'Megastorm' could hit area as hard as a 'quake

USGS 'multi-hazards' expert warns of probable repeat of huge storms of history, only perhaps more frequent

An unimaginably big "megastorm" could hit the Bay Area and California as hard or harder than an earthquake, a researcher with the United States Geological Survey (USGS) warned Thursday in Menlo Park.

Dale A. Cox heads an interdisciplinary scientific team investigating anything on Earth that can go wrong -- sometimes very wrong.

Speaking at noon to USGS colleagues and staff and to the public Thursday evening, Cox outlined the possibilities and impacts of what he calls an ARkStorm. The term is a play on "Noah's Ark" based on the initials AR. Those stand for a relatively new meteorological term: an "atmospheric river," meaning dense moisture-laden storms.

He said such megastorms seem to occur every 200 years or so and involve literally weeks of torrential rains often accompanied by hurricane-force winds of up to 125 miles per hour.

But with global warming their frequency could increase, he said.

The combined impact on both lowlands and forested hills, and on highways, homes and commercial buildings, would be devastating, Cox said in an interview with the Weekly preceding his talks at the USGS Menlo Park facility on Middlefield Road.

Some ARs are modest, more like atmospheric streams, such as one last September that took out his favorite Chinese pistachio tree in his Sacramento back yard, he said.

Cox is project manager for a USGS-sponsored "Multi-Hazards Demonstration Project" that involves other agencies involved in the functioning of all aspects of the planet.

In addition to its weather studies, the group hosted "The Great Southern California Shakeout" in 2008 that explored effects of a major earthquake -- becoming the largest emergency-response exercise in U.S. history.

He earlier teamed with Lucy Jones and Mike Shulters of USGS to create "Urban Earth," an effort to combine knowledge from geology, hydrology, geography and biology in order to assess "the effect of the city on the Earth and the Earth on the city." That project led to the Multi-Hazards Demonstration Project.

Cox and Jones coordinated more than 300 scientists and experts in a major earthquake scenario and drill in Southern California in 2008; a "Firestorm Analysis" project that assessed the impact of ash chemistry and endangered species recovery; and a real-time "debris flow warning system" in time for the first rains.

His group presently is "trying to recreate the storm of 1861" that walloped both Northern and Southern California, using both "paleoflood" evidence on the ground and sources such as ship's logs and diaries that described the storm. At the time there were only four known rain gauges in California, he said.

Such storms can produce a downpour 300 to 400 percent of normal.

"It rained for weeks," Cox said of the 1861 deluge.

The storm's impacts were also immense, even with the small population.

The city of Aguamansa, ironically "calm waters," on the Santa Ana River in Southern California was one of the largest cities in the state at the time.

"It was obliterated," he said.

There is evidence of earlier storms in 1418 and 1605, "no longer in the living memory of the public." Smaller, more recent AR storms occurred in 1969 and 1986, he said.

The "Pineapple Express" is a term applied to such storms moving in from the direction of Hawaii, but it is more frequent to have them come in from the south, Cox said.

"Rebuilding" the early storms is a true challenge, with "not a lot to go on" other than geological evidence, anecdotal information and the old ship's logs and diaries.

One member of the multi-hazards team is Cary Mock at the University of South Carolina, who is a "paleoclimatologist" studying the ancient evidence of storms. Another is California state meteorologist Marty Ralph, who coined the term "atmospheric river."

Other entities involved include the National Oceanographic and Atmospheric Administration in Boulder, Colo.; the National Weather Service California unit; and other USGS people, Cox said.

One finding of the researchers is that "we had no good way of categorizing our storms," in the way that wind-velocities are categorized, or earthquakes measured.

"It's not about wind or inundation; it's about precipitation," he said. One comparison of precipitation in major storms indicated that Sacramento and Los Angeles areas have the largest precipitation concentrations of anywhere in the nation.

Such a major storm "would be a catastrophe if we are taken by surprise" and are unprepared.

By exploring the question of "What does the Big One mean?" the multi-hazards group could help California communities, counties and state and federal agencies be better prepared when one does hit.

Cox joined the USGS in 1994, surveying the High Plains Aquifer in Nebraska and helping to create the Groundwater Guardian international collaboration and the Groundwater Foundation. He later was chief of communications at USGS' Water Science Center, where he coordinated the Lake Tahoe Presidential Forum and the bathymetric mapping of Lake Tahoe.

He also helped coordinate the National Oceans Conference, also a presidential forum designed to raise awareness and develop international partnerships to tackle ocean issues. He served as the USGS' Western publishing manager. Cox and his wife, Kristin, a middle-school math and science teacher in El Dorado Hills, Calif., reside in Sacramento with their five daughters.

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