Part iii-d – Dam Failure

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Seven Oaks and Prado Dam

Seven Oaks Dam

The Seven Oaks Dam is a single-purpose flood control project constructed by the US Army Corps of Engineers, Los Angeles District. The project is located on the Santa Ana River in the upper Santa Ana Canyon about eight miles (13 km) northeast of the city of Redlands, in San Bernardino County. Authorization for the project is contained in the Water Resources Development Act of 1986. Construction was completed on November 15, 1999.

The project is planned to operate in tandem with Prado Dam, also located on the Santa Ana River 40.3 miles (64.9 km) downstream, to provide flood protection to Orange County. During the early part of each flood season, runoff will be stored behind the dam in order to build a debris pool to protect the outlet works. Small releases will be made on a continual basis in order to maintain the downstream water supply. During a flood, Seven Oaks Dam will store water destined for Prado Dam for as long as the reservoir pool at Prado Dam is rising. When the flood threat at Prado Dam has passed, Seven Oaks will begin to release its stored floodwater at a rate which does not exceed the downstream channel capacity. At the end of each flood season, the reservoir at Seven Oaks will be gradually drained and the Santa Ana River will flow through the project unhindered.


Table - Seven Oaks Physical Data

NGVD – National Geodetic Vertical Datum



Earth and Rock Fill

Embankment Volume

37,626,983 CY

28,767,893 CM

Crest Elevation

2610 feet NGVD

795.5 meters NGVD

Stream-bed elevation at dam centerline

2060 feet NGVD

627.9 meters NGVD

Maximum height above stream-bed

550 feet

167.6 meters

Crest Length

2980 feet

908.3 meters


5.6 feet

1.7 meters



Rock Cut with Flush Concrete Crest

Crest Elevation

2580 feet NGVD

786.4 meters NGVD

Crest Length

500 feet

152.4 meters

Elevation of Maximum Water Surface

2604.4 feet NGVD

793.8 meters NGVD

Main Outlet Works

Intake Tower

Elevation of Tower Deck

2302.0 feet NGVD

701.7 meters NGVD

High-level Intake Elevation

2265 feet NGVD

690.4 meters NGVD

Height of Tower

225.5 feet

68.7 meters

Diameter of Main Wet Well

36 feet

11 meters

Upstream Conduit

Flow Regime

Pressure Flow

Diameter of Conduit

18 feet

5.5 meters

Length of Conduit

1009 feet

307.5 meters

Elevation of Conduit Invert at Intake

2100 feet NGVD

640.1 meters NGVD

Gate Chamber


69 feet

21 meters

Number of Main Gate Passages


Height x Width of Main Gates

8.5 x 5 feet

2.59 x 1.52 meters

Number of Low Flow Gate Passages


Height x Width of Low Flow Gate

3.5 x 2 feet

1.07 x 0.61 meters

Downstream Conduit

Flow Regime

Open Channel Flow

Length of Conduit

578 feet

176.2 meters

Height x Width of Conduit

9 x 18 feet

2.74 x 5.49 meters

Exit Channel

Flow Regime

Open Channel Flow

Length of Channel

280 feet

85.3 meters

Height x Width of Channel

14 x 18 feet

4.27 x 5.49 meters

Elevation of End of Exit Channel

2050.3 feet NGVD

624.9 meters NGVD

Multilevel Withdrawal Structure

Elevation of top of structure

2275.4 feet NGVD

693.5 meters NGVD

Elevation of invert of wet well

2100 feet NGVD

640.1 meters NGVD

Diameter of Minimum Discharge Line

3.0 feet

0.91 meters

Minimum Discharge Fixed Cone Valve

14 inches

0.36 meters

Water Supply Fixed Cone Valve

8 inches

0.20 meters


Area at Spillway Crest

780 Acres

3,156,548 sm

Gross Storage at Spillway Crest

145,600 Acre-feet

179.6 MCM

Flood Control Allocation

113,600 Acre-feet

140.1 MCM

Sedimentation Allocation

32,000 Acre-feet

39.5 MCM

Reservoir Design Flood

Total Volume (4-day)

115,000 Acre-feet

141.8 MCM

Peak Inflow

85,000 cfs

2406.9 cms

Peak Outflow

7,000 cfs

198.2 cms

Recurrence Interval

350 years (based on volume)

Spillway Design Flood

Total Volume

356,000 Acre-feet

439.1 MCM

Peak Inflow

180,000 cfs

5097.0 cms

Peak Outflow

174,000 cfs

4927.1 cms

Prado Dam

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