4 things to know about SoCal’s flood systems in the wake of the Texas tragedy

The flood tragedy in Texas has claimed over 100 lives — including at least 27 girls and staff at a summer camp — with an additional 161 people reported missing as of Tuesday.

It’s one of the nation’s deadliest floods this century and is spotlighting the growing numbers of flood deaths in the U.S., driven by heavier rainfall as the warming atmosphere holds more water.

Southern California has not been immune to serious injuries and deaths from floods.

In the wake of the tragedy in Texas, LAist set out to get answers about our local situation here.

We found that while flood infrastructure has come a long way since historic disasters, a warming climate is contributing to more frequent, powerful storms that heighten the risk of flooding in Southern California. Officials are six years behind schedule to fix one of the riskiest dams in the nation, sitting just above cities right here in Southern California.

But experts say there are steps you can take to protect yourself should disaster strike.

Flood infrastructure has improved a lot — but rainstorms are getting wetter, and local areas still flood

Flooding used to be a regular occurrence in Southern California, both from rains and — in one major case — a manmade disaster.

Nearly a century ago, L.A. County suffered the deadliest dam failure in U.S. history. Design flaws caused the St. Francis Dam to collapse in 1928, killing at least 431 people from a flood that swept from Santa Clarita to Ventura.

The region has upgraded its flood control system since then by building major dams, water-holding basins and channelizing major rivers with concrete.

Some areas of the region do still flood during major storms — including one in 2005 that killed 10 people in a landslide and caused hundreds of millions in damage.

Even the modern infrastructure can still be inundated by a massive rainstorm.

“That system may be overwhelmed by a storm [that’s] the size and scope of what we've seen in Texas and what may be forecast as a hundred-year event,” said Kerjon Lee, a spokesperson for the L.A. County Public Works, which manages flood control systems across the county.

Major rainstorms are getting wetter, increasing flood risk

Storms that used to be expected once every 100 years are getting more frequent, experts say.

Frances Edwards, who oversaw emergency preparedness for the cities of San Jose and Irvine, said that, thanks to climate change, we can expect these 100-year storms — like the recent one in Texas — more frequently and in places we wouldn’t expect to be at risk.

“Just because it didn’t happen before, doesn't mean it can’t happen now,” she added. “The warmer the ocean gets, the warmer the air gets. The warmer the air gets, the more moisture it holds, which means there’s more moisture in the clouds when it rains, [and] as the ocean warms, we are going to see much wetter weather than before.”

The county’s draft hazard mitigation plan for 2025, which was made available for public comment this spring, says major rainstorms are expected to worsen with climate change, with a 95% chance of a flooding event each year in L.A. County. The draft plan is expected to go to the county Board of Supervisors for final approval.

We’re home to one of the nation’s highest-risk dams for major flooding

In 2016, the Whittier Narrows Dam above Pico Rivera was designated in the highest risk category nationally for failure — deemed by an official study to be “unsafe” and “critically near failure.”

Failure of the dam could be catastrophic, according to the county’s previous hazard mitigation plan from 2020.

“An intense storm could prematurely open the dam’s massive spillway and flood the area below from Pico Rivera to Long Beach,” the county plan states.

The U.S. Army Corps of Engineers, which manages the dam, classified it as the “highest dam priority nationally because of the risks ‘due to the combination of loss of life with a very high likelihood of failure” during a rare flood event.

An Army Corps construction project to fix the dam was expected to finish by 2025, the county plan stated.

The work is now six years behind schedule, with an estimated completion in 2031, a spokesperson for the city of Pico Rivera told LAist in an interview.

The Army Corps of Engineers did not have someone available to answer questions on Tuesday, according to a spokesperson.

But Pico Rivera spokesperson Javier Hernandez described to LAist the latest briefing the city got from the Army Corps and its contractor.

Major construction is expected to start late next spring and early summer, and be completed by the end of 2031, Hernandez said. The Army Corps cited the COVID-19 pandemic, economic downturn, supply chain shortages, and increased costs to obtain the large amount of raw materials as the main reasons for the delay, he said.

At the same time, Hernandez said heavier rainfall is “testing the limits of the dam.”

“The big challenge the Army Corps has outlined is, building such a significant project while trying to best plan for weather and weather conditions,” Hernandez said. “Hopefully, we don’t have the 500-year storm between now and completion of this project.”

How to prepare and protect yourself from flooding

Edwards, the former emergency planning director, said it’s important to pay close attention to weather forecasts and news reports before and during major storms — and to evaluate the area around your home for flood risks.

“Look at your environment, and ask yourself, if there’s a whole lot of rain that’s going to come in a hurry, is it going to come racing down the side of that mountain…or is it going to clog up storm drains in my area? What’s my risk in my location?” she said.

L.A. County emergency officials set up ready.lacounty.gov to help prepare for all kinds of disasters, including floods, said Lee of the public works department.

The flood preparation page includes links to maps of flood risks in the region.

“Severe flooding could happen almost anywhere in L.A. County. Just because you live adjacent to the L.A. River doesn't mean that there's not risk there,” Lee said.

People should try to keep three to four days of food and supplies at home in case they get stranded and are awaiting help, Edwards said. It’s also good to arrange in advance to have multiple people check in to make sure you’re OK, she said.

If someone doesn’t communicate back, that’s a trigger they may be stranded and to contact authorities, she said.

“You should still have a buddy system, so somebody knows that they haven’t heard from you,” Edwards said. “Asking for help is extremely important for everybody. I don't care how young and able-bodied you are.”