Wednesday, December 15, 2021
On February 12, 2017, erosion at the tallest dam in the United States forced 188,000 people below Lake Oroville to evacuate with almost no notice.
On this day in 2017, officials ordered 188,000 people in three California counties to leave immediately. Five days earlier, crews had found a crater 250 feet wide in the main spillway of Oroville Dam, the tallest dam in the country. With the main chute damaged and an atmospheric river still feeding the reservoir, water spilled over the emergency weir for the first time in the dam's history and began cutting into the hillside underneath it.
The evacuation order came in the afternoon and gave families roughly an hour. Highways out of Oroville, Yuba City and Marysville jammed within minutes. The dam held, the reservoir was drawn down, and residents were allowed home after two days, but the repair bill reached about a billion dollars.
What makes Oroville worth remembering is that the sky was not the threat. The reservoir was doing its job and the concrete underneath it was not, and the warning arrived as a knock rather than a forecast. Anyone living below a dam, a levee or a hillside benefits from flood readiness that assumes an hour of notice, which is exactly the window a packed bug out bag is built for.
