Diverting a river to create new land
NEW NEW ORLEANS: By diverting the Mississippi, researchers say new land could form, seen above inside the white semicircles. (Photo: American Geophysical Union, NASA World Wind)
That’s an important finding for the Mississippi Delta, which has been losing about 17 square miles of land to the sea each year since 1940.
Although the river’s water naturally carries sediment southward from Minnesota to the Gulf of Mexico, levees built below New Orleans in the early 20th century have upset the natural balance between soil loss and sediment deposition. As a result, the waters at the end of the river flow fast and deposit sediments over the continental platform, draining into the Gulf of Mexico.
Researchers say the loss of land could be stopped by making two cuts, on opposite sides of the river, in levees 93 miles downstream from New Orleans. That way, nearly half the river’s water would spill out through those cuts, depositing sediment on each side of the river channel. As a result, new land would be created, reversing the alarming trend that would see 45 percent of the area vanish into the sea if nothing changes.
Other scientists have proposed similar solutions in the past, but critics have their reservations. Some say dams in the upper Mississippi have reduced the water’s sediment content so much that it’s not possible to rebuild the delta. Others say restoration is not possible, given the current sinking rate of the delta and future sea-level rise.