Posted: May 5, 2011 3:22 PM by WBRZ Staff
Updated: May 5, 2011 3:22 PM
Source: U.S. Army Corps of Engineers
NEW ORLEANS - Heavy rain in the Mississippi Valley and rising Mississippi River water stages and flow are prompting the U.S. Army Corps of Engineers to open the Bonnet Carré Spillway on Monday, May 9, 2011 to keep the volume of Mississippi River flows at New Orleans from exceeding 1.25 million cubic feet per second (cfs).
Opening procedures will begin at approximately 8 a.m.
Media and the general public are allowed to view the spillway opening at the Bonnet Carré Spillway Project Office, located at 16302 River Road in Norco, Louisiana.
The spillway may be open for an estimated two to four week period. Operation of the structure will relieve pressure on main line levees, lower river stages, and reduce the velocity of the river current from the spillway southward.
The decision to open Bonnet Carré is the responsibility of Mississippi River Commission President Maj. Gen. Michael J. Walsh, commander of the Corps' Mississippi Valley Division in Vicksburg, Miss.
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.
Many of these monitoring efforts have been in place prior to any spillway opening and additional efforts will begin when the spillway is opened.
All third party users and grantees should take immediate steps to remove their movable property and protect existing facilities and immovable property within the spillway.
In addition, all public access areas within the spillway, including the public boat launches, Lower Guide Levee Road, and the St. Charles Parish Recreation Area near U.S. Highway 61 will be closed beginning on Monday, May 9, 2011 until further notice.
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.