SUN VALLEY, CA – FEBRUARY 17: A man boards a bus on a flooded road as a powerful storm moves through Southern California on February 17, 2017 near Sun Valley, California. After years of severe drought, heavy winter rains came to the state and
LOS ANGELES – Climate change has doubled the potential for a “catastrophic” flood in California, and further warming could increase that chance even more, according to a new study by researchers at the University of California, Los Angeles. Such a “megaflood” could “result in the displacement of millions of people, the long-term closure of critical transportation corridors and ultimately nearly $1 trillion in total economic losses.”
California has been synonymous with drought in recent decades. According to the state, the majority of California is currently experiencing between “moderate” and “extreme” drought conditions. However, the study published Friday in the journal Science Advances says the state also has a “generally underestimated risk of severe flooding.”
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The researchers used a weather model to simulate what they called a “megastorm event,” a worst-case scenario in a 30-day rainfall period. Climate change has already increased rainfall intensity along North America’s Pacific coast, the study says. The increased temperatures also cause snow accumulation on mountains at higher elevations on average and increase the chance of rain as opposed to snow. The combination of all these factors, researchers say, increases runoff rates that can lead to flash floods.
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“This is particularly true in the region around large or high-intensity wildfire burning areas, which are themselves increasing due to climate change,” the authors write.
The authors emphasize that a “megaflood” like this is the worst-case scenario and that measures are already available to mitigate the risks of such a flood, including floodplain restoration, levee retreat, increased forecasting for reservoir operators, and evacuation plans that take into account the possibility of continuous transport disruptions. The study concludes by saying that “recognizing and mitigating the societal risks associated with this subtly but substantially escalating natural hazard is an extremely important consideration from a climate adaptation perspective.”
