What Else Except An Earthquake Could Cause The “Big One”

At this time of year, drought and wildfires are the primary causes of death and destruction reported in the media. There is, however, another type of disaster that might strike the state of California and cause far greater economic harm than a major San Andreas Fault earthquake.

Scientists have concluded that as the planet warms due to human activity, a month-long superstorm that would dump unprecedented amounts of precipitation on Northern and Southern California is becoming increasingly likely. The study indicates that the annual likelihood of one happening is already close to one in fifty. The more greenhouse gases we release into the air, the greater the risk becomes.

Atmospheric rivers, the storms that move in from the Pacific and are frequently referred to as “Pineapple Express” events, can bring greater payloads of precipitation because warmer air contains more moisture.

Huge storms powered by atmospheric rivers have before hitting California. It was so bad in Sacramento that Governor Leland Stanford had to use a rowboat to his inauguration ceremonies in January 1862, as documented by the Sacramento History Museum, and the Central Valley was turned into an inland sea. San Francisco is also the temporary home of the State Legislature.

After devastating floods in the past, the state began damming rivers and constructing bypasses to divert water away from populated areas. All of this infrastructure makes it less probable that the 19th-century storm would wreak widespread harm if it struck today. Although the state is more developed than the rest of the country, with larger cities, more valuable farms and companies, and more people, the potential repercussions remain high.

The bright side is that many legislators and planners are already aware of the dangers. The state’s Department of Water Resources aims to use the new scientific results to revise the state’s flood plans, as I reported for The New York Times on Friday. They will use supercomputers to meticulously plan out the path that all of the rainwater will take as it trickles down rivers and spreads across the landscape.

Levees in urban regions of California’s Sacramento and San Joaquin Valleys are being fortified to withstand the kind of catastrophic flooding that occurs once every 200 years or has a 0.5 percent probability of happening in any given year.

However, as I discovered when researching this interactive article, there is a flip side to all of these preparations: they have made flood risk something that many Californians no longer think about.

That’s encouraging on one level, as most of us have more pressing concerns each day than fretting over Mother Nature’s wrath. However, denial of your location’s potential dangers comes with its own set of risks. A person could disobey evacuation orders, put little stock in weather predictions, and choose not to get flood insurance.

During a recent tour of Sacramento’s flood-management works, I spoke with Ricardo Pineda, a retired state engineer. He said that when the government is involved with these levees, most homeowners trust that we are doing the right thing and that it is safe for them to put their life savings in a home.

“They adore walking their dogs on the levee,” Pineda remarked. But “do they have a plan to deal with the economic fallout of floods on the scale seen in New Orleans?”

The River Islands master-planned neighborhood in Lathrop, California, is located on the San Joaquin River in an area that was severely flooded during a storm in 1997. Without using public funds, the developer constructed extra-wide levees to safeguard the picturesque neighborhoods and well-kept roadways.

River Islands Development president Susan Dell’Osso told me that many of her buyers were from the Bay Area and asked pointed questions about the quality of life and education in the Central Valley.

The people “never ask questions about flooding,” Dell’Osso remarked. She claims that she attempts to teach them more about the subject. “I don’t think they realize there’s a risk,” you say.

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