The decision to operate or "open" the Bonnet Carré Spillway is the responsibility of the Mississippi River Commission 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 Carré structure and floodway.

The decision to operate the Bonnet Carré Spillway is made when existing conditions, combined with predicted river stages and discharges, indicate that the mainline levees in New Orleans and other downstream communities will be subjected to unacceptable stress from high water. Included in the complex decision process are environmental considerations, as well as hydrologic, structural, navigational and legal factors.

Once the decision to open the Bonnet Carré 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.

The Corps of Engineers initiated surveys and preliminary investigations for the Bonnet Carré 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.

   After heavy rains in the Mississippi and Ohio River valleys increased river stages, the Corps opened the spillway on May 9, 2011.

Spillway Opening Pace 2011 vs. 2008

Spillway Opening Pace 2008 vs. 1997

After heavy rains in the Mississippi and Ohio River valleys increased river stages, the Corps opened the spillway on Jan. 10, 2016.

The Bonnet Carre Spillway was partially opened on Monday, Jan. 10, 2016 in order to keep the volume of the Mississippi River flows at New Orleans from exceeding 1.25 million cubic feet per second (cfs).