California’s 1,500 dams are regularly inspected and most have been safe for generations. Before last year’s Oroville Dam spillway crisis, the last dam disaster was the deadly 1928 Saint Francis Dam failure in Southern California. But the scale and drama of the Oroville crisis jolted the state into action, resulting in a stream of safety reviews, forensic analyses, and policy changes.

Within weeks of Oroville’s spillway incident, Governor Brown announced a 4-point plan to bolster dam safety and flood protection. And with the enactment of Senate Bill 92, a new dam safety regime has strengthened the state’s existing system.

We asked two experts about the lessons of Oroville for dam safety in California: Jeff Mount, a senior fellow at the PPIC Water Policy Center and an expert in hydrology and geology; and Jay Lund, director of the Center for Watershed Sciences at UC Davis, a member of the National Academy of Engineering, and an adjunct fellow at PPIC.

“First, we have to do a more complete job of assessing infrastructure,” said Lund. “We need to look for potential cascades of failures, which is what happened at Oroville. And we need to look at all of the outlet structures, which are essentially a dam’s safety valves.”

He noted that all federally regulated dams are subject to safety analysis every seven years, “yet they didn’t pick up the problems of Oroville. The lessons here are that you can never stop worrying about infrastructure and that we have to be prepared for things to fail.”

Mount seconded the need to stay vigilant, noting, “Water has a way of finding weaknesses in planning, design, and maintenance. If you miss something, eventually water will find a way to tell you so.”

Another new dam safety bill, Assembly Bill 1270, requires the state to consult with independent experts to update dam safety practices every 10 years. Lund said that will encourage the use of new kinds of technologies and practices. “But I think more important than the law itself is the culture of the people in charge of dams and dam safety, and whether they’re given the right resources and the mission to do more thorough assessments of old problems lurking in these structures.”

Mount noted that climate change is a complicating factor. “The inspections and upgrades are a good start,” he said. “But many of our dams―including Oroville―were designed more than 50 years ago. We need to evaluate how to operate them under changing hydrologic conditions.”

He added that many large dams try to fulfill multiple, conflicting objectives. “For example, a flood manager wants an empty reservoir during flood season while a water supply manager wants to fill the reservoir as much as possible. We’ll need to take a second look at how we manage dams for competing objectives and will likely face some tough trade-offs.”

Oroville also raises the question of how to pay for dam safety over the long term. “The Oroville episode will probably end up costing slightly less than $1 billion,” Lund said. “At 5% interest, that’s $50 million a year. A $50 million annual flood safety program might have avoided this. There is probably a good financial argument to increase spending on maintenance and inspection of major infrastructure.”