During heavy rain in February 2017, concrete collapsed at California’s Oroville Dam, the tallest in the nation. Water pushed through the 3,000-foot-long spillway and drowned the adjacent hillside, eventually overtopping the emergency spillway.
Erosion undermined the dam and officials ordered the evacuation of more than 150,000 downstream residents amid fears of a catastrophic failure.
The worst-case scenario didn’t materialize. But the structure suffered over a billion dollars in damage, and California lawmakers within six months passed laws strengthening oversight and requiring owners of risky dams to post inundation maps showing the extent of potential flooding if a dam failed.
In state after state, the gears of policy start grinding after a crisis.
“That’s what happens when you have a significant dam event,” said Lori Spragens, executive director of the Association of State Dam Safety Officers.
The responses that follow major incidents often
