Why California's floods may be 'only a taste' of what's to come in a warmer world

The street in front of Antonio Hueso's two-story, yellow-daisy-colored home in Pajaro, about an hour south of San Francisco, turned into a deep muddy river in the early morning hours of March 12. The waters submerged his Ford F-150 truck and his first floor flooded.

"In Pajaro, nothing is going to change because poor people live here," said Hueso, 72, a retired farmworker. He recounts more than three decades of requests from the community for local, state and federal officials to fix the aging levee on the Pajaro River, four miles upstream from his town.

The levee failure forced more than 3,000 Pajaro residents to flee in the predawn darkness. Now, Hueso is beginning the arduous task of renovating his flood-damaged home.

Hueso is just one of the thousands of people across the state reeling from this winter's string of storms that engorged rivers, breached levees and even restored a dried-up inland lake in California's Central Valley.

Climate scientists say heavy rain and snow storms brought on by atmospheric rivers that park over the state are nothing compared to what's predicted in a warmer world. With aging levees and a wetter future ahead, some Pajaro residents question whether this part of California is a viable place to call home.

Over the nearly five decades Hueso's lived in Pajaro, this is the second time he has had to renovate his home. He lived through an equally devastating flood in 1995. Officials say a significant levee update could begin as soon as late 2024. Hueso questions, though, whether such plans will account for human-caused climate change and the increased frequency and ferocity of the storms expected.

Heuso is now considering leaving. "I'm going to fix my house, and when people forget about the flooding, I will sell my house and move to Madera or Fresno," he said.

'Nowhere near' a worst-case scenario

Climate scientists warn that what Californians have lived through in recent months — atmospheric river after atmospheric river, catastrophic flooding, and one of the largest winter snowpack in years — is just a preview of what's to come, with exponentially worse flooding predicted in future years. When atmospheric rivers reach land, they act like a hose dumping heavy moisture on the land, which can cause issues like flooding, landslides and power outages.

"As disruptive as this year's events have been, we're nowhere near to a plausible worst-case storm and flood scenario for California," said UCLA climate scientist Daniel Swain.

Before cities and farmland dominated valleys and flatlands across the state, much of California was perpetually wet, with a vast system of rivers and waterways running through its core. Catastrophic floods reshaped the landscape every few centuries.

Swain is unequivocal about the links between a warming climate due to the burning of fossil fuels and the significant increase in extreme flooding. A 2022 study Swain co-authored found that the warming climate has already doubled the probability of a megaflood caused by a string of extreme atmospheric rivers.

Every degree of new warming increases that likelihood even more, he said.

In other words, what was once considered unlikely to happen in our lifetimes "has become quite likely," Swain said. He wouldn't be surprised, he said, if as many as four megafloods happened in this century.

"We're not necessarily talking about 100 years from now. We're talking about the next 20 or 30 years," Swain said. "We've gotten a taste of widespread flooding, but I do think it's only a taste."

The West Coast has already been hit by more than 30 atmospheric rivers since October, according to the Scripps Institution of Oceanography. But to be categorized as part of Swain's extreme scenario, those storms would have had to take place in rapid succession, with little or no time in between.

This year, by contrast, there were breaks of up to a month between each storm. Despite the storms' havoc, none that hit California were technically considered "extreme," Swain said.

"This winter, we've gotten lucky, believe it or not, because things could have been significantly worse than they were," he said. "It is possible to have years where there are multiple atmospheric rivers in a row that are much stronger than what we saw at any point this year."

Swain said the recent storms dropped only about half the precipitation and less than a quarter of the runoff than in the "plausible worst-case scenario" he describes in his study. The resulting "megaflood" conditions, he said, would cause widespread levee failures that would impact not just agricultural land but urban areas, too.

A KQED analysis of the National Levee Database found that only 10% of the nearly 600 levees in the greater Bay Area have a flood-risk rating. The small percentage that do have a rating includes the breached levee on the Pajaro River, which is rated "moderate." Another levee on the Salinas River failed in January also had a "moderate" rating. Other levees rated "moderate" in more urban areas like San José are also at risk of significant flooding.

"We've definitely gotten a taste in some areas of what a much lesser version of this would look like," Swain said. "But we need to be preparing for and stress-testing our infrastructure for much greater events than the ones you've seen this year."

Flood modeling

California is taking Swain's predictions seriously. Michael Anderson, the state's climatologist, is trying to convince the California Department of Water Resources to fund a flood-modeling project in partnership with Swain and the Oak Ridge National Laboratory. The goal would be to understand the impact an extended series of extreme storms would have on existing infrastructure, like levees.

"This is a flood model that would resolve the flood risk at one corner of someone's house versus another corner, for example," Swain said. "That's how detailed it would be for the whole state."

The project involves recording several factors, including soil conditions, river flows, forecasted precipitation, real-time snowmelt and runoff, in an effort to calculate the extent of flooding that could result from storms.

Such predictions could help the state understand what areas are at the greatest risk of flooding and who should evacuate, Anderson said.

"The other thing we can do is start saying, 'Wow, if that happened, how do we recover?"' Anderson said. "How do we take that really horrible situation and try and turn it into a chance to maybe rethink how we do some things?"

Once approved, the project could take up to a year to complete and cost about half a million dollars. Anderson acknowledges such modeling is coming too late for the many thousands of people already displaced by this winter's floods.

"Unfortunately, Mother Nature kind of beat us to the punch here," he said. Anderson believes such modeling, though, could help the state scale the "right level of response" for future floods.

Living in the shadow of an aging levee

The climate crisis is all too real for Armando Alvarado, who now lives in the shadow of a broken levee. A week after flood waters covered Pajaro, the 22-year-old returned home to find his garage coated with a thick layer of sticky, putrid mud. The rest of the elevated home his family rent was unscathed.

The wet mud in the garage ruined a number of family heirlooms, including his collection of red, white and black ostrich-leather ranchero boots.

"They were emotional gifts from my family in Mexico, like uncles that passed away," he said.

Alvarado said he's worried about how costs to repair the damage will affect his family's rent in an area of California where a one-bedroom apartment can cost as much as $2,800.

Denia Escutia, a high school senior who lives a few blocks away from Alvarado, woke up early in the morning on March 12 to the sound of water pouring into Escutia's purple bedroom adorned with K-pop posters.

"I touched my feet to the rug, and the rug was wet," said Escutia, who prefers not to use pronouns. Escutia's entire house was filled with a thin layer of smelly, muddy water.

"I woke up my dad, and we started unplugging a bunch of stuff," Escutia said.

Now, weeks later, the climate activist is questioning whether there's a future in Pajaro because of the familiar risks — including droughts, heat waves and flooding — that will likely only worsen with a warming climate.

Escutia, whose hometown is Pajaro, dreams of living safely on a nearby hill, surrounded by family. But Escutia fears Pajaro has no future because of climate change and the decisions made by those in power that devalue the people who live in the community.

"I think Pajaro deserves climate justice," said Escutia. "I call this my home, but is it really my home if they don't want to help us?"

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