Study: Risk of ‘ArkStorm’ flooding vastly increased

LOS ANGELES (CNS) — The effects of climate change have doubled the chance of a catastrophic storm and devastating flood like the one that ravaged the state, in 1862, with a similar event likely to displace millions of people and leave areas like Los Angeles under water, according to a UCLA study released, Friday.

“In the future scenario, the storm sequence is bigger in almost every respect,” Daniel Swain, UCLA climate scientist and co-author of the paper published in the journal Science Advances, said in a statement.

Researchers studying a socalled “ArkStorm” scenario — a reference to a flood of “biblical” proportions — found that a modern-day storm mirroring the 30-day deluge of rain that occurred, in 1862, would generate 200% to 400% more runoff in the Sierra Nevada Mountains. The increase is due to more precipitation falling overall, and more of it falling in the form of rain, rather than snow, researchers said.

“On 10,000-foot peaks, which are still somewhat below freezing even with warming, you get 20-foot-plus snow accumulations,” Swain said. “But once you get down to South Lake Tahoe level and lower in elevation, it’s all rain. There would be much more runoff.”

According to researchers, if such a storm event were to occur, the dramatic increase in precipitation and runoff would cause “devastating landslides and debris flows.”

Researchers noted that the Great Flood of 1862, occurring before the development of any flood-control infrastructure, led to flood waters that were 300 miles long and 60 miles wide.

Even with modern flood-control measures, a similar event, today, would leave parts of cities such as Sacramento, Stockton, Fresno and Los Angeles “under water,” causing an estimated $1 trillion in damages.