[LINK] "Mississippi River Mouth Must Be Abandoned to Save New Orleans from Next Hurricane Katrina"

[rfmcdonald]

Scientific American's Mark Fischetti reports that the only way to spare New Orleans possible overflooding is to abandon the Mississippi Delta, the long tail stretching into the Gulf of Mexico. This is unsurprising, but I wonder if this is at all politically viable.

[H]ow does one reengineer the entire Mississippi River delta—one of the largest in the world—on which New Orleans lies?

Three international engineering and design teams have reached a startling answer: leave the mouth of the Mississippi River to die. Let the badly failing wetlands there completely wither away, becoming open water, so that the upper parts of the delta closer to the city can be saved. The teams, winners of the Changing Course Design Competition, revealed their detailed plans on August 20. Graphics from each plan are below.

Scientists worldwide agree that the delta’s wetlands disintegrated because we humans built long levees—high, continuous ridges of earth covered by grass or rocks—along the entire length of the lower Mississippi River. The leveed river rims the southern boundary of New Orleans and continues another 40 serpentine miles until it reaches the gulf. The levees, erected almost exclusively by the U.S. Army Corps of Engineers, prevented regular floods from harming farms, industries and towns along the river’s course. However those floods also would have supplied the brackish marshes with massive quantities of silt and freshwater, which are necessary for their survival.

Silt carries nutrients that grasses and mangroves need to stay lush, and it provides new material to build up the soft substrate beneath those plants, which subsides naturally under its own weight. Incoming freshwater mixes with the delta's saltwater to create the reduced salinity required by the region's vegetation. This soup also prevents pure ocean water from intruding further inland, which kills grasses and trees from the roots up.

Instead, hundreds of miles of navigation channels, cut by the Corps for more than half a century through the wetlands have torn the wetlands apart from within. So have thousands more miles cut by industry during the same period to build and maintain oil and gas pipelines running in from the Gulf.