This is a re-post from Yale Climate Connections by Jeff Masters
A sequence of nine atmospheric rivers hammered California during a three-week period in January 2023, bringing over 700 landslides, power outages affecting more than 500,000 people, and heavy rains that triggered flooding and levee breaches. On a statewide basis, about 11 inches of rain fell; 20 deaths were blamed on the weather, with damages estimated at over $1 billion.
But the storm damages were a pale shadow of the havoc a true California megaflood would wreak.
The Golden State has a long history of cataclysmic floods, which have occurred about every 200 to 400 years — most recently in the Great Flood of 1861-62. And a future warmer climate will likely significantly increase the risk of even more extreme floods. In particular, a 2022 study found that, relative to a century ago, climate change has already doubled the risk of a present-day megastorm, and more than tripled the risk of a trillion-dollar megaflood of the type that could swamp the Central Valley.
Given the increased risk, it is more likely than not that many of you reading this will see a California megaflood costing tens of billions in your lifetime.
This is the third part of a three-part series on California’s vulnerability to a megaflood. Part One examined the results of a 2011 study introducing the potential impacts of a scenario, known as “ARkStorm,” which would be a repeat of California’s Great Flood of 1861-62 — though the study did not take climate change into account. Part Two looked at how California is preparing its dams for future great floods. Here, in Part Three, we’ll look at the increasing future threat of a California megaflood in a warming climate.
