Sediment Diversion: Assessing the Potential of the Mississippi River to Mitigate Land Loss

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2023
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To avoid floods, engineers built long levees along the Mississippi river that are now preventing the Mississippi from depositing sediment into the surrounding floodplain and bays, and instead is diverting the sediment into the deeper parts of the Gulf of Mexico. Because sediment is not creating new land along the Mississippi, the compounded effects of a manmade rise in sea levels and the natural subsidence process are causing Louisiana to sink. A proposal by the Army Corps of Engineers, recently approved by the Louisiana state government, aims to redirect the Mississippi river towards coastal Louisiana and use sediment within the river to rebuild the floodplain. We contribute an analysis of the volume of sediment within the Mississippi and the volume of sediment required to regain the land lost since 1932. Using discharge and concentration data from the USGS, we conclude that, although there is ample sediment in the Mississippi to compensate for annual land loss, if the project is implemented in 2030, there is not enough sediment to regain all land lost since 1932 by 2090. We also calculate that from the year of implementation, it will take approximately 245 years to regain 50% of land loss since 1932, assuming that 50% of the river is successfully diverted.

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