Six locations along California's coastline are at an increased risk of flooding and erosion due to a combination of rising sea levels and a potentially powerful El Niño, according to a new study by UC Davis. The affected areas include parts of San Luis Obispo, Monterey and Santa Cruz, the South San Francisco Bay, Marin's North Bay corridors, Stinson Beach, and Humboldt Bay.

The study, released by the UC Davis Road Ecology Center, highlights that these hotspots could experience beach loss, damage to shoreline properties, unstable bluffs, and destruction of infrastructure. The enhanced risk is attributed to a foot of sea-level rise, a consequence of climate change, compounded by the potential for one of the strongest El Niño events on record.

Specific areas of concern include:

  • San Luis Obispo County: Public beaches and roadways in Avila Beach and Pismo Beach are vulnerable to significant erosion and wave damage.
  • Monterey & Santa Cruz Coastline: The Elkhorn Slough area, Moss Landing, local roads, agricultural lands, and coastal housing in Santa Cruz face a high risk of inundation.
  • South San Francisco Bay: Residential areas, local roads, marshes, and key transportation infrastructure, including San Francisco International Airport, East Bay marshes, and portions of I-80 near the Bay Bridge, are at elevated flood risk.
  • Marin & North Bay Arterials: Critical routes like U.S. 101 in Corte Madera, residential areas in San Rafael, and segments of Highway 37 near Novato Creek, Petaluma River, and Mare Island are susceptible to saltwater flooding.
  • Stinson Beach: Oceanfront homes, local roads, and beach infrastructure are directly threatened by storm surge and coastal erosion.
  • Humboldt Bay: Surrounding agricultural fields, local roadways, U.S. 101 corridors, and low-lying marshes are highly vulnerable due to the combined effects of high tides and runoff.

Fraser M. Shilling, Director of the Road Ecology Center at UC Davis, stated that the current issues were predicted years ago and should not come as a surprise. He noted that an "eastern Pacific Kelvin wave" coupled with storm tracks pushing water inland has already led to significant surf and flooding along the Southern California coast. Shilling also expressed concern that some coastal areas, like Long Beach and Newport Peninsula, might suffer irreversible damage to their beaches, beyond the scope of traditional solutions like riprap and sand augmentation.

Researchers emphasize that the confluence of elevated sea levels and severe weather events, such as heavy swells and inland runoff, will lead to widespread flooding and accelerated erosion across the state. The study recalls the winter of 2019, when atmospheric river storms raised coastal waters by nearly 10 inches, causing a shutdown of Highway 37 in the North Bay even during a weaker El Niño event.