More than 100,000 people fled their homes in northern California on Sunday as an emergency spillway next to America's tallest dam threatened to collapse and unleash what authorities called a catastrophic amount of water along the Feather River. While the evacuation took place, emergency repairs were performed on the spillway at the 770-foot Oroville Dam, with helicopters dropping rock-filled containers, the San Francisco Chronicle reports. The cities of Oroville, Yuba City, and Marysville were among those under mandatory evacuation orders. Saturday, when a hole developed in the main spillway, was the first time the emergency spillway was used since the dam was completed in 1968. Authorities say the dam itself remains structurally sound, reports the Los Angeles Times.
Officials said Sunday night that the immediate danger was subsiding because the level of the man-made Lake Oroville had dropped below the level of the emergency spillway for the first time in more than 24 hours, the Sacramento Bee reports. But authorities warned that the danger of catastrophic flooding remains, with the main spillway still in danger of collapse because water was released so quickly along it to relieve pressure on the auxiliary spillway, causing further erosion. The AP reports that the evacuation order covered 188,000 people in Yuba, Sutter and Butte counties and that people were stuck in bumper-to-bumper traffic out of the area more than five hours after the order was issued.