Coronado's low-lying shoreline faces heightened coastal flooding risk this winter as a massive El Niño-driven wave pushes sea levels up to a foot higher along the California coast.
The surge, called a Kelvin wave, has already raised water levels nine to 14 inches along the Central American coast, the San Francisco Chronicle reported. The wave is traveling north at about 6 mph and is expected to reach Cabo San Lucas in late September before arriving in Southern California by early October.
Water levels along the San Diego coast already sit well above normal.
"So far this summer, what we've been seeing is that the actual water levels have been running about six inches above what the predicted water levels have been," Stefanie Sullivan, lead meteorologist at the National Weather Service San Diego, told CBS 8 on Wednesday, Sept. 2.
Sullivan warned that the elevated baseline raises the potential for coastal flooding around King Tides and high-surf events, naming Mission Beach and Oceanside as areas already prone to flooding. Those events could become more frequent or push further inland than usual, she said.
Coronado sits in a coastal zone surrounded by water on nearly all sides, making it vulnerable to storm surf, heavy rain and King Tides, according to a Times of San Diego opinion column published Saturday, Aug. 29. Residents saw that vulnerability in January 2024, when heavy rains and high tides caused record flooding. A pump station in the Country Club area failed, knocking out the city's ability to pump floodwaters and provide sewer service in that neighborhood, the column reported.
Coronado has since invested tens of millions of dollars in sewer and stormwater improvements citywide, according to the column.
California's highest King Tides are predicted on Thanksgiving Day, Nov. 26, and Christmas Day, Dec. 25, with another round in late January 2027. Water levels could rival the highest in recorded history even without a nearby storm, the Chronicle reported.
NOAA's Climate Prediction Center puts the chance of a "super" El Niño at 95%, with roughly a 7-in-10 chance it will be the strongest such pattern since 1950, the Los Angeles Times reported on Aug. 13. The pattern also coincides with the peak of an 18-year astronomical cycle that pushes high tides even higher, according to Patrick Barnard, research director at the Center for Coastal Climate Resilience at UC Santa Cruz.
Barnard told CNN that the six-inch to one-foot increase in coastal water levels could threaten an additional 170,000 people and $60 billion in property statewide compared to a year without a super El Niño. Pacific storms also generate about 30% more wave energy during an El Niño year, Barnard told CNN.
September and October tides are among the lowest of the year, so the Kelvin wave is not expected to cause immediate coastal flooding, the Chronicle reported. But the elevated water levels set the stage for a stretch from late November through January when King Tides and storm surf could combine with the higher baseline.
Coronado City Councilmember Amy Steward, writing in the Aug. 29 Times of San Diego column, said the city is aware of the threat. "We must remain vigilant and plan for the future," Steward wrote.
Residents can sign up for emergency alerts through the County of San Diego's AlertSanDiego notification system and monitor conditions through the National Weather Service San Diego office.
