Â鶹ӰÊÓ

Skip to main content

Warming climate could see a future California flood become the world's costliest disaster, study suggests

Share

A new study is offering a dire prediction for the U.S. state of California, where scientists say catastrophic flooding could become twice as likely in the future due to the effects of climate change.

Researchers from UCLA and the National Center for Atmospheric Research completed and published the results of the first part of their "ArkStorm" 2.0 study, looking into possible climate-induced flooding of a "biblical" proportion, also known as "the Other Big One" in reference to an expected major earthquake on the San Andreas Fault.

The study, published on Aug. 12 in the peer-reviewed journal , found that historical climate change has already doubled the likelihood of an extreme storm scenario, with the chance of a "megastorm" expected to increase with each additional degree of global warming this century.

The study projects that end-of-the-century storms will create between 200 and 400 per cent more runoff in the Sierra Nevada Mountains due to increased precipitation, more of which will fall as rain instead of snow.

"In the future scenario, the storm sequence is bigger in almost every respect," Daniel Swain, UCLA climate scientist and co-author of the paper, .

"There's more rain overall, more intense rainfall on an hourly basis and stronger wind."

While droughts and wildfires tend to get a great deal of attention, Swain said Californians might be losing sight of extreme flooding

"There is potential for bad wildfires every year in California, but a lot of years go by when there's no major flood news," he said. "People forget about it."

The state has experienced major flooding in the past, but the researchers say nothing has reached the scale of the Great Flood of 1862, when floodwaters stretched up to 300 miles long and 60 miles wide across California's Central Valley, at a time when no flood management infrastructure existed.

The population of California has increased significantly since then from about 500,000 to , the researchers say.

Were a similar Great Flood to occur now, the scientists say parts of Sacramento, Stockton, Fresno and Los Angeles would be underwater – a disaster to the tune of US$1 trillion in economic losses and larger than any in world history.

Flooding is already taking a toll on west coast economies, with major flooding in British Columbia causing in insured damage, according to the Insurance Bureau of Canada.

The study comes nearly a year after record flooding in November 2021 displaced at least 15,000 people in British Columbia.

Prior to that, the province experienced a record-breaking heat wave over the summer.

Using new high-resolution weather modelling and existing climate models, the study's researchers compared two extreme scenarios: one occurring about once a century under recent historical climates and the other under a projected climate between the years 2081 and 2100.

The scientists say both scenarios would see a long series of storms fuelled by – long narrow regions in the atmosphere that carry water vapour – over the course of a month. The B.C. flooding last November has been tied to the presence of atmospheric rivers.

Climate change increases the amount of rain the atmosphere can hold, on the study says, leading to more water falling as rain, which can lead to immediate flooding.

Referring to the future scenario, Swain said there are localized spots that could get the equivalent of more than 100 inches of water in a month.

Increased runoff could lead to devastating landslides and debris, especially in hilly areas burned by wildfires, the researchers say.

Major interstate freeways such as the I-5 and I-80 would likely shut down for weeks or months, affecting the economy and supply chains globally, the researchers add.

But even if meteorologists and climatologists gave weeks of notice about the flooding, the scientists say it would still not be possible for the five to 10 million people displaced by floodwaters to evacuate their homes.

The researchers highlight that the study was limited due to a lack of organized resources and funding.

Advanced flood simulations done with the support of federal and state agencies are in the works, the scientists say, adding they hope to map where flooding could be worst.

With files from Â鶹ӰÊÓ, The Canadian Press and CNN

CTVNews.ca Top Stories

The British Columbia election campaign is set to officially start today, with Lt.-Gov. Janet Austin issuing the writ for the Oct. 19 vote.

A northern Ontario man is facing a $12,000 fine after illegally shooting a moose near the Batchawan River.

Unusual flippered feet are making their way into the Saint Lawrence River this weekend. Led by underwater explorer and filmmaker Nathalie Lasselin, volunteer divers are combing the riverbed near Beauharnois in Montérégie to remove hundreds of tires that have been polluting the aquatic environment for decades.

A sea lion swam free after a rescue team disentangled it near Vancouver Island earlier this week.

Local Spotlight

Cole Haas is more than just an avid fan of the F.W. Johnson Wildcats football team. He's a fixture on the sidelines, a source of encouragement, and a beloved member of the team.

Getting a photograph of a rainbow? Common. Getting a photo of a lightning strike? Rare. Getting a photo of both at the same time? Extremely rare, but it happened to a Manitoba photographer this week.

An anonymous business owner paid off the mortgage for a New Brunswick not-for-profit.

They say a dog is a man’s best friend. In the case of Darren Cropper, from Bonfield, Ont., his three-year-old Siberian husky and golden retriever mix named Bear literally saved his life.

A growing group of brides and wedding photographers from across the province say they have been taken for tens of thousands of dollars by a Barrie, Ont. wedding photographer.

Paleontologists from the Royal B.C. Museum have uncovered "a trove of extraordinary fossils" high in the mountains of northern B.C., the museum announced Thursday.

The search for a missing ancient 28-year-old chocolate donkey ended with a tragic discovery Wednesday.

The Royal Canadian Mounted Police is celebrating an important milestone in the organization's history: 50 years since the first women joined the force.

It's been a whirlwind of joyful events for a northern Ontario couple who just welcomed a baby into their family and won the $70 million Lotto Max jackpot last month.