Impacts of a Cascadia Subduction Zone Earthquake on Water Levels and Wetlands of the Lower Columbia River and Estuary

Journal Article · 12 July 2023 · Geophysical Research Letters

DOI: https://doi.org/10.1029/2023GL103017 · OSTI ID:1989511

Brand, M. W.  ^[1]; Diefenderfer, H. L.  ^[2]; O’Connor, J. E. ^[3]; Borde, A. B. ^[4]; Jay, D. A.  ^[5]; Al‐Bahadily, A. ^[6]; McKeon, M. ^[4]; Talke, S. A.  ^[7]

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1. Pacific Northwest National Laboratory Coastal Sciences Division Sequim WA USA, University of California, Irvine Irvine CA USA
2. Pacific Northwest National Laboratory Coastal Sciences Division Sequim WA USA, University of Washington Seattle WA USA
3. U.S. Geological Survey Portland OR USA
4. Pacific Northwest National Laboratory Coastal Sciences Division Sequim WA USA
5. Portland State University Portland OR USA
6. Mustansiriyah University Baghdad Iraq
7. California Polytechnic State University San Luis Obisbo CA USA

Abstract Subsidence after a subduction zone earthquake can cause major changes in estuarine bathymetry. Here, we quantify the impacts of earthquake‐induced subsidence on hydrodynamics and habitat distributions in a major system, the lower Columbia River Estuary, using a hydrodynamic and habitat model. Model results indicate that coseismic subsidence increases tidal range, with the smallest changes at the coast and a maximum increase of ∼10% in a region of topographic convergence. All modeled scenarios reduce intertidal habitat by 24%–25% and shifts ∼93% of estuarine wetlands to lower‐elevation habitat bands. Incorporating dynamic effects of tidal change from subsidence yields higher estimates of remaining habitat by multiples of 0–3.7, dependent on the habitat type. The persistent tidal change and chronic habitat disturbance after an earthquake poses strong challenges for estuarine management and wetland restoration planning, particularly when coupled with future sea‐level rise effects.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE; USGS
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1989511
• Report Number(s): PNNL-SA--181915; e2023GL103017
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Journal Issue: 14 Vol. 50; ISSN 0094-8276
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English