Thousands of people have fled endangered areas in Northern California after authorities warned that the emergency spillway of Oroville Dam could collapse. Recent rainfall has caused waters to rise at the structure.
Image: Reuters/M. Whittaker
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Authorities ordered the evacuation of low-lying areas of Oroville, Yuba and other towns downstream from Oroville Dam on Sunday, citing a "hazardous situation" at the tallest dam in the US. According to US Census data, over 160,000 people live in the area.
Image: DW
The dam's main spillway was severely damaged by erosion last week, prompting authorities to activate the emergency outlet. On Sunday, Butte County Sheriff's department said that the auxiliary spillway also suffered "severe" damage through its use.
"Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville," the sheriff's department said on social media, ordering the evacuation and adding "This is NOT A Drill. This is NOT A Drill. This is NOT A Drill."
After advising that the spillway was predicted to fail imminently, Butte County Sheriff Korey Honea said at an evening press conference that erosion was not progressing as rapidly as had been feared and the amount of water flowing over the spillway had dropped quickly.
Oroville dam itself was "sound" and structurally separate from the auxiliary spillway, a spokesperson for the California Department of Water Resources told a public TV channel in San Francisco.
The barrier is 770-feet (235 meters) high, making it 14 meters taller than the more famous Hoover Dam. Lake Oroville's water level has risen this winter due to heavy rain and snowfall, which came after years of drought. On Friday, water levels were reported to be around two meters from the top of the wall.
The structure is almost 50 years old and located upstream from the town of Oroville, which has 16,000 residents.
Evacuation centers were set up at a fairground in Chico, 20 miles northwest of Oroville.
Mass evacuation ordered below California's Oroville Dam
Authorities have ordered nearly 200,000 people in northern California to evacuate an area below a dam spillway that may collapse. A failure of the spillway at Lake Oroville Dam could unleash a massive flood.
Image: Getty Images/M.Ralston
Hole in main spillway
The dam's main spillway was damaged (pictured center), forcing authorities to use the emergency spillway on Saturday for the first time in the dam's 48-year-old history. Officials at first believed the emergency spillway had helped lower water levels in the lake, before they noticed erosion.
Image: Reuters/California Department of Water Resources/William Croyle
Lake overflow
A view of the Lake Oroville Dam (right) from a helicopter. Center-left is the damaged main spillway. The emergency spillway is to the far left.
Image: picture-alliance/AP Photo/Office of Assemblyman Brian Dahle/Josh F.W. Cook
Threat of collapse
The emergency spillway (top half of picture) suffered severe erosion that led authorities to believe it could collapse within hours. They then released more water from the main damaged spillway to "avert more erosion at the top of the auxiliary spillway." Water levels have since receded slightly.
Image: picture-alliance/AP Photo/California Department of Water Resources/A. Madrid
Large-scale evacuations
Evacuation orders were given to about 200,000 people in Oroville, Yuba County, Butte County and Marysville. Oroville was said to be eerily deserted on Sunday. Officials said a 9-meter-high (30-foot) flood wave could hit Oroville if the spillway structure collapsed.
Image: DW
Hillside erosion
A picture released by the California Department of Water Resources shows the the hole in the main damaged spillway and erosion to the hillside. "Once you have damage to a structure like that, it's catastrophic," acting Water Resources director Bill Croyle told
reporters. He emphasized, though, that "the integrity of the dam is not impacted" by the damaged spillway.
Image: Reuters/California Department of Water Resources/William Croyle
Leaving by night
Residents were ordered to leave areas down from the dam due to high water flows and the potential for a failure at a spillway.
Image: picture-alliance/AP Photo/P. Kitagaki Jr.
From droughts to floods
California has experienced years of drought and a water crisis. A picture from May, 2015, shows boats moored in an arm of Lake Oroville when the water level was less than 25-percent capacity.
