Megastorms Could Flood Massive Portions of California

Posted on Thursday, January 3rd, 2013 by Hui Qian


Scientific American recently published an article on “megafloods”, warning that massive floods caused by atmospheric rivers will likely impact California if climate change continues unabated.

According to Michael D. Dettinger (researcher at U.S. Geological Survey) and B.Lynn Ingram (Earth and planetary science professor at Berkeley), atmospheric rivers—narrow bands of water vapor running a mile above the ocean and extending for thousands of kilometers—are responsible for most catastrophic floods that occur in California every 200 years or so. In 1861, a megastorm hit California after two decades of severe droughts and created a huge inland sea in Central Valley, leaving thousands of human lives and one quarter of the state’s economy destroyed.

The regions that are home to most people in California today were put underwater for several months, and boats became the only means of transportation (see photo).

William Brewer, the author of the book Up and Down California in 1860-1864 wrote, “The entire valley was a lake…. Nearly every house and farm over this immense region is gone.” Three months after the initial flooding, he visited Sacramento and described, “Most of the city is still under water, and has been there for three months…I don’t think the city will ever rise from the shock, I don’t see how it can.”

It is estimated that a comparable event in today’s California would force more than a million people to evacuate and cause $400 billion in lost property and agriculture. Los Angeles County, Orange County, San Diego and the San Francisco Bay Area would be especially susceptible to the negative impacts.

The stakes are high, and though action to reduce greenhouse gas emissions is needed on a global scale, California is doing its part to avert these kinds of crises. The state’s cap-and-trade program will be fully implemented in 2013 and is responsible for meeting almost 20 percent of the GHG reduction target the state has set: returning to 1990 levels by the year 2020. At CalCAN, we will continue our efforts to assure that sustainable agriculture is part of the solution, advocating for resources for sustainable farming practices that help lower agriculture’s GHG emissions, help growers adapt to the coming changes, and protect farmland that can help buffer against flood risk.

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