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Catching a glimpse as Mighty Miss diverts path

By Tom Junod, NBC News Producer

NEW ORLEANS, La. – New Orleans may be a city vulnerable to flooding, as Hurricane Katrina and the ensuing levee failures proved, but the Mississippi River isn't likely to be the cause. That's because there's an elaborate series of features and structures that protect the city. 

One of the most important is the Bonnet Carré Spillway, about 28 miles upriver from New Orleans. When the river starts running high and fast, as it is now, the Army Corps of Engineers can open up the spillway gates before things get too dicey downstream.  

A portion of the river's flow is diverted down a six-mile channel and into Lake Pontchartrain, where it eventually flows out into the Gulf of Mexico. The spillway can siphon off up to 1,870,000 gallons of water per second. It's like a big valve releasing built-up pressure.  

Bonnet Carré Spillway
Tom Junod / NBC News
The Bonnet Carré Spillway, about 28 miles upriver from New Orleans, is opened to prevent flooding.

The spillway hasn't been used often. This is just the ninth time since 1937 that it's been opened, and the first time in 11 years. 

Festive scene

It's quite an event when the spillway is opened and this weekend brought out scores of onlookers who lined the levees for a glimpse of the Mighty Mississippi bending to the will of man. 

Crowds watch opening of Bonnet Carré Spillway.
Tom Junod/ NBC News
Onlookers line the levees to catch a look as Mighty Mississippi bends its path.

The atmosphere was festive as families with young kids and babies in strollers crowded in to catch a glimpse along with kite-flyers and scores of fisherman taking advantage of a new place to cast their lines. 

Fishing in Bonnet Carré Spillway
Tom Junod / NBC News
Some young boys take advantage of the new fishing hole created by the opening of the spillway.

The Army Corps of Engineers expects the spillway to be open from two to four weeks. Once the danger of flooding downriver has passed they'll close it and the Mississippi will once again be confined to its normal path.

The Army Corps' website offers a detailed explanation of how the Bonnet Carré Spillway works.