The California Geological Survey (CGS), which is a branch of the California Department of Conservation, recently updated its Tsunami Hazards Maps that affect Marin, Sonoma, Napa, and Solano counties — showing an increased risk of inland flooding for each of them.
Since 1850, there have been around 50 or so credible tsunamis recorded or observed within the San Francisco Bay Area. The most severe tsunami wave to ever strike the Bay Area happened on April 1, 1946, when a magnitude-7.4-magnitude earthquake off Alaska started a massive tsunami that sent waves as high as 15 feet tall crashing into the coastlines around Half Moon Bay.
TODAY, the CA Tsunami Program (@Cal_OES, @CAGeoSurvey, NOAA) published updated Tsunami Hazard Area Maps for Marin, Napa, San Diego, Santa Cruz, Solano, Sonoma, & Ventura counties! Go to https://t.co/CTmiphYrUm to know if you're in a tsunami hazard area!@CalConservation #Tsunami pic.twitter.com/Mg0Mi3O7zo— California Geological Survey (@CAGeoSurvey) October 7, 2022
After the Hunga Tonga-Hunga Ha’apai volcano triggered a global tsunami warning in January of this year — the volcanic blast perhaps the most violent eruption ever captured by satellite — deep waves of displaced water began traveling toward the West Coast, including the Bay Area. Though the National Weather Service indicated that peak waves from the tsunami were around 2 feet, widespread flooding was observed across the Bay Area; it caused upwards of $10M in damages. The latter, most recent tsunami event in the region showed just how vulnerable we are to sudden ocean swells, as well as rising sea levels.
And for the first time since 2009, the CGS has updated its Tsunami Hazard Maps for the state, which included changes to seven counties.
In the updated maps published Friday, four of the seven countries that saw a refresh were located in the Bay Area: Marin, Sonoma, Napa, Solano, Santa Cruz, San Diego, and Ventura counties were all included in the update. (A quick scroll through the map directories shows Alameda, Santa Clara, San Mateo, and Contra Costa counties were all updated in 2021.)
Our goal is to ensure that coastal communities are aware of & prepared for the next tsunami. The updated Tsunami Hazard Area Maps can be used by officials, communities, & individuals/families to update or create their tsunami evacuation plans. 2/2@CalConservation #Tsunami pic.twitter.com/x6Esgs1Ie3— California Geological Survey (@CAGeoSurvey) October 7, 2022
According to the maps, a sizable tsunami could send seawater into parts of the Napa County Airport; flooding from a tsunami would affect many areas of the Petaluma Valley; Sausalito would be almost entirely consumed by a strong tsunami event — and the small town of Bolinas would suffer a similar fate.
As for us here in San Francisco, our city's steep hills and elevation spare us from absolute destruction. Per these Tsunami Hazard Maps, many of the neighborhoods East and North of Golden Gate Park will be spared from catastrophic flooding. However, areas of the city that sit closer to the sea — like the Embarcadero, Hunters Point, and parts of SoMa — could very well be swallowed by the ocean in the event that a large tsunami comes barreling our way.
You can check out the updated interactive tsunami hazard maps, below:
Photo: Courtesy of Getty Images/Lemaneih