the flooding exposure of residents, structures, and roads under the high subsidence scenario. By 2100, when climate-driven sea-level rise will compound the hazard, a great earthquake could expand floodplains by 170 km² (low), 240 km² (medium), or 370 km² (high subsidence), more than tripling the flooding exposure of residents, structures, and roads under the high subsidence scenario compared to the 2023 floodplain. Our findings can support decision-makers and coastal communities along the Cascadia subduction zone as they prepare for compound hazards from the earthquake cycle and climate-driven sea-level rise and provide critical insights for tectonically active coastlines globally.

PMID:
40294262
Bibliographic data and abstract were imported from PubMed on 29 Apr 2025.

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