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.
SEPULVEDA DAM AND RESERVOIR
LOS ANGELES, CALIFORNIA
PERTINENT DATA - FEBRUARY 2015
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
Reservoir:
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
Area1
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
Outlets6
Uncontrolled
Number and size
4 - 6.0' W x 6.5' H
ft
Entrance invert elevation
668.0
ft
670.2
Controlled
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.