$1.2 Trillion National Flood Insurance Program: The 100-Year Flood
The 100-year flood is projected to occur, on average, once a century, a once-in-a-lifetime event.
According to Slate, these probabilities are also used in modeling the absolute worst cases, such as California’s ARkStorm scenario—a 2010 U.S. Geological Survey project that imagined how a month of constant rain might turn the Central Valley into a giant lake, flooding 1 in 4 of the state’s buildings, forcing the evacuation of 1.5 million people, and causing more than three times as much damage as the better-known nightmare earthquake popularly known as “The Big One.” In addition to offering a potent biblical allusion, ARk stands for “atmospheric river 1,000,” because scientists originally thought those levels of precipitation would occur once every 500 to 1,000 years.
