San Diego Braces for a Winter of Floods, High Surf and El Niño Extremes

San Diego officials are bracing for a winter of weather whiplash as a powerful El Niño takes hold, with forecasters warning the region could see anything from destructive flash floods to punishing surf — or, just as easily, a disappointingly dry season with elevated wildfire danger.

The climate pattern, driven by warmer-than-normal waters in the tropical Pacific and weakened trade winds, has historically ushered in wet winters for Southern California. But its track record is inconsistent enough that emergency planners are hedging their bets rather than betting on a single outcome.

“Large El Niños tend to tilt the odds toward more winter storms moving through the north Pacific, and bigger ones too, because of the extra energy the ocean feeds into the atmosphere,” said Dan Cayan, a climate researcher at Scripps Institution of Oceanography.

Still, the relationship between ocean warming and actual rainfall has grown less reliable in recent decades, complicating forecasts and pushing local governments to prepare for a broad spectrum of possibilities. Compounding the uncertainty is San Diego’s stormwater infrastructure, much of it decades old, along with a fleet of century-old dams that need major repairs.

In response, the city of San Diego has assembled an El Niño task force pulling in representatives from every municipal department to coordinate emergency response.

“From San Ysidro up through Sorrento Valley and Lake Hodges — anywhere there’s a creek, river or lake — we have to watch those spots closely to make sure we’re ready if extreme weather hits,” said Assistant Fire Chief Robert Rezende, who is overseeing the effort.

A pattern with a mixed history

El Niño takes shape when sea surface temperatures rise in the central and eastern tropical Pacific. The trade winds that typically blow from the Americas toward Asia slacken, sometimes even reversing course toward the California coast. That shift pushes warm water eastward, causing air to rise and spawning storm activity.

Meteorologists classify an El Niño once ocean temperatures climb a half-degree Celsius above average, according to Tyler Rodenbaugh, senior meteorologist for the San Diego County Water Authority. A reading of 1.5 degrees above normal earns the label “very strong” — which is where conditions stand today.

History shows these events can bring dramatically more rain. During the El Niño winters of 1982-83 and 1997-98, San Diego logged about 70 rainy days compared with the usual 40 to 45, and nearly 20 inches of rain fell at Lindbergh Field, roughly double a typical year’s total. Statewide, Sierra Nevada snowpack swelled as well, adding to runoff.

Yet the so-called “Godzilla El Niño” of 2015-16 broke that pattern entirely, delivering just 8 inches of rain at Lindbergh Field — well below normal.

“What actually happens depends on individual storms known as atmospheric rivers, and those don’t necessarily follow El Niño’s lead,” said Alexander Gershunov, a research meteorologist at Scripps.

Atmospheric rivers are narrow bands of concentrated moisture — essentially rivers flowing through the sky — that ferry water vapor from the tropics and can trigger intense downpours, according to the National Oceanic and Atmospheric Administration.

Flood risk on the ground

San Diego’s terrain — hillside developments, floodplain construction and a maze of canyons — makes it especially prone to flooding when storms do arrive. How much damage results often comes down to whether the region’s flood-control systems can keep pace.

The January 2024 flooding along Chollas Creek offered a stark example, damaging roughly 1,000 homes in the Shelltown neighborhood of southeastern San Diego.

Rezende described it as a “1,000-year flood” that couldn’t have been avoided, and Cayan noted the creek’s small watershed is especially vulnerable to sudden, intense rain bursts. But many residents believe the destruction was made worse by years of deferred maintenance. Thousands filed lawsuits alleging the city failed to properly maintain its storm channels, worsening the flooding. Survivors say they continue to grapple with health issues — rashes, respiratory trouble, swelling — that they link to floodwater exposure and subsequent mold contamination in their homes.

The city’s current budget touts more than $800 million already spent on stormwater upgrades, including 18 projects finished last year, but acknowledges another $3.3 billion in needed work without a clear funding plan. City officials did not respond to requests from CalMatters for additional details on stormwater spending.

Still, officials say they’re keeping up routine maintenance where they can. The Stormwater Department is clearing debris from channels to keep water flowing during storms, according to Rezende, and is coordinating with the San Diego Lifeguard Service’s swiftwater rescue team to clear vegetation, open gates and remove obstructions so rescuers can reach anyone trapped by rising water.

San Diego County is taking similar precautions, tracking weather forecasts and sending crews to clear drains and inlets, trim trees and sweep streets in unincorporated areas, county spokesperson Donna Durckel said.

Further north, Rep. Mike Levin recently secured a $26 million federal grant to repair the levee system protecting the San Luis Rey River near Oceanside and to clear sediment buildup from the channel — repairs residents had been promised since 1970 but never received.

Pollution remains a persistent headache as well. Communities in south San Diego and neighboring Imperial Beach regularly deal with sewage and industrial contamination flowing from the Tijuana River. Heavy rain can overwhelm treatment plant capacity, sending more untreated waste downstream and fouling coastal waters.

Aging dams add to the risk

San Diego’s flood-control challenges are compounded by dams that average 100 years old, among the oldest in the country. Four are flagged for safety concerns requiring repair, including the dam at Lake Hodges, which state regulators rate “unsatisfactory” with “extremely high downstream hazard potential,” according to the California Division of Safety of Dams.

That dam needs to be rebuilt entirely, but a plan to complete the project by 2029 collapsed after cost estimates jumped from $275 million to as much as $697 million. The San Diego County Water Authority, which had agreed to split the cost, pulled out once the price more than doubled.

The city is now moving forward on its own. In 2024, the City Council approved a 10-year, $100 million contract to manage its Dam Safety Program, expanding the team responsible for inspections and maintenance and drawing up 36 near-term repair projects, according to city spokesperson Jennifer McBride. Full upgrades across the system are expected to cost $3 billion over the coming decades.

In the meantime, the state has directed the city to keep Lake Hodges below 280 feet to reduce the chance of dam failure during a major storm. Some residents argue the lower water level is hurting wildlife habitat and could leave the area more vulnerable during wildfire season — a real concern given that El Niño years can just as easily bring drought as deluge.

Waves to watch

Beyond flooding, forecasters are also eyeing dramatic surf conditions this winter — a mixed blessing for surfers and coastal managers alike.

Rising sea levels driven by warmer water expansion, shifting atmospheric pressure systems and altered ocean currents can combine with unusually high “king tides” to produce punishing swells.

Such waves have caused serious damage before. During the 1982-83 El Niño, massive surf destroyed the historic Scripps Pier beyond repair and flooded the landmark Marine Room restaurant. “There was a lot of coastal damage because the big waves coincided with astronomically high tides,” Gershunov said. “The risk of coastal damage and erosion is higher again this winter.”

Still, he noted a silver lining: “I think the surfers who love big waves should be satisfied this winter.”

Original source: CalMatters