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Mississippi River and Tributaries (MR&T) Project |
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Mississippi River and Tributaries (MR&T) Project
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The MR&T is a
comprehensive plan that uses a variety of levees, spillways, river
band stabilization, channel improvement, and veg etation
to keep the Mississippi river in control. The main aspect of
the MR&T being the spillways. A spillway is a feature used to
redirect the water of the Mississippi to a nearby lake, therefore
protecting the communities down river. The spillway that
protects New Orleans is the Bonnet Carre' spillway. The Bonnet
Carre' spillway is about 33 river miles north of New Orleans.
The Bonnet Carre' drains water from the Mississippi River into Lake
Pontchartrain, about six miles east.
This area was chosen for a number of reasons. The Bonnet
Carre' levee had a history of developing cracks in it. Once
the water would start flowing through the crack, it could not be
fixed until the water stopped. This sometimes lasted 6-7
months. Another reason was its location to Lake Pontchartrain.
The Bonnet Carre' spillway was revolutionary for its time. Basically, it was just a series of twenty-two gates that would open and close in time of floods. If a flood was coming, the gates would open and sort of grab the water and force it into the spillway. A new type of concrete was also invented for the Bonnet Carre' spillway. This new concrete could withstand 5,000 pounds of pressure per square inch. This is in comparison to an average of 2,500 to 3,000 pounds per square inch in the 1930's. There are also many advantages to the Bonnet Carre' spillway. The Bonnet Carre' allows the natural process of flooding in the six mile stretch between the Mississippi River and Lake Pontchartrain. This flooding that occurs about once every ten year (average amount of time between major flood) replenishes vital nutrients to the soil. During these flood times, about "9 million cubic years of sediment" is deposited is the spillway. These sediments provide soil to New Orleans, which is below sea level at some sites. There is also leakage during low flood years. This leakage was not planned, it allows fresh water into the spillway, stimulating the growth of many different species. |
