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California's Levees Seen Vulnerable to Breach

A section of Highway 4 serves as a levee road in the Sacramento-San Joaquin River Delta.  Stephen Flynn says a breach in Sacramento's levees would compromise much of California's fresh water supply.
David McNew / Getty Images
A section of Highway 4 serves as a levee road in the Sacramento-San Joaquin River Delta. Stephen Flynn says a breach in Sacramento's levees would compromise much of California's fresh water supply.
Homes are constructed next to a levee that holds back the higher waters of the Sacramento River.
David McNew / Getty Images
Homes are constructed next to a levee that holds back the higher waters of the Sacramento River.

Has the United States learned from Hurricane Katrina? Stephen Flynn, a former Coast Guard commander and author of The Edge of Disaster, worries that the answer is 'No.'

Flynn says that California's vulnerable levee system is likely to break down in the event of an earthquake. A breach in these levees would cause flooding in highly populated areas and compromise two-thirds of California's fresh water supply.

Just outside of Sacramento, more than 50 islands in an estuary are protected by earthen levees. The levees hold off spring waters from the surrounding mountain ranges.

Over the course of 100 years, the islands have sunk to be 25 feet below the water surrounding them.

"It actually has been sinking at a pace of about three inches a year," says Flynn.

One hundred years ago, farmers built earthen levees to protect fertile farm land. At the time, the land was five to six feet above the surrounding water. But with increased farming, the land began to sink.

"Every year that they tilled the soil, it dropped," Flynn says, "And so now there are some places where you are 40 feet below the surrounding water."

Sacramento's growth has encouraged many people to move into areas that are vulnerable to flooding.

"Sacramento has become one of the biggest growth areas in our country," says Flynn. "And folks are packing up and moving essentially onto these flood plains, where the only thing that is protecting their homes are these earthen works that are falling apart."

Earthquake Risk

It is not only the individuals who live in the flood plains who rely on the earthen levees. Sacramento's levees also protect much of California's fresh water supply.

A major earthquake, Flynn predicts, would cause massive breaches allowing salt water from the San Francisco Bay to salinate two-thirds of California's water supply. The area, he says, is essentially sitting in a bowl.

"Not only is this water that's moving around the levees providing irrigation for the surrounding fields and communities, but in California it provides about one-third of all the water for Los Angeles County, all the water for San Francisco Bay and provides all the irrigation water for the central valley. You basically have to shut down the fresh water supply for the seventh largest economy in the world."

California passed a bond in November to begin the repair of these levees. Yet these efforts do not address the possibility of an earthquake scenario, which Flynn predicts is likely in the next 50 years.

Planning for the Future

Flynn is concerned that today, the United States is not learning lessons from past disasters.

"Every generation of Americans has had to live with the risks that Mother Nature presents or just the challenges of occupying this North American continent," he says.

Flynn cites the 1906 San Francisco earthquake and the 1871 Chicago fire as examples of times when the United States learned important lessons from great disasters. He worries that he does not see similar reform efforts today.

"What seems unique about the era we're living in is that when we have a disaster like Katrina, we go back to sort of business as usual," Flynn says. "We let people build just where they were building before. We pretend that this was just something that is a rare event, instead of an almost certain event over a period of time."

Copyright 2021 NPR. To see more, visit https://www.npr.org.