Geologists call it subsidence. Swampers say the salt marsh trembles and floats where the toe of Louisiana slips toward Havana, bleeding soil from 31 states. Layers of compacted mud weigh down the butter-soft lowlands. Ponds become estuaries. Barrier islands erode, exposing beachfront. The shore migrates, and so does the mile-wide river that carved in its time five paths to the ocean.
Curling and coiling like a snake in a sandbox, the Mississippi giveth and taketh away. It fans alluvial silt, then leaps to a new location, building, destroying.
No dam or system of levees can hold that mudscape in motion. Yet hold we must. For the sake of 2.1 million Louisianans on 3.3 million acres of marshland. For the nation's largest fin and shell fishery. For nine ports, 3,000 miles of shipping channels, 16,000 miles of pipelines, 180,000 licensed saltwater sport fishermen, and a $4 billion a year tourist industry. For 70 percent of the winged commuters on the Great Mississippi Flyway. For 15 percent of America's oil and 20 percent of its natural gas.
Holding Louisiana has vexed the nation's pre-eminent builders since the U.S. Army Corps of Engineers first assumed control of the New Orleans levees in 1917. As Louisiana recedes, however, the agency confronts a conundrum beyond the dam-it, ditch-it tradition: how to let the world's third-ranking river approximate the rhythms of nature — to meander and spread its mud blanket across a collapsing delta, to nourish without disrupting navigation or risking a serious flood.
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