Introduction
Past Floods in the
Lower Mississippi Valley
The Great Flood of 1927
The MR&T Project
Spillway Site Selection
Design Advances
Spillway Operation
Spillway Operational Effects
Natural Resource Values
Environmental Values
Cultural Resource Values
Recreational Values
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Operation of the Spillway
The decision to operate or "open" the Bonnet Carre'
Spillway is the responsibility of the MRC president who has
broad jurisdiction over the entire MR&T Project. The
MRC president relies heavily on the recommendations of
the New Orleans district engineer who is responsible for the
actual operation of the Bonnet Carre' structure and
floodway. Included in the complex decision process are
environmental considerations, as well as hydrologic,
structural, navigational and legal factors. Essentially, the
decision to operate the Bonnet Carre' Spillway is made when
existing conditions, combined with predicted stages and
discharges, indicate that the mainline levees in New Orleans
and other downstream communities will be subjected to
unacceptable stress from high water.
| In opening the spillway, each timber is individually lifted and placed atop the structure. |
Once the decision to open the Bonnet Carre' structure has been made, actual operation of the structure is relatively simple. Two cranes, which move along tracks atop the structure, are used to individually lift each timber from the required number of bays. The timbers are raised from their vertical position across the weir opening (where together they serve as a dam against the high water) and are laid horizontally on top of the structure for later use in its closing. A complete opening of all 350 bays requires about 36 hours to lift the 7,000 wooden timbers in the structure. If a quicker opening of the structure is ever required, emergency procedures can release 20 timbers at once and reduce the opening time to three hours.
| Opening of the Bonnet Carre' Spillway on March 17, 1997. The spillway was operational from March 17 to April 18, 1997 -- operating at a maximum flow of 243,000 cfs. |
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The Corps of Engineers initiated surveys and preliminary investigations for the Bonnet Carre' Spillway in 1928. Construction of the spillway structure began in 1929 and was completed in 1931. The guide levees were completed in 1932, and highway and railroad crossings in 1936. The total project cost was $14.2 million.
Contact
Kathy Gibbs, CEMVN-PA
Chief, Public Affairs Office
New Orleans, LA
504-862-2201
Kathy.Gibbs@usace.army.mil
Updated May 18, 2005
