Brea Dam

Brea Dam, constructed, operated and maintained by the Corps of Engineers (COE), is a single purpose flood control project. The dam is located in the city of Fullerton just upstream of the fork of Brea Boulevard and Harbor Boulevard. Construction on the dam began in July 1940 and was completed in March 1942. Brea Dam, one of the units of the flood-control project for the San Gabriel River Basin and Orange County, California, was conceived under authorization of the Flood Control Act of 22 June 1936.

Brea Dam controls 22.0 square miles of drainage area of Brea Creek and its tributaries. Brea Creek generally flows southwesterly into the reservoir. Below the dam, the creek flows southward through the central business district of the city of Fullerton, where it turns westward to join Coyote Creek, a tributary of the San Gabriel river.

Brea Dam consists of : (1) an earthfilled embankment; (2) a reinforced concrete outlet works; (3) an ungated outlet; (4) a detached spillway; (5) saddle dike; and (6) reservoir.

The stand-by gate setting for the dam is currently 2 gates open at 3.5 feet. The regulation schedule at the dam during flood events is based on a combination of precipitation at the Brea Dam station during the preceding 30-minute period and current water surface elevation. Additionally, the downstream channel capacity must be monitored, and if need be, modify releases from the published schedule to prevent overtopping of the downstream channel.

The channel capacity immediately downstream of the dam is 2,000 cfs as provided by a rectangular reinforced concrete channel. For next three miles, the capacity increases to a 2,200 cfs to 3,000 cfs capacity rectangular reinforced concrete channel. In the next 2 miles of channel, the capacity expands to 11,000 cfs. For last mile, just upstream of the confluence with Coyote Creek, the capacity ranges from 3,500 cfs to 4,000 cfs.

The current water control manual for Brea Dam was approved in May 1990.


Operational Objectives   Flood Control    
Original Completion Date   March-1942 Authorized as part of SAR
Stream System    Brea Creek  LACDA, drains to San Gabriel River
Drainage Area    22 mi2  
Significant Upstream Flood Control Facilities3   None    
DSAC Rating   4 as of 2015  
 Elevation Local Datum +1.22 ft = NAVD 1988
  Original Streambed Elecation2   205.0 ft 206.2
  Intake Invert2   208.0 ft 209.2
  Spillway crest   279.0 ft 280.2
  Revised Spillway design surcharge level3   292.2 ft 293.4
  Top of dam4   295.0 ft 296.2
  Top of Prapet Wall 298.0 ft 299.2
  Spillway crest   163 acres  
  Spillway design surcharge level3   250 acres  
  Top of dam   273 acres  
 Capacity, Gross1      
  Spill way crest   3,888 af  
  Spill way design surcharge level3   6,568 af  
  Top of dam   7,300 af  
  Allowance for sediment (50-year)2   1,200 af  
Dam2 Type: Earthfill    
  Height above original streambed (not including parapet)   90 ft  
  Top length   1,765 ft  
  Top width   20 ft  
  Saddle Dike crest length   640 ft  
  Saddle Dike crest height   41 ft  
Spillway2 Type: Ungated, overflow concrete ogee
  Crest length   150 ft  
  Revised PMF available freeboard3   2.8 ft  
Outlets2 Type: Ungated, overflow concrete ogee
  Number and size   2 - 3.0' W x 2.5' H ft  
  Entrance invert elevation   251 ft 252.2
  Gate type   Electric Motor Vertical Lift    
  Number and size   2 - 5' W x 8' H ft  
  Entrance & Exit invert elevations   208 & 207 ft 209.2 & 208.2
  Number and size   2 - 5' W x 8' H ft  
  Length   484 ft  
  Maximum conduit capacity at spillway crest   3,790 cfs  
  Maximum schedule release   1,500 cfs  
  Length   484 cfs  
Reservoir Design Flood ➜   Original2   Resived SPP2
  Duration (Inflow)   5 days 2
  Total volume   9,440 af 8,260
  Inflow peak   8,300 cfs 8,000
  Outflow peak   1,330 cfs 5,400(6)
  Maximum water surface elevation   278.9 (280.1 NAVD) ft 283.3 (284.5 NAVD)
Spillway Design Flood ➜   Original2   Resived PMP2
  Duration (Inflow)   24 days 2
  Total volume   8,200 af 8,260
  Inflow peak   16,800 cfs 8,000
  Outflow peak   14,500 cfs 5,400(6)
  Maximum water surface elevation   287.7 (288.9 NAVD) ft 292.2 (293.4 NAVD)
Historic Maximums Date NGVD 1929   NAVD 1988
  Maximum water surface elevation 3/1/1983 252.0 ft 253.2 NAVD
  Maximum storage (27% full) 3/1/1983 10737 af  
  Maximum 1-hr Inflow 2/21/2005 2,964 cfs  
  Maximum release 3/1/1983 1,430 cfs  
1. Based on May 1994 (WSE 208-277) & June 1964 (WSE 277-295) Surveys
2. Brea Creek Improvement, Brea Dam Analysis of Design, February 1940
3. Interim Rpt, Review of Design Features of Existing Dams, H&H Review, Prado, Brea, Fullerton & Salinas Dam, November 1969
4. This is the top of the main embankment. There is a 3' high parapet wall built on the embankment in 1973 to provide adequate freeboard.
5. Capacity directly d/s is 2,200 cfs (LACDA Feasibility Interim Report, Hydrology Technical Report, December 1991) but is 2,000 cfs shortly thereafter (OCPW).
6. Revised SPF results in spillway flow under current operation plan. Increasing maximum scheduled release to 2,200 cfs avoids spillway flow.
7. Based on June 1964 survey (pre-1975 computation)