Breaux Act Newsflash - Bonnet Carre Spillway Opened on Thursday, April 10, 2008
***********************************************************************Corps to open Bonnet Carre Spillway
11:18 AM CDT on Thursday, April 10, 2008
The following is a statement released by the Corps of Engineers regarding
the Bonnet Carre Spillway being opened on Friday.
VICKSBURG, Miss. -- Heavy rain in the Mississippi Valley is prompting the
U.S. Army Corps of Engineers to open the Bonnet Carre Spillway on Friday,
April 11, 2008, for the first time in 11 years.
The Corps will open the spillway to keep the volume of Mississippi River
flows at New Orleans from exceeding 1.25 million cubic feet per second
(cfs), which current projections indicate will occur on April 11, 2008.
The spillway may be open for an estimated two to four week period, during
which time the Mississippi is expected to crest at about 17 feet at New
Orleans, without operation of the spillway. Operation of the structure
will relieve pressure on local levees, lower river stages, and reduce the
velocity of the river current from the spillway southward.
The decision to open Bonnet Carre is the responsibility of Mississippi
River Commission President Brig. Gen. Michael J. Walsh, commander of the
Corps' Mississippi Valley Division in Vicksburg, Miss.
Environmental, hydrologic, structural, navigational and legal
considerations all bear on the decision to open Bonnet Carre. Essentially,
the spillway is only operated when existing conditions, combined with
predicted discharges, reach the operational level as prescribed in the
approved Bonnet Carre Spillway Operations Manual and the Mississippi
Valley Division Operations Plan 2007-02 for Floods.
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,
including the risk of vessels losing control and colliding with levees.
Bonnet Carre, 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 protection to the alluvial
Mississippi Valley from Cape Girardeau, Mo., to Head of Passes. MR&T
features include levees and floodwalls to contain flood flows, floodways
(such as Bonnet Carre) to redirect high flows out of the Mississippi
River, reservoirs and pumping plants for flood control drainage, and
channel improvement and stabilization features to protect the levees and
improve navigation of the river.
Bonnet Carre is the southernmost floodway in the MR&T system. 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 Carre 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 aside. A complete opening of
all 350 bays is not planned at this time.
Bonnet Carre was first opened during the flood of 1937; since then it has
operated seven other times, during high water in 1945, 1950, 1973, 1975,
1979, 1983, and 1997. The flood of 1997 was the last time the spillway
was operated.
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[Edited 2008-04-11 -webmaster]