Folsom Dam - Flood Risk

Flood Risk

During a severe storm in December 1964, the inflow into Folsom Lake reached a record high of 280,000 cu ft (7,900 m3) per second, with a river release of 115,000 cu ft (3,300 m3) per second. This exceeded the downriver levee capacity by 15,000 cu ft (420 m3) per second. In 1986, nearly 500,000 people faced the possibility of flooding when engineers at Folsom Dam were forced to open the spillway gates after heavy rains.

The Bureau of Reclamation's Safety of Dams Program determined the risk of flooding in the Sacramento area made it one of the most at-risk communities in the United States.

Two projects to increase flood protection are currently underway. The first will raise the surrounding dikes by 7 feet (2.1 m) to increase flood protection. The second, a new spillway, is designed to handle the runoff from large storms and snowmelt floods that might cause damage in the region. The new spillway is built with gates 50 ft (15 m) lower than the existing spillway, allowing for more efficient evacuation of reservoir storage before flooding events.