Since the days of Huey Long, Louisiana has shrunk by more than two thousand square miles. If Delaware or Rhode Island had lost that much territory, the U.S. would have only forty-nine states. Every hour and a half, Louisiana sheds another football field’s worth of land.
…Thousands of miles of levees, flood walls, and revetments have been erected to manage the Mississippi. As the Army Corps of Engineers once boasted, “We harnessed it, straightened it, regularized it, shackled it.” This vast system, built to keep southern Louisiana dry, is the very reason the region is disintegrating.
…Whenever it overtopped its banks—something it used to do virtually every spring—the river cast its sediment across the plain. Season after season, layer after layer, clay and sand and silt built up.
…Bienville went on to found New Orleans, in 1718, in spite of his cold, wet feet. The new city, called, in honor of its watery surroundings, L’Isle de la Nouvelle Orléans, was laid out where the land was highest. Counterintuitively, this was right up against the Mississippi. During floods, sand and other heavy particles tend to settle out of the water first, creating what are known as natural levees.
…By the seventeen-thirties, slave-built levees stretched along both banks of the river for nearly fifty miles.
…Had the river been left to its own devices, a super-wet spring like that of 2011 would have sent the Mississippi and its distributaries surging over their banks. The floodwaters would have wreaked havoc, but they would have spread tens of millions of tons of sand and clay across thousands of square miles of countryside. The new sediment would have formed a fresh layer of soil and, in this way, countered subsidence.
Thanks to the intervention of the engineers, there had been no spillover, no havoc, and hence no land-building. The future of southern Louisiana had, instead, washed out to sea.
..Since the close of the crevasse period, land loss to the south has brought the city some twenty miles closer to the Gulf. It’s been estimated that for every three miles a storm has to travel over land its surge is reduced by a foot.
…Since Billiot was a child, the island has shrunk from thirty-five square miles to half a square mile—a loss in area of more than ninety-eight percent.
The island is disappearing for all the usual reasons. It’s part of an ancient delta lobe whose soil is compacting. Sea levels are rising. In the early part of the twentieth century, it lost its main sources of fresh sediment to flood-control measures. Then came the oil industry, which dug canals through the wetlands. The canals pulled in salt water, and, as the salinity rose, the reeds and marsh grasses died. The die-off widened the channels, allowing in more salt water, causing more die-off and more widening.
…With each successive storm, another chunk of land was lost and more families left. In the early two-thousands, a ring of levees was erected around the remnants of Isle de Jean Charles. These turned the bayou where people had once fished and crabbed into a narrow, stagnant pond. Inside the levees, land loss slowed. Outside and along the road, it only got worse.
…The Isle de Jean Charles band had been able to live peacefully on the island only because it was too isolated and commercially irrelevant for anyone else to take an interest in. The band had had no say in the dredging of the oil channels or in the layout of the Morganza to the Gulf project. They’d been excluded from the efforts to control the Mississippi, and, now that new forms of control were being imposed to counter the effects of the old, they were being excluded from those, too.
……He was referring to Asian carp, which were brought over from China in the nineteen-sixties and seventies. The fish, which had been imported to provide algae control, escaped from hatcheries during flood season and found their way into the Mississippi, and from there into virtually all of the river’s major tributaries. In some stretches of the Illinois River, Asian carp now make up ninety per cent of the fish stock by weight. Like the dissolution of the Louisiana coast, the carpification of the Mississippi basin is a man-made natural disaster.
…As the flow on the Atchafalaya increased, it widened and deepened.
In the ordinary course of events, the Atchafalaya would have kept widening and deepening until, eventually, it captured the lower Mississippi entirely. This would have left New Orleans low and dry and rendered the industries that had grown up along the river—the refineries, the grain elevators, the container ports, and the petrochemical plants—essentially worthless. Such an eventuality was thought to be unthinkable, and so, in the nineteen-fifties, the Corps stepped in. It dammed the former meander, known as Old River, and dug two huge, gated channels. The river’s choice would now be dictated for it, its flow maintained as if it were forever the Eisenhower era.
…At around 7:45 a.m., the levees on the Industrial Canal failed, sending a twenty-foot-high wall of water crashing through the Lower Ninth Ward. At least six dozen people in the predominantly African-American neighborhood were killed. Water was also surging into Lake Pontchartrain. As the hurricane pushed inland, this water was forced south, out of the lake and into the city’s drainage canals. The effect was like emptying a swimming pool into a living room. Soon the flood walls on the Seventeenth Street and London Avenue Canals gave way. By the next day, eighty per cent of the bowl was underwater.
…All sorts of radical ideas were put forward, and then shelved. Retreat might make geophysical sense; politically, it was a non-starter. And so the Corps was charged, yet again, with reinforcing the levees—in this case, against storm surges coming from the Gulf. South of the city, the Corps erected the world’s largest pumping station, part of a $1.1-billion structure called the West Closure Complex. To the east, it constructed the Lake Borgne Surge Barrier, a concrete wall nearly two miles long and five and a half feet thick, which cost $1.3 billion. The Corps plugged the Mississippi River Gulf Outlet with a nine-hundred-and-fifty-foot-wide rock dam and installed massive gates and pumps between the drainage canals and Lake Pontchartrain. The pumps at the foot of the Seventeenth Street Canal were designed to move twelve thousand cubic feet of water per second, a flow greater than the Tiber’s.
…Today, there are twenty-four stations, which together operate a hundred and twenty pumps. During a storm, rain is funnelled into a Venice’s worth of canals. Then it’s channelled into Lake Pontchartrain. Without this system, large swaths of the city would quickly become uninhabitable.
But New Orleans’s world-class drainage system, like its world-class levee system, is a sort of Trojan solution. Since marshy soils compact by de-watering, pumping water out of the ground exacerbates the very problem that needs to be solved. The more water that’s pumped, the faster the city sinks. And, the more it sinks, the more pumping is required.
…BA-39 had proved, not that further proof was really necessary, what enough pipes and pumps and diesel fuel can accomplish. Nearly a million cubic yards of sediment had made the five-mile journey, resulting in the creation—or, to be more accurate, the re-creation—of a hundred and eighty-six paludal acres. Here were all the benefits of flooding without the messy side effects: drowned citrus groves, drowned people, cows hanging from the trees. “We took centuries of land-building and we did it in a year,” Simoneaux observed. The bill for the project had been six million dollars, which, I calculated, meant that the acre we were standing on had cost about thirty thousand dollars.
…To match the pace of land loss, the state would have to churn out a hundred and eighty-six acres every nine days. Meanwhile, the artificial marsh had already begun to de-water and subside.
…The agency’s master plan calls for punching eight giant holes through the levees on the Mississippi and two more through those on its main distributary, the Atchafalaya. The openings will be gated and channelized, and the channels will themselves be leveed.
…Currently, the bill for the project is estimated at $1.4 billion. The next diversion in line, the Mid-Breton, which is planned for the east bank of Plaquemines, is priced at eight hundred million dollars. Financing for both diversions is supposed to come out of the settlement fund from the BP oil spill, which, in 2010, spewed more than three million barrels of oil into the Gulf, fouling the coast from Texas to Florida.
…Once the structure was completed, Barth explained, the gates would be opened when the river was at flood stage and carrying the most sand. After a few years, enough sediment would be deposited in Barataria Bay that terra semi-firma would start to form. The diversion would be powered by the river itself, instead of by pumps, and, in contrast with projects like BA-39, it would continue to deliver sediment year after year.
…“Sea level will continue to rise,” he said. The diversions planned for Plaquemines would add some land back to the marshes south of the city, and so, too, would more conventional dredging projects, like BA-39. “But I think the areas that don’t get restored will flood more and more frequently. There will be continued wetland loss.” The city once known as L’Isle de la Nouvelle Orléans would, in coming years, Kolker predicted, “look more and more like an island.”
Louisiana’s Disappearing Coast | The New Yorker