Emergency evacuations are being declared downstream from the Oroville Dam after erosion on the emergency spillway.

5:15 p.m.

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 dam on Saturday for the first time in its nearly 50-year history after heavy rainfall.