Sepulveda Dam

Sepulveda Dam

Sepulveda Dam is a single purpose flood control project constructed and operated by the U.S. Army Corps of Engineers, Los Angeles District. Construction of the project was completed December 30, 1941. The project is located on the Los Angeles River in the City of Los Angeles at the junction of the San Diego (405) and Ventura (101) Freeways. Authorization for the project construction is contained in the Emergency Relief Appropriations Acts of 9 April 1935 and 8 April 1936, the Flood Control Act of 22 June 1936 (PL 74-738) as amended by the Acts of 15 May 1937 and 28 June 1938 (PL 75-761), plus the Flood Control Act of 18 August 1941 (PL 77-228).

Sepulveda Dam is the western-most of the Corps of Engineers projects 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 to 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" flow to the Los Angeles River.

The "stand-by" 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 Los Angeles 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 water from the Los Angeles River downstream.

Sepulveda Dam has automatic spillway gates. The gates are normally in a down position which leaves the spillway crest at elevation 700 feet (213.36 meters) NGVD. When the water surface in the reservoir reaches elevation 692.5 feet (211.07 meters) NGVD, the spillway gates begin to rise, eventually reaching an elevation of 710 feet (216.41 meters) NGVD. The gates reach this height when the water surface in the reservoir reaches elevation 699 feet (213.06 meters) NGVD. If the water level in the reservoir continues to rise, the gates will remain at their maximum height until the water surface in the reservoir reaches elevation 712 feet (217.02 meters) NGVD. 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 elevation 715 feet (217.93 meters) NGVD or above, the gates will be fully lowered to their down position at elevation 700 feet (213.36 meters) NGVD.

The capacity of the Los Angeles River downstream from Sepulveda Dam is approximately 17,000 cfs (481 cms).

The current water control manual for Sepulveda Dam was approved in May 1989.


Operational Objectives   Flood peak reduction Local flood management
Original Completion Date   December 1941  
Stream System    Los Angeles River LACDA
Drainage Area    152 mi2  
Significant Upstream Flood Control Facilities   none    
DSAC Rating   3    
 Elevation NGVD 1929 + 2.22 ft = NAVD 1988
  Streambed at dam   668.0 ft 670.2
  Spillway crest (drum gates raised)   710.0 ft 712.2
  Revised Spillway design surcharge level2   716.7 ft 718.9
  Top of dam   725.0 ft 727.2
  Spillway crest (drum gates raised)   1,348 acres  
  Revised Spillway design surcharge level2   1,715 acres  
  Top of dam   2,591 acres  
 Capacity1, Gross      
  Spillway crest (drum gates raised)   18,129 af  
  Revised Spillway design surcharge level2   28,713 af  
  Top of dam   46,764 af  
  Allowance for sediment (100-year)2   None af  
Dam Type: Earthfill    
  Height above original streambed   57 ft  
  Top length   15,440 ft  
  Top width   30 ft  
Spillway Type: Concrete Ogee w/ 7 hydrostatically operated, submersable drum gates
  Crest length, net   399 (7 gates - 57 ft each) ft  
  WSE when drum gates begin to raise   692.5 ft 694.7
  WSE when drum gates begin to lower   712.0 ft 714.2
  Revised PMF freeboard   8.3 ft  
  Number and size   4 - 6.0' W x 6.5' H ft  
  Entrance invert elevation   668.0 ft 670.2
  Gates - type Hydraulic Vertical Lift Slide Gates    
  Number and size   4 - 6.0' W x 6.5' H ft  
  Entrance invert elevation   668.0 ft 670.2
 Conduits   Number - Size    
    Ungated   4 - 6.0' W x 6.5' H ft  
    Gated   4 - 6.0' W x 9.0' H ft  
  length   40 ft  
  Maximum capacity at spillway crest4   15,300 ft  
  Downstream channel capacity3   16,900 ft  
Reservoir Design Flood ➜   Original4   Resived SPF2
  Duration (Inflow)   5 days 2
  Total volume   52,880 af 68,220
  Inflow peak   69,000 cfs 50,000
  Outflow peak5   7,100 cfs 41,300
  Maximum water surface elevation   710 (712.2 NAVD) ft 713.5 (715.7 NAVD)
Spillway Design Flood ➜   Original4   Resived PMF2
  Duration (Inflow)   1 days 3.5
  Total volume   70,380 af 163,200
  Inflow peak   179,000 cfs 114,000
  Outflow peak   108,500 cfs 99,300
  Maximum water surface elevation   717.6 (719.8 NAVD) ft 716.7 (718.9 NAVD)
Historic Maximums Date      
  Maximum water surface elevation (2-16-1980) 705.1 ft 707.3
  Maximum storage7 (66% full) (2-16-1980) 11,470 af  
  Maximum 1-hour inflow (2-16-1980) 58,970 cfs  
  Maximum outflow (2-16-1980) 15,320 cfs  
1. Based on November 2004 Survey
2. Interim Report on H & H Review of Design Features of Existing Dams for LACDA, June 1978
3. LACDA Feasibility Interim Report, Hydrology Technical Report, December 1991
4. Sepulveda Dam Analysis of Design, August 1939 Draft
5. Unimproved downstream channel capacity was 7,100 cfs when dam was constructed.
6. Trash racks removed below 687.5 ft in 1946
7. Based on December 1980 survey, computed Dec 1982.