Catastrophic earthquake may submerge significant portion of California, substantially increasing flood vulnerability, according to research findings.
In a catastrophic earthquake scenario along the Cascadia subduction zone, stretching from Northern California up to Canada's Vancouver Island, things could get pretty grim. The area at risk of flooding would skyrocket by a staggering 116 square miles, that's nearly 2.5 times the size of San Francisco.
This terrifying scenario could see popular California coastal cities like Eureka and Arcata in the Humboldt Bay region submerged. A megaquake would not just unleash a tsunami and violent shaking, but also trigger land subsidence that could last for decades or even centuries, dramatically altering shorelines and causing lasting impacts to coastal populations, infrastructure, and ecosystems. Unlike gradual climate-driven sea-level rise, a rise resulting from a major earthquake "will happen within minutes, leaving no time for adaptation or mitigation."
Unfortunately, many of the areas at greatest risk are already populated. More than 8,000 people currently live in flood-prone zones along the Cascadia coastal region, a number that could nearly triple to over 22,000 in the event of a high level of subsidence after an earthquake. Nearly 36,000 structures would be threatened by the resulting quake-influenced floodplain, a 168% increase from the current figure of about 13,000.
In addition, over 1,200 miles of roadway could find themselves in the new floodplain, nearly tripling the at-risk total.
The Federal Emergency Management Agency defines the floodplain as areas that have at least a 1% chance of flooding each year, which is considered "high risk." These are areas that have at least a 1-in-4 chance of flooding during a 30-year mortgage. Flood insurance must be purchased by home and business owners in high-risk areas with mortgages from federally regulated or insured lenders.
Planning for subsidence impacts should be a top priority, experts say. Officials should consider avoiding building infrastructure such as schools, fire stations, and wastewater treatment plants in areas likely to become the floodplain, Dura advises.
Notable areas at risk of land sinking after a megaquake along the Cascadia subduction zone include:
- California's Humboldt Bay region, including the area around Eureka and Arcata.
- Oregon’s Waldport and Bayshore along Alsea Bay; Newport and South Beach along Yaquina Bay; and Gearhart and Seaside along the Necanicum River.
- Washington's Willapa Bay area, including the communities of Long Beach, Ocean Park, Tokeland, and Raymond; and the Grays Harbor area, including Ocean Shores, Westport, and Aberdeen.
In other words, we'd better brace ourselves for some drastic changes along the Pacific Northwest coast. It's not a matter of if, but when, a megaquake strikes, and we'd best be prepared.
- The government must address the potential disaster that a Cascadia earthquake could cause, considering the growth of populated areas at risk along the coast of California, Oregon, and Washington.
- Environmental science and educational institutions could collaborate to research and develop strategies for mitigating the impacts of climate change, earthquakes, and oversalinization on the environment in the Pacific Northwest.
- Businesses in the region must assess their vulnerabilities to earthquakes, flooding, and long-term subsidence, adapting their operations and investing in earthquake-resistant infrastructure to maintain continuity.
- Health organizations and medical professionals should prepare for an influx of patients with various injuries and medical conditions caused by earthquakes, flooding, and subsequent weather anomalies.
- The government should support the development of resilient infrastructure, such as earthquake-resistant buildings and flood barriers, to protect cities like Los Angeles, which lies outside the direct Cascadia subduction zone but could still face significant damage from tsunamis or shake-induced flooding.
- Science and technology can play crucial roles in predicting earthquakes and developing early-warning systems, as well as in creating efficient evacuation routes and emergency response plans.
- The culture of the Pacific Northwest, deeply rooted in a connection to nature and outdoor activities, should adapt to include preparedness for disasters and a focus on sustainable lifestyles that minimize contributions to climate change.
- The science community must continue to monitor the Cascadia subduction zone for signs of increased seismic activity, alerting the general public and authorities to potential threats.
- Weather forecasting and preparedness organizations need to be ready to provide accurate information about the immediate risks posed by earthquakes, tsunamis, and storms following a megaquake, ensuring that residents can take appropriate actions.
- Environmental-science researchers should investigate the potential long-term effects of earthquakes on ecosystems, including changes to wildlife habitat, the proliferation of invasive species, and the impact on the region's unique biodiversity.
- Media outlets should cover the risks and updates regarding Cascadia earthquakes comprehensively, providing residents with accessible and reliable information about potential threats, emergency preparations, and resources for self-development and education on related topics.
- As the risk of earthquakes, flooding, and subsidence increases along the Cascadia coast, the finance industry should consider supporting disaster-relief efforts, as well as working with home and business owners to make loans available for earthquake-resistant projects.
- Recreational sports organizations should collaborate with safety experts to create guidelines and protocols for organizing safe events during and after an earthquake, ensuring the health and well-being of participants in sports like surfing, sailing, and fishing along the affected coastlines.
