With rising water levels on the Mississippi River, the U.S. Army Corps of Engineers announced it would open the Bonnet Carre' spillway on Wednesday. 

It will be the 13th flooding of the spillway and the first time since the concrete diversion structure was built in 1931 that it was used two years in a row. The Bonnet Carre' also was opened in 2016 — meaning it will have been opened three times in four years.

The spillway will have 38 of its bays opened this week, and it expected to be open for at least a month. As many as 200 bays could be opened at its peak usage. 

The spillway is opened when the water flow in the Mississippi reaches 1.25 million cubic feet per second in front of the structure 23 miles west of New Orleans. The levee system downstream of the Bonnet Carre' and past New Orleans isn't designed to handle water flow of more than 1.25 million cubic feet per second.

Ricky Boyett, a spokesman for the Corps' New Orleans district, said last week that continued rain in the Mississippi and Ohio river valleys has made water levels higher than normal for February.

More typically, the spillway has been opened during the traditional spring time high water between late March and May. But in recent years, the spillway has been opened early, including in March last year and in January 2016.

"It's becoming more and more frequent to have higher water earlier," Boyett said.

Located in St. Charles Parish near Norco, the concrete Bonnet Carre' control structure has 350 bays with 7,000 wooden needles that largely hold back river water until removed.


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Once opened, the bays allow river water to flow across a 7-mile stretch of land into Lake Pontchartrain and away from the lower river's channel. The overland section of the spillway has guide levees that run between the diversion structure on the river and the lake. They contain and route the river water.

Information from The Advocate's David Mitchell was used in this report.

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