“Megadrought” is arguably the biggest weather concern in the West right now, amid the constant threat of wildfires and earthquakes. But a new study warns that a new crisis is looming in California: “Megafloods”.
Climate change increases the risk of future flooding that could submerge multiple cities and displace millions of people across California, according to a new study released Friday.
It says a month-long extreme storm can bring yards of rain — over 100 inches in places — up to hundreds of miles from California. Likewise, there have been unrelenting storms in the past, before the region became home to tens of millions of people.
Now, every degree of global warming dramatically increases the likelihood and magnitude of the next megaflood, the study said.
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In a future scenario, where the flood hits a hotter Earth, “the storm surge is greater in almost every way,” Daniel Swain, UCLA climate scientist and co-author of the study, said in a press release. “There’s more rain overall, more intense hourly rainfall and stronger winds.”
Climate change a factor in megafloods
In fact, the study found that climate change is making such catastrophic floods twice as common.
Swain said such massive floods have occurred in California every century or two for the past millennia, and that the current risk of such events has been significantly underestimated.
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Long before climate change, the Great Flood of 1862 in California stretched 300 miles long and 60 miles wide. According to the study, a similar flood would now displace 5-10 million people, shut down the state’s major highways for weeks or months with huge economic consequences, and flood major cities in the Central Valley and parts of Los Angeles.
The study builds on the 2010 “ArkStorm Scenario,” which is named after the atmospheric rivers that would feed the flood — one of biblical proportions. This is the first part of a plan to return to that scenario, known as ArkStorm 2.0.
Massive California Flood Would Be a $1 Trillion Disaster
According to UCLA, a flood like that of 1862 would be an estimated $1 trillion disaster.
“Parts of cities such as Sacramento, Stockton, Fresno and Los Angeles would be under water even with today’s extensive collection of reservoirs, levees and bypasses. It is estimated that it would be a $1 trillion disaster, greater than at any time in world history, ” according to the statement.
With droughts and wildfires getting so much attention, Californians may have lost track of the extreme flooding, Swain said in the release. “There is the potential for serious wildfires in California every year, but many years go by without major flood news. People forget about it,” he says.
The researchers used new high-resolution weather models and existing climate models to compare two extreme scenarios, according to UCLA: one that would occur about once a century in the recent historical climate and another in the projected climate of 2081-2100.
Both would involve a long series of storms fueled by atmospheric rivers over the course of a month.
What are Atmospheric Rivers?
Atmospheric rivers are ribbons of water vapor that stretch thousands of miles from the tropics to the western US. Spanning 250 to 375 miles in width, they provide the fuel for the massive rain and snow storms that can cause flooding along the west coast.
While beneficial to the water supply, such events can wreak havoc on travel, cause deadly mudslides and cause catastrophic damage to life and property, according to the National Oceanic and Atmospheric Administration.
Studies show that climate change will make atmospheric rivers warmer, more intense and more frequent.
Friday’s study was published in the peer-reviewed journal Science Advances, a publication of the American Association for the Advancement of Science.
This Article Originally Appeared on USA TODAY: ‘Megafloods’ Could Devastate California, New Study Says
