San Diego coastal treasures and El Niño
Cliff collapse and erosion aren’t the only dangers posed by heavy rainfall and rising sea levels. Times of San Diego takes a look at what the experts are saying about El Niño's possible impact on coastal icons from San Onofre to the border.
Intro | North County | La Jolla | City beaches | Bayfront and South Bay
San Diego Bay
The 2015–16 El Niño provided a useful preview for how San Diego Bay will be affected by rising sea levels. The waterfront area is sheltered from large waves and erosion, but flooding is a major concern because of its direct connection to the Pacific.
The U.S. Geological Survey recorded water levels in 13 Southern California estuaries, comparing intermittently closed lagoons – which trap water inland and cause floods – and systems that are open year-round, such as San Diego Bay.
Researchers found the water level in open systems mirrored elevated ocean levels. This winter, the sea level may rise up to 13 inches temporarily, according to Scripps coastal geologist Adam Young.
San Diego’s Coastal Resilience Master Plan identifies sea-level-rise-driven flooding as a major threat to the city’s coastline, and there are long-term concerns about permanently increased sea levels caused by climate change. The city estimates that San Diego could see another 3.6 to 7 feet of sea-level rise by 2100.
Coronado
Coronado’s large beaches provide the biggest sand buffer in all of San Diego County, measuring in over 680 feet at its widest point, according to The Coronado Times in 2023. And yet, this large gap can close quickly during major storms.
Adam Young’s research team reported that the Silver Strand’s earth wall was overrun during the 2015-2016 El Niño. Adding to that, the Strand lost an average of roughly 3.8 feet of beach width per year over a 22-year study window, totaling an 81-foot reduction, according to SANDAG’s 2023 State of the Coast report.
The shifting shoreline is particularly visible at the Hotel del Coronado, which sits directly on the shrinking beach, as the waterline creeps ever closer to one of San Diego’s most recognizable coastal landmarks.
The beach remains an important natural defense, but its resilience depends on how much sand remains in the system. As Serge Dedina, a former Imperial Beach mayor and SANDAG board member, told Times of San Diego, “Ultimately much will depend on the ferocity of storms that combine large surf, big tides, strong winds and heavy rainfall to see how it all plays out.”
Imperial Beach
“Big El Niño-related winter storms have historically slammed these neighboring cities on the south and north ends of the Silver Strand,” Dedina wrote in an August opinion piece published by Times of San Diego. Beyond beach erosion and coastal flooding, El Niño can also worsen the Tijuana River sewage crisis — potentially sending more polluted water into the ocean as powerful waves reshape the coastline.
Nearshore currents generally flow south-to-north, which can carry polluted water from the Tijuana River Estuary up to Imperial Beach, Coronado and other beaches on San Diego’s coast. Stopping the water from flowing into the Pacific presents other problems.
Sand accumulated at the Tijuana River mouth during the 2015-16 El Niño, temporarily restricting the estuary’s outlet into the ocean. The resulting conditions contributed to the deaths of leopard sharks and other wildlife, according to the Los Angeles Times — which featured Dedina counting 50 dead sharks along the riverbank.
“While Coronado and Imperial Beach have embraced the need to upgrade their infrastructure to reduce the impacts of coastal flooding, they are both at the mercy of flooding from Tijuana,” Dedina wrote.
That makes Imperial Beach different from most of the county’s other coastal communities. Here, an El Niño storm can simultaneously reshape the shoreline and interfere with the river’s connection to the ocean — compounding the county’s coastal erosion problem with heavily polluted coastal flooding.
