Fatal flash floods along the Guadalupe River in Texas show catastrophic tolls that could potentially be taken away by such a disaster, and California could face similar dangers when extreme weather hits.
As shown in past flooding in some states, such as the Los Angeles area, Central Valley and the Central Coast, the arrival of downpours and rapids can create danger to lowland areas along rivers and streams.
Around 20 people died statewide when a series of extreme winter storms struck California in 2023. This includes those who were washed away by floods or killed by rock slides, falling trees or car crashes.
“These risks lie here,” said UC Irvine Professor Brett Sanders. “We have a lot of flash flood possibilities. There are hilly areas. There are streams that spread out and you can catch surprises with the water.”
California history is dotted with examples of dangerous flooding storms, such as the fatal Los Angeles flooding in 1934, and the 1861-62 flooding that saw catastrophic debris flow after the heavy rain that hit the Santa Barbara County town of Montecito in 2018.
Floods in Southern California have killed dozens of people. The bus was stuck at 43rd west near Raymart Boulevard. This photo was published in the Los Angeles Times on March 3, 1938.
(Los Angeles Times)
Flash floods in Texas were among children and counselors who were in summer camps when more than 100 people died, others went missing and the floods swept the area. Authorities described it as “100-year flow.”
Sanders said he looked up a map of federal hazard zones generated by the Federal Emergency Management Agency when considering factors that contributed to his high death toll. Judging by the map, he said many of the summer camp cabins are located within federally designated “floods” and are at high risk.
“The waterways are areas where you know the water moves very quickly, so we know it’s a really dangerous place,” Sanders said.
“There were people who did harm and didn’t know they were doing harm,” he said. “There was a breakdown somewhere along the way in terms of understanding risk and ability to take action in a timely manner.”
There are many buildings in California’s flood hazard zone, but buildings are rarely permitted on flood roads here.
“It appears that more could have been done, especially during the time when rain was predicted, to raise awareness about the risk of sleeping overnight next to a flood-prone stream,” Sanders said of the Texas flooding.
Daniel Swain, a climate scientist in UC Agriculture and Natural Resources, said the types of storms that tend to unleash floods in California are different from the severe thunderstorms that caused floods in Texas.
“But the level of the flood and the sudden and devastating effects of it can be very well replicated in California,” Swain said at a media briefing. “It’s particularly likely to occur in winter storm sequences, which are intense atmospheric rivers.”
He said such storms caught up in the Pacific Ocean carrying large amounts of water vapor would usually be massive.
“So it will not only affect one section of a particularly vulnerable basin, but it will probably affect many basin simultaneously. “But that’s probably a little more predictable.”
Swain said in some cases, thunderstorms have been embedded in major winter storms. For example, the extreme storm that produced the flow of Montecito debris in 2018 was as intense as the Texas deluge, but not long.
Residents will be watching Studio City’s landslide and flooded street closures in 2023.
(Irfan Khan/Los Angeles Times)
The difference between Montecito, he noted, is that the rain loosened the hillside that had been burned by Thomas Fire.
“Similar idea: Very localized, very extreme convective rains are completely overwhelming and almost unimaginable amounts of water in the cloud explosion,” Swain said.
Scientific predictions show that climate change overlays humans has increased the risk of extreme flooding in California and elsewhere. The warmer air can hold more water vapor, allowing storms to throw away more rain.
Los Angeles County is part of the state facing serious flood risk. L.A. County Public Works spokesman Kerjon Lee said the county has been investing in flood protection and stormwater capture efforts in recent years to increase the region’s resilience to the impacts of climate change.
“We are using climate forecasting to develop a robust flood prevention network to help our communities withstand flooding and other extreme weather events and recover as quickly as possible,” Lee said in an email. “Los Angeles County Public Works is working to educate the public about flood risk, so residents can develop emergency plans through the purchase of flood insurance and reduce financial risk.”
A 2022 study estimated that researchers, including UC Irvine’s Sanders, could be affected by a 100-year flood in the Los Angeles Basin, revealing greater risks than previously estimated by federal emergency management officials.
Researchers found that black and low-income communities are particularly hard hit by such floods because they are disproportionately associated with low-lying areas.
The SUV was one of many stuck vehicles stuck in mud and much of the flood after Tropical Storm Hillary sent flood damage Sunday night in Cathedral City in 2023.
(Gina Ferazzi / Los Angeles Times)
Sanders said the team’s analysis showed the area faced a major flood risk, but California has become stronger in the regional planning process, which limits flood construction.
“There are a lot of the same dangers in California, but I think there are different levels of regulations that have probably affected what these storms could potentially be exposed,” Sanders said. “I think California has a stronger planning and flood management mechanism in place than Texas, which limits that risk.”
But the state has a variety of flood-prone campgrounds along rivers and streams, Sanders said. And there are many homeless people who live along rivers and flood control channels that are at risk in the event of floods.
Some of the victims during the recent floods were drivers who tried to drive fast-moving water, Sanders noted. “All kinds of low intersections that often turn into water rapids, it may look shallow [can] You’ll pass through your car, but in many cases the car wipes out the road, and then people lose their lives. That’s another risk that Californians face. ”
Sanders said the loss of life in the Texas disaster points to “lack of risk communication, lack of risk awareness.” He said the disaster demonstrates the importance of coordination between federal, state and local governments, and coordination between property owners to keep people safe in the event of extreme flooding.
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