On Oct. 23, USD alumnus Charlie Jin received a phone call from a friend living near Mission Bay.
“Two Fridays ago my friend called me asking if he could park his car at my place,” Jin said. “His house had flooded and he didn’t want his car to get soaked in water.”
Over the last several weeks, El Niño conditions contributed to the formation and movement of Kelvin waves across the Pacific Ocean, temporarily raising baseline sea levels and increasing the San Diego coastline’s susceptibility to flooding and coastal erosion.
Katrina Cantu, USD professor of environmental and ocean sciences, explained the phenomenon and why it matters.
“During an El Niño, the normal trade winds that blow east to west slow down or even stop and reverse,” Cantu said. “Sea levels are typically higher in the Asia side of the Pacific compared to the Americas side of the Pacific because of that wind, but when the wind slows down, that water comes sloshing back down across the Pacific and raises sea levels. That’s what happened here a little less than a month ago … Our sea level rose about a foot pretty rapidly.”
Seasonal high tides tend to intensify coastal hazards, and as winter approaches, an extra foot of water can significantly raise the risk of flooding and erosion, according to Cantu.
“When you have a rapid change like that, it starts to impact areas that are not as well prepared,” Cantu said. “People who live in cliffside homes are going to be seeing their backyards disappear, their patios disappear … Houses and streets that don’t normally flood will now get floods.”
As sea levels continue to rise in San Diego, the connection between elevated water levels and coastal erosion has become more pronounced. However, San Diego already faced a high risk of coastline erosion before this event, according to Danny Tal, a USD senior studying environmental and ocean sciences.
“Coastal erosion refers to the degradation of rocks or other matter on the coast due to wind, wave movement, atmospheric deposition or human activities like construction or industrial activities,” Tal said. “As a coastal city which has high wave action and industrial activity, coastal erosion greatly affects the city, as well as putting beach homes at risk.”
According to the California Coastal Cliff Erosion Viewer, a tool developed by researchers at the Scripps Institution of Oceanography at University of California, San Diego, cliffs near Pacific Beach, La Jolla and Sunset Cliffs receded between 0.06 and 0.08 meters per year between the years of 1998 and 2023, running slightly above the statewide average of 0.06 meters.
While these numbers show that coastal erosion is not new for San Diego, temporary sea-level rise from El Niño conditions may intensify risks for more vulnerable San Diego communities. Areas from Pacific Beach to La Jolla face potential risks that extend beyond the shoreline, threatening nearby neighborhoods, homes and infrastructure.
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