The Atchafalaya and the Mississippi Rivers

By: Shannon Condran & Anthony Gale

It is always the rivers purpose to get to the Gulf by the shortest and steepest gradient. The Atchafalaya River has a steeper gradient than the Mississippi River. As more and more water flows into the Atchafalaya, the deeper it makes its bed. The difference in level will in turn cause the main branch of the Mississippi to dry out. New Orleans and Baton Rouge are dependent upon the river for industry, shipping, fishing, and survival. After people had recognized the problem, an Army Corp of Engineers was assembled to try to correct the problem. They constructed many levies and spillways to attempt to contain the river and prevent the Atchafalaya from taking over. They also blocked off many outlets on the Mississippi to increase the flow and dig a deeper bed. This will lead to higher water levels that require the levies to be reinforced and built even higher. In addition to the levies the constructed what is called Old River Control.


Prediction of the rivers left on their natural course.


Water level after regulation by Corp.


The first two graphs indicate that the amount of water in this system will increase going into the Atchafalaya and decrease into the Mississippi over time. Eventually the Atchafalaya will take all the water if left on its natural course. The second two graphs represent how the rivers behave after the Corp regulated them. The horizontal line, representing the amount of water in the Atchafalaya, can move up or down according to how much water the Corp lets go through. Once adjusted, the line "should" remain horizontal as indicated by the desired level. By closing places where small amounts of water escape the Mississippi, the core rose the level of the river. This resulted in levies needing to be built higher and higher, increasing destruction if a major flood occurred.

Many think it is still very possible that the Atchafalaya could take over. The force of the turbulent water alone causes damage to Old River Control. A large rainfall or large snowmelt could cause the structure to fail as well as huge barges that become detached, float down river, and slam into it. The Army Corp of Engineers must find ways to handle problems. The economical implications involved will ensure that the best effort is made.