LOS ANGELES (AP) — Scientists dub it California’s “other Big One,” a series of storms capable of costing three times as much as a severe Southern California earthquake.
The storms have happened before, lasting 45 days in the winter of 1861-62. They left nearly a third of taxable land under water and caused the state to go bankrupt.
If a similar scenario played out today, flooding in the Central Valley could stretch 300 miles long and more than 20 miles wide, a report released Thursday by the U.S. Geological Survey found. The storms also could cause hundreds of landslides and serious damage in the state’s major population centers.
“Storm are less sudden, less dramatic, and thus loom smaller than earthquakes do in the imagination of risk,” the report said. “But the evidence shows these storms do pose a real risk for California, in some ways far greater than that of earthquakes.”
A team of 117 scientists, engineers and public policy and insurance experts worked for two years to create the hypothetical scenario. They met in Sacramento on Thursday to discuss the report and were not available to comment.
The report raises questions about authorities’ ability to handle such a disaster and aims to be used for preparedness.
Researchers named the weather event “ARkStorm,” after the atmospheric rivers that draw warm, moist air from the Pacific Ocean and turn that moisture into rain and snow when it reaches the West Coast.
Scientists believe a series of atmospheric rivers were behind the storms of 1861-62, the largest and longest storms in California’s recorded history. Geologic evidence of past floods indicate even bigger storms struck the state long before European settlers arrived.
But with infrastructure development and a population that has grown to 37 million, many of whom live on floodplains and hillsides, a big storm could cause massive destruction to the state.
“There’s just more of us living in more precarious locations, and the risk is just higher,” said Bill Patzert, an oceanographer at NASA’s Jet Propulsion Laboratory who was not involved in the USGS project.
He noted that population and infrastructure density as well as “riskier land use” exacerbated the deadly flooding and mudslides happening in Australia and Brazil.
According to the scenario, heavy rain could cause flooding in the Sacramento-San Joaquin Delta, and 50 levees could be breached. Some 1.5 million residents in inland and delta regions would be forced to evacuate.
The report details the extent of potential devastation to crops and livestock in the state’s farmlands and estimates the cost to replace them. It also considers high surf damage and erosion to the sensitive coastline, as well as the perils of debris flow and flooding to California’s roads, bridges, dams and wastewater treatment facilities.
In all, researchers estimated the losses and damages by a catastrophic storm could cost on the order of $725 billion, nearly three times the cost of a 7.8-magnitude earthquake hitting Southern California.
In May 2008, the USGS released a report playing out such a temblor. It became the basis for an earthquake drill billed as the largest in U.S. history, aimed at testing the preparedness of governments, emergency responders and residents.
Patzert said the report highlights the importance of being prepared.
He pointed out that an unusually wet December dumped 10 inches of rain in Los Angeles — the same amount that flooded the city in 1938 and led to the paving of the Los Angeles River. He said putting in flood control helped the city to withstand the recent storm.
“You learn lessons and you prepare for the next one,” Patzert said. “What could have been the great flood of 2010 turned out to be nothing more than a great photo opp.”