Last week a pair of geologists, at the University of Texas, Austin, proposed diverting the Mississippi and its sediment to Breton Sound on the east and Barataria Bay to the west in order to build new deltas in each body of water.
They would make the diversions about ninety miles south of New Orleans, my guess near Grand Bayou on the west, where the Mississippi levee runs, and Bohemia on the east, where the Mississippi River levee ends.
Like other who have proposed Mississippi River diversions to build land in Louisiana, they have looked at the landbuilding that is going on at the mouth of the Atchafalaya River and the Wax Lake Outlet from the Atchafalaya Basin. Since the completion of the Old River Control Structure in 1962, the Atchafalaya has funneled off 1/3 of the Mississippi water and sediment at Old River, about 200 miles north of New Orleans. The Atchafalaya also carries all of the Red River and its sediment to the Gulf of Mexico, where it is building new land. Last summer the New Orleans District of the Corps of Engineers announced it would study changing the ratio of Mississippi to the Atchafalaya with an eye to diverting more water and sediment to the Atchafalaya.
It should be noted that the Corps built the Old River Control Structure to keep the Mississippi from diverting to the Atchafalaya on its own in its effort to find a shorter, steeper route to the Gulf of Mexico.
All of this runs in the face of a paper published four months ago by a pair of geologists from Louisiana State University, stating that there is not enough sediment in the Mississippi to rebuild the Louisiana Coast. It’s all trapped behind dams in the Mississippi River basin, dams designed sometimes to retain floodwater in the uplands until the Mississippi and its tributaries could handle them, and built sometimes because the Corps of Engineers could and Congress approved.
Carl Pope, Executiver Director of the Sierra Club, put all this in perspective in an article at the Huffington Post. He came away from the Ecumenical Patriarch’s Eighth Religion, Science and the Environment Symposium with his own take on the state of the Mississippi River, the Missouri, the Atchafalaya, the Louisiana Coast, and New Orleans: they are all of a piece. The only way we are going to save the Louisiana Coast and New Orleans is to release the sediment, trapped behind dams on the Missouri, which supplied 60% of the mud to the Mississippi in 1900, and allow it to flow down the Mississippi/Atchafalaya and build land along the Louisiana Coast. This sediment is needed to keep up with the rise in sea level, which will come as Arctic ice melts.
To get the sediment to the coastal wetlands, something will have to be done about the levees that keep the Mississippi spilling over into the Louisiana parishes south of New Orleans. And, the river needs more room to flood north of New Orleans, where it is hemmed between levees–that protect cotton, corn, and soybeans–clear to the mouth of the Missouri River and above, where the Flood of 2008 breached agricultural levees in northern Illinois and farmers want a 500-year levee to protect their fields. New Orleans may get a 100-year levee someday.
Copyright © Quinta Scott, 2009, All Rights Reserved
Filed under: Atchafalaya River, Climate Change, Ecosystem, Flood of 2008, Infrastructure, Levees, Louisiana Coast, Mississippi River, Missouri River | Tagged: Louisiana Coast, Mississippi River, Missouri River, New Orleans, Old River Control Structure, Photography, Sierra Club |