Where El Niño may impact California coastal areas this winter
Driving across Highway 37 in the San Francisco Bay Area on the best of days already feels like driving on top of water. Buffeted on both sides by marshlands hosting egrets, herons, ducks and a handful of endangered species, the sea-level highway is a major connector linking Marin, Sonoma, Napa and Solano counties.
The University of California, Davis has released a report warning of potential coastal flooding in California this winter due to an upcoming El Niño event. Highway 37, a key connector between Marin, Sonoma, Napa, and Solano counties, is particularly vulnerable to flooding and failure during this winter season. The report's author, Fraser Shilling, director of the UC Davis Road Ecology Center, stated that the risk of catastrophic flooding in various coastal towns is present, though not certain.
Shilling compared the current situation to one predicted 10 years ago, noting that the problems along Highway 37 and other coastal roads have not been addressed. In Long Beach and Newport Beach, an El Niño-induced Kelvin wave combined with a high tide and wave action caused sea level rise of 2 to 3 feet, damaging coastal properties and environments. Using the Surging Seas—Risk Zone Map, Shilling visualized the potential impact of similar sea level rise in California, revealing high-risk areas.
At 2 feet of sea level rise, airports and lowland beaches at the Bay Bridge begin to flood, while at 2 to 3 feet, international airports in San Francisco and Oakland, along with parts of San Rafael and West Oakland, start to flood. The most concerning areas are along Highway 37, which has stretches protected and unprotected by local levees.
A levee blowout along the Petaluma River could close Highway 37, leaving a 6-square-mile area up to 3 feet underwater. Major flooding or levee failures could also cause closures lasting months, affecting about 40,000 daily commuters and resulting in potential economic losses exceeding $1.5 million per day.
El Niño-related flooding also threatens endangered species such as the salt marsh harvest mouse and Ridgway's rail, which rely on Bay Area marshes for survival. Shilling emphasized that this winter could be the most catastrophic in recent history, urging for significant state and federal government response to prevent further catastrophes.
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