Research / Sea Grant News

Protecting water supplies from the next “Big One”

The unexplained failure of the Jones Tract levee in June 2004 exposed the vulnerability of delta levees. COURTESY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES

The unexplained failure of the Jones Tract levee in 2004 exposed the vulnerability of delta levees. California Department of Water Resources/Stanford News

California is earthquake country.

According to the U.S. Geological Survey, the likelihood of a magnitude-7 or larger earthquake in California in the next 30 years is 94 percent – it’s not “if” but “when.”

While people may fear for their homes, scientists say it’s the water from your tap that may be most at risk.

About two-thirds of all Californians – more than 20 million people – get at least some of their water from the Sacramento-San Joaquin River Delta. That water is protected and channelized by an 1,100-mile collection of aging earthen levees.

To help guide costly levee reinforcement projects, Emma Gatti, a Delta Science Fellow and post-doctoral researcher at Stanford University, is now working with the U.S. Geological Survey and California Department of Water Resources to figure out which levees are most likely to collapse.

The idea is to map the locations of underlying sediments—young river channel sands, soft clays and flood basin deposits—that are most likely to liquefy, fail or deform in response to seismic activity. The most vulnerable levees are those that have been built on top of these unstable layers.

“A very large part of the Delta is at high risk,” said Jack Boatwright, Northern California’s earthquake hazards coordinator at the U.S. Geological Survey in Menlo Park. “We feel the levees are relatively weak but it’s really hard to quantify and know where to begin.”

Gatti’s research may help managers find a starting place.

Read more about the 2012 Delta Science Fellowship projects.

Written by Christina S. Johnson,


NOAA’s California Sea Grant College Program is a statewide, multi-university program of marine research, extension services, and education activities administered by Scripps Institution of Oceanography at the University of California, San Diego. It is one of 33 Sea Grant programs and is part of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce. Visit our website ( to sign up for email news or follow us on Facebook or Twitter.


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