OROVILLE, Calif. (AP) -- Authorities in Yuba County are asking people living in the valley floor to evacuate.
The Yuba County Office of Emergency Services says people should take routes to the east, south, or west and avoid traveling north toward Oroville.
The California Department of Water Resources says it is releasing as much as 100,000 cubic feet per second from the main, heavily damaged spillway to try to drain the lake.
Department of Water Resources spokesman Kevin Dossey tells the Sacramento Bee the emergency spillway was rated to handle 250,000 cubic feet per second, but it began to show weakness Sunday at a small fraction of that. Flows through the spillway peaked at 12,600 cubic feet per second at 1 a.m. Sunday and were down to 8,000 cubic feet per second by midday.
Officials have ordered residents near the Oroville Dam in Northern California to evacuate the area, saying a "hazardous situation is developing" after an emergency spillway severely eroded.
The Butte County Sheriff's Office says the emergency spillway could fail within an hour unleashing uncontrolled flood waters from Lake Oroville.
The department says people in downstream areas need to leave the area immediately.
It says residents of Oroville, a town of 16,000 people, should head north toward Chico and that other cities should follow orders from their local law enforcement agencies.
Water began flowing over the emergency spillway at the dam on Saturday after for the first time in its nearly 50-year history after heavy rainfall.