Floods

All eyes on eroding dam spillway

All eyes were trained on the 770-foot-tall Oroville Dam on Monday, as a spillway of the nation’s tallest such barrier threatened to burst and unleash a massive wave of floodwaters on the California landscape below.

Nearly 200,000 people were under evacuation orders, many sitting in bumper-to-bumper traffic as they tried to escape the impending calamity.

A hole was first noticed in the emergency spillway of the dam on Feb. 7, and three days later it had grown to 300 feet wide by 500 feet long, according to SFGate.com.

SLIDESHOW: SPILLWAY ERODES IN CALIFORNIA

Helicopters were used on Sunday night to drop bags filled with rocks into the crevasse of the emergency spillway in an attempt to prevent more erosion, The Sacramento Bee reported.

The dam serves primarily for water supply, hydroelectricity generation and, ironically, flood control. It controls Lake Oroville, which is the second-largest man-made lake in California, located in the Sacramento Valley.

The Associated Press contributed to this report.