A civil engineering professor at Mississippi State University (MSU) says that California’s ongoing drought could lead to “catastrophic failure” of parts of the state’s levee systems, and points to the need to invest in technologies to reduce their vulnerability.

Levee system near Bombay Beach in California. Source: wikimedia.orgCurrently, more than 21,000 kilometers of earthen levees deliver about two-thirds of potable water to more than 23 million Californians, and protect more than $47 billion worth of homes and businesses from flooding.

“An improved understanding of the resilience of critical infrastructure under a changing climate indisputably involves many authoritative and complex technical aspects,” says Farshid Vahedifard, who offered his findings in an article in the journal Science. “It also requires close collaboration between decision makers, engineers and scientists from various fields including climate science, social science, economics and disaster science. Community engagement and public risk education also are key to enhancing the resilience of infrastructure to climate change.”

Drought conditions—and particularly drought followed by heavy rainfall and flooding—may cause failures in California’s levee systems similar to those seen in 2008 along river banks of the Murray River at the peak of Australia’s Millennium Drought.

An MSU press release quotes Vahedifard as saying that little information has been published on the effect of drought on the performance of critical infrastructures. He says that the National Levee Database shows that around 10% of U.S. levees are rated as “acceptable,” with the rest being rated as “minimally acceptable” or “unacceptable.”

In California, many levee systems are currently rated as “high hazard,” meaning they are in serious danger of failing during an earthquake or flood event. This indicates that the resilience of these levee systems is a major concern without even considering the effects of the ongoing extreme drought, he says. Prolonged droughts threaten the stability of levee systems by inducing soil cracking, increased water seepage through soil, soil strength reduction, soil organic carbon decomposition, land subsidence and erosion.

“When you have a marginal system, then you just need the last straw to create a failure,” Vahedifard says.

MSU notes that he began research related to climate change and its impact on critical infrastructure with his colleague Agha Kouchak, a hydrologist, in 2013. They hypothesized that California’s current extreme drought will accelerate the ongoing land subsidence—or sinking. Recently, NASA’s Jet Propulsion Laboratory at the California Institute of Technology published a report that shows the Central Valley is undergoing subsidence of as much as two inches per month in some locations.

“This is exactly what we predicted, that this drought would lead to increased land subsidence,” Vahedifard says. The danger, he says, is that it increases the risk of water rising over the top of levees.

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