They usually bring beneficial rainfall to drought-prone regions like California but could quickly become hazardous with a warming climate. An atmospheric river is a long, narrow region of heavy moisture in the atmosphere that can transport moisture thousands of miles, like a fire hose in the sky. The new study shows a rapid increase in the likelihood of week-long, recurring strong-to-extreme atmospheric rivers during the cool season.
Both are and will continue to occur in California. "When this (flood) occurs again, the consequences would be wildly different than they were back in the 1860s," Swain said.Ĭlimate change increases the amount of rain the atmosphere can hold and causes more water in the air to fall as rain, which can lead to immediate flooding.
Now, the state's population is over 39 million. Many of today's major cities with millions of residents are built directly on top of the ancient flood deposits, Swain added, putting far more people in harm's way.Ībout 500,000 people lived in California in 1862. "We find that climate change has already increased the risk of a (1862) megaflood scenario in California, but that future climate warming will likely bring about even sharper risk increases," the study warns. Swain warns a megaflood like this will happen again, but worse and more frequent. In addition, one-fourth of California's economy was obliterated, resulting in a state-wide bankruptcy. Repetitive atmospheric rivers dropped warm rain for 43 days thereafter, dumping water down the mountainous slopes and into the valleys.įour thousand people lost their lives, one-third of the state's property was destroyed, a quarter of California's cattle population drowned or starved, and one in eight homes were a complete loss by floodwaters. The catastrophe began in December 1861, when nearly 15 feet of snow fell in the Sierra Nevada. The Central Valley, roughly the size of Vermont and Massachusetts combined, produces a quarter of the nation's food supply, according to the US Geological Survey. The area with the most destruction would be the Central Valley of California, including Sacramento, Fresno and Bakersfield, the study's authors project. Xingying Huang, one of the authors of the study, made this loop, which illustrates the water vapor transportation and potential precipitation accumulation at selected time slices during the 30-day scenario. The study said atmospheric rivers could become consecutive for weeks on end, like seen in this animation. Louis, and even in California's Death Valley National Park.Ĭalifornia is prone to these floods from atmospheric rivers naturally, and major floods from them have happened before - but climate change is upping the ante, and millions of people could be impacted. But experts say climate change is increasing the likelihood of these catastrophic disasters, causing them to occur more like every 25 to 50 years.Ĭlimate change supercharges heavy rain events, making flash floods occur more regularly, as has been noted several times this summer in Eastern Kentucky, St. These massive floods, which experts say would turn California's lowlands into a "vast inland sea," might have previously happened once in a lifetime in the state. Louis area and Kentucky, but across a much wider area, such as the entire state of California. And experts say it would be unlike anything anyone alive today has ever experienced.ĭaniel Swain, a climate scientist with UCLA and a researcher involved in the study, describes a megaflood as, "a very severe flood event across a broad region that has the potential to bring catastrophic impacts to society in the areas affected." He said a megaflood is similar to the 1,000-year flash flood events seen this summer in the St. It's actually the exact opposite.Ī new study by Science Advances shows climate change has already doubled the chances of a disastrous flood happening in California in the next four decades. Many Californians fear the "Big One," but it might not be what you think. It could be the most expensive natural disaster ever. A new study warns that a disastrous megaflood may be coming to California in the next 40 years.
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