Rainstorm Creates Reservoir Impoundment Behind Sepulveda Dam

Sepulveda Dam, at the headwaters of the Los Angeles River, is the western-most of the U.S. Army Corps of Engineers’ dams operated by the Los Angeles District in the Los Angeles County Drainage Area flood control system.

Rainstorms create reservoir impoundment behind Sepulveda Dam.

The reservoir reached 680 feet in elevation Feb. 4. The rising reservoir water surface causes Burbank Boulevard to be closed to traffic.  The Corps’ Reservoir Operations Center has notified local law enforcement of the reservoir’s rising elevation.

The project collects local runoff from the uncontrolled drainage areas upstream and reduces the peak discharge into the channelized portion of the Los Angeles River, so the downstream channel has capacity to collect the local inflow from the San Fernando Valley.

The Corps’ Los Angeles District does extensive coordination with many partners to assist them in determining what safety measures to implement.

The project has eight outlets, four of them gated. Because the other four passages have no gates, Sepulveda Dam is not intended to “shut off” the flow to the LA River. The “standby” position of the gated passages is wide open.

Flow passes through Sepulveda Dam without much reduction until the inflow is great enough for the reservoir elevation to rise. Then, as the LA River channel downstream approaches its capacity, the Corps of Engineers reduces the discharge to provide relief to the LA River downstream.

Recreational facilities developed by the City of Los Angeles that are in the reservoir, such as parks and golf courses, are permissible because they are compatible with occasional inundation from reservoir impoundments.

Sepulveda Reservoir is intended to impound water, which is not the same as flooding. Flooding is when unplanned water causes damage to the man-made environment and its inhabitants.