LOS ANGELES –Sepulveda Dam is the western-most of the Corps of Engineers’ dams operated by the Los Angeles District in the Los Angeles County Drainage Area (LACDA) flood control system. The purpose of the project is to collect flood runoff from the uncontrolled drainage areas upstream, store it temporarily, and release it into the Los Angeles River at a rate that does not exceed the downstream channel capacity. The project has eight outlet passages, of which only four have gates. Because the other four passages have no gates, Sepulveda Dam cannot “shut off” the flow to the LA River.
The “standby” position of the gated passages is wide open. During the initial stages of a flood event, Sepulveda Dam will release as much of the inflow as is physically possible. This minimizes the amount of stored water and the impact to facilities located within the basin. However, as the LA River channel downstream approaches its capacity, the Corps of Engineers begins to close the gates in the gated outlet passages. This results in more water stored in the reservoir, but prevents the escape of the water from the LA River downstream.
Sepulveda dam has automatic spillway gates. The gates are normally in the down position, which leaves the spillway crest at an elevation of 700 feet. When the water surface in the reservoir reaches an elevation of 692.5 feet, the spillway gates begin to rise, eventually reaching an elevation of 710 feet. The gates reach this height when the water surface in the reservoir reaches an elevation of 699 feet. If the water level in the reservoir continues to rise, the gates will remain at their maximum height until water surface in the reservoir reaches an elevation of 712 feet. At this point the gates will begin to lower, thus increasing the discharge capacity of the spillway. If the water surface in the reservoir reaches an elevation of 715 feet or higher, the gates will be fully lowered to their down position at an elevation of 700 feet.
The highest water surface elevation ever reached at Sepulveda Dam was 705.10 feet. The dam has never spilled! Water has always been released into the Los Angeles River through the outlet works at a rate that did not exceed the capacity of the downstream channel.
Facilities located within the reservoir basin, such as roads, parks and golf courses, have been allowed into the basin based upon their ability to withstand occasional inundation caused when water is temporarily stored in the reservoir.
Sepulveda Dam does not spill – it releases water down the Los Angeles River.
Sepulveda Basin does not flood – it holds/retains water, as it is designed to do.
Release no. 14-003