The threat of the Oroville dam break occurred after protracted heavy rains in the area. According to USA Today, the state government will evacuate approximately 180 thousand people to safe zone.

In the photo: a bird's eye view of the Oroville dam, California.

After the rains in the area of one of the highest dams in the United States, the experts found that the dam's system of emergency spillway is faulty and the soil is eroded.

The representatives of the US Department of Water Resources said that the water level in the dam is on the warning mark.

Authorities issued the evacuation order on Sunday, saying that a crumbling emergency spillway on Lake Oroville Dam in north California could give way and unleash floodwaters onto rural communities along the Feather River.

In the photo: a huge gouge, formed on the dam's main spillway after heavy rains.

The state water resources department said crews using helicopters would drop rocks to fill a huge gouge.

At 770 feet (230 meters) high, the structure, built between 1962 and 1968, is the tallest U.S. dam. This evacuation was the first for the 50-year history of the dam.