TODAY: Corps to operate Bonnet Carré Spillway

Published May 10, 2019

TODAY: Corps to operate Bonnet Carré Spillway

NEW ORLEANS – Based on changes to the current and forecasted conditions the U.S. Army Corps of Engineers will operate the Bonnet Carré Spillway today as early as 1 p.m.

May 9 the Corps recommended operating the Bonnet Carré Spillway to the Mississippi Valley Division Commanding General with a tentative date of May 14. Regional rainfall caused the Mississippi River to rise 6 inches in the past 24 hours with more rain expected through the weekend. These rains could elevate the Mississippi River above 17 feet with a peak as high as 17.5 feet at the Carrollton Gage. In an abundance of caution the operation date is being moved forward to ensure the safe passage of this high water by limiting the elevations downriver of the spillway.

Operation of the structure will relieve pressure on main levees, maintain river stages, and regulate the flow downriver from the spillway. The decision to open Bonnet Carré was issued by Maj. Gen. Richard G. Kaiser commander of the Mississippi Valley Division in Vicksburg, Miss. This will be the 14 operation of the structure since 1937 and the first time it has been opened twice during the same high water event.

Media and the general public are allowed to view the spillway opening from the Project Office, located at 16302 River Road in Norco, Louisiana. Please note drones, and other unmanned aerial systems, are not permitted for flight during the opening.

Environmental, hydrologic, structural, and navigational considerations all bear on the decision to open Bonnet Carré.  Other factors that affect the decision are the overall condition of the levees and the ability of the river to pass flows, and the effects high water and river currents may have on vessels navigating the river. The Corps has a detailed environmental monitoring plan in place that will assess water quality, dissolved oxygen, sedimentation, recreation, and natural resources such as the pallid sturgeon, both within the spillway as well as Lake Pontchartrain.

About the Bonnet Carré Spillway

The Bonnet Carré Spillway, located 28 miles above New Orleans, is a vital element of the multi-state Mississippi River and Tributaries (MR&T) system, which uses a variety of features to provide flood risk reduction to the alluvial Mississippi Valley from Cape Girardeau, MO to Head of Passes, LA. Located on the east bank in St. Charles Parish, it can divert a portion of the river's floodwaters via Lake Pontchartrain into the Gulf of Mexico, thus allowing high water to bypass New Orleans and other nearby river communities. The structure has a design capacity of 250,000 cfs, the equivalent of roughly 1,870,000 gallons per second.

The Bonnet Carré structure consists of a control structure and a floodway. The control structure is a concrete weir that parallels the river for a mile and a half.  It consists of 350 gated bays, each holding 20 timber "needles," for a total of 7,000 needles. When needles are removed, river water flows into the floodway and is conveyed nearly six miles between guide levees to the lake. Operation of the structure is relatively simple. Two cranes, moving on tracks atop the structure, lift timbers from their vertical position in the weir and set them horizontally across the top of the structure to allow river water into the spillway.


Matt Roe

Release no. 19-017