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Experts warn that a major, California ‘megaflood,’ is possible if the climate changes as expected

FEMA believes that California has a similar risk of flooding as it does wildfires because the affected areas are connected by water.



Flooding may seem like an unusual cause for concern as California struggles with the spread of wildfires and a severe drought. However, a recent study cautions that the state may see a “megaflood” in the near future, potentially placing millions of people at danger throughout the state.

According to the research, which was released on Friday in the journal Sciences Advances, the likelihood that California would see an event “capable of triggering catastrophic floods” within the next 40 years has already increased by twofold.

The report recognizes that California experienced two historically severe droughts between 2012 and 2021, and that the state is “more acclimated to water shortage than plenty in the modern period.” The state is reportedly also vulnerable to periods of excessive rainfall, according to historical and paleoclimate evidence; climate change may, however, hasten the probability of a significant storm in the future.

The report states that during the 20th century, the state saw excessive precipitation and catastrophic subregional flooding disasters several times, particularly in 1969, 1986, and 1997. Although those occurrences raise the “latent potential” for a large flood in the future, the study found that “none have matched… the benchmark ‘Great Flood of 1861-1862’.”

It was stated that this particular event “was characterized by weekslong sequences of winter storms” that “produced widespread catastrophic flooding across virtually all of California’s lowlands — transforming the interior Sacramento and San Joaquin valleys into a temporary but vast inland sea nearly 300 miles in length.”


According to the study, “ARkStorm,” a 2010 California state-wide catastrophe scenario sponsored by the U.S. Geological Survey, was inspired in part by the effects of the “Great Flood.”

According to further research, such an occurrence “would undoubtedly create widespread, catastrophic flooding,” which may force millions of people to flee their homes, permanently close vital transit routes, and result in “almost $1 trillion in overall economic damages,” the report stated.

According to the study’s authors, the results show that climate change “is robustly increasing both the frequency and magnitude of extremely severe storm sequences capable of causing megaflood events in California,” making such an event more likely. “Our analysis suggests that the present-day (circa 2022) likelihood of historically rare to unprecedented 30-day precipitation accumulations has already increased substantially and that even modest additional insolation could further increase the likelihood of such accumulations,” the researchers wrote.

Despite the bleak picture, the research stated that California may take certain steps to “mitigate harm during a 21st century California megaflood.” Levee setbacks and floodplain restoration are a couple of these strategies that could reduce flood risk in metropolitan areas, the report added. The document also suggested updating emergency evacuation and contingency plans to “accommodate the likelihood of inundation and transportation disruption going much beyond that which has occurred in the past century.”