Water flowing over emergency spillway at Lake Oroville

OROVILLE, Calif. — Officials say water has begun flowing over the emergency spillway at Oroville Dam in Northern California for the first time since it opened in 1968.

A spokesman for California's Department of Water Resources says water began flowing over the emergency spillway around 8 a.m. Saturday, days after the main spillway unexpectedly eroded.

Officials hoped to avoid using the emergency spillway, fearing it could cause trees to fall and leave debris cascading into water that rushes through the Feather River, into the Sacramento River and on to the San Francisco Bay. Crews prepared for several days, clearing trees and brush.

Earlier in the week, chunks of concrete flew off the nearly mile-long spillway, creating a 200-foot-long, 30-foot-deep hole. Engineers don't know what caused the cave-in, which is expected to keep growing until it reaches bedrock.

Officials say the dam itself is sound and there is no imminent threat to the public.

The 770-foot-tall dam at Lake Oroville is the tallest in the nation.