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DROWNING NEW ORLEANS |
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by Mark Fischetti Table of Contents:
The ocean has overtaken a now abandoned house on Isles Dernieres ("last islands" in French], an eroding barrier island that once protected the Mississippi Delta against the encroaching sea.
A major hurricane could swamp New Orleans under 20 feet of water, killing thousands. Human activities along the Mississippi River have dramatically increased the risk, and now only massive reengineering of southeastern Louisiana can save the city. THE BOXES are stacked eight feet high and line the walls of the large, windowless room. Inside them are new body bags, 10,000 in all. If a big, slow-moving hurricane crossed the Gulf of Mexico on the right track, it would drive a sea surge that would drown New Orleans under 20 feet of water. "As the water recedes," says Walter Maestri, a local emergency management director, "we expect to find a lot of dead bodies." New Orleans is a disaster waiting to happen. The city lies below sea level, in a bowl bordered by levees that fend off Lake Pontchartrain to the north and the Mississippi River to the south and west. And because of a damning confluence of factors, the city is sinking further, putting it at increasing flood risk after even minor storms. The low-lying Mississippi Delta, which buffers the city from the gulf, is also rapidly disappearing. A year from now another 25 to 30 square miles of delta marsh -- an area the size of Manhattan -- will have vanished. An acre disappears every 24 minutes. Each loss gives a storm surge a clearer path to wash over the delta and pour into the bowl, trapping one million people inside and another million in surrounding communities. Extensive evacuation would be impossible because the surging water would cut off the few escape routes. Scientists at Louisiana State University (L.S.U.), who have modeled hundreds of possible storm tracks on advanced computers, predict that more than 100,000 people could die. The body bags wouldn't go very far. A direct hit is inevitable. Large hurricanes come close every year. In 1965, Hurricane Betsy put parts of the city under eight feet of water. In 1992, monstrous Hurricane Andrew missed the city by only 100 miles. In 1998, Hurricane Georges veered east at the last moment but still caused billions of dollars of damage. At fault are natural processes that have been artificially accelerated by human tinkering -- levying rivers, draining wetlands, dredging channels and cutting canals through marshes [see map on pages 80 and 81]. Ironically, scientists and engineers say the only hope is more manipulation, although they don't necessarily agree on which proposed projects to pursue. Without intervention, experts at L.S.U. warn, the protective delta will be gone by 2090. The sunken city would sit directly on the sea -- at best a troubled Venice, at worst a modern-day Atlantis. As if the risk to human lives weren't enough, the potential drowning of New Orleans has serious economic and environmental consequences as well. Louisiana's coast produces one third of the country's seafood, one fifth of its oil, and one quarter of its natural gas. It harbors 40 percent of the nation's coastal wetlands and provides wintering grounds for 70 percent of its migratory waterfowl. Facilities on the Mississippi River, from New Orleans to Baton Rouge, constitute the nation's largest port. And the delta fuels a unique element of America's psyche; it is the wellspring of jazz and blues, the source of everything Cajun and Creole, and the home of Mardi Gras. Thus far, however, Washington has turned down appeals for substantial aid. Fixing the delta would serve as a valuable test case for the country and the world. Coastal marshes are disappearing along the eastern seaboard, the other Gulf Coast states, San Francisco Bay, and the Columbia River estuary for many of the same reasons besetting Louisiana. Parts of Houston are sinking faster than New Orleans. Major deltas around the globe -- from the Orinoco in Venezuela, to the Nile in Egypt, to the Mekong in Vietnam -- are in the same delicate state today that the Mississippi Delta was in 100 to 200 years ago. Lessons from New Orleans could help establish guidelines for safer development in these areas, and the state could export restoration technology worldwide. In Europe, the Rhine, Rhone and Po deltas are losing land. And if sea level rises substantially because of global warming in the next 100 years or so, numerous low-lying coastal cities such as New York would need to take protective measures similar to those proposed for Louisiana.
Seeing Is Believing SHEA PENLAND is among those best suited to explain the delta's blues. Now a geologist at the University of New Orleans, he spent 16 years at L.S.U.; does contract work for the U.S. Army Corps of Engineers, which builds the levees; sits on federal and state working groups implementing coastal restoration projects; and consults for the oil and gas industry. His greatest credential, however, is that he knows the local folk in every little bayou town, clump of swamp and spit of marsh up and down the disintegrating coast -- the people who experience its degradation every day. Penland, dressed in jeans and a polo shirt on a mid-May morning, is eager to get me into his worn red Ford F150 pickup truck so we can explore what's eating the 50 miles of wet landscape south of New Orleans. The Mississippi River built the delta plain that forms southeastern Louisiana over centuries by depositing vast quantities of sediment every year during spring floods. Although the drying sands and silts would compress under their own weight and sink some, the next flood would rebuild them. Since 1879, however, the Corps of Engineers, at Congress's behest, has progressively lined the river with levees to prevent floods from damaging towns and industry .The river is now shackled from northern Louisiana to the gulf, cutting off the sediment supply. As a result, the plain just subsides below the encroaching ocean. As the wetlands vanish, so does New Orleans's protection from the sea. A hurricane's storm surge can reach heights of more than 20 feet, but every four miles of marsh can absorb enough water to knock it down by one foot. The flat marsh right outside New Orleans is still a vibrant sponge, an ever changing mix of shallow freshwater, green marsh grasses and cypress swamp hung with Spanish moss. But as Penland and I reach the halfway point en route to the gulf, the sponge becomes seriously torn and waterlogged. Isolated roads on raised stone beds pass rusted trailer homes and former brothels along now flooded bayous; stands of naked, dead trees; and browned grasses and reaches of empty water. Down in Port Fourchon, where the tattered marsh finally gives way to open gulf, the subsidence and erosion are aggressive. The lone road exists only to service a collection of desolate corrugated buildings where oil and natural-gas pipelines converge from hundreds of offshore wellheads. Countless platforms form a gloomy steel forest rising from the sea. To bring in the goods, the fossil fuel companies have dredged hundreds of miles of navigation channels and pipeline canals throughout the coastal and interior marshes. Each cut removes land, and boat traffic and tides steadily erode the banks. The average U.S. beach erodes about two feet a year, Penland says, but Port Fourchon loses 40 to 50 feet a year -- the fastest rate in the country. The network of canals also gives saltwater easy access to interior marshes, raising their salinity and killing the grasses and bottomwood forests from the roots up. No vegetation is left to prevent wind and water from wearing the marshes away. In a study funded by the oil and gas industry, Penland documented that the industry has caused one third of the delta's land loss. Alligator Science THE DUET BROTHERS know first-hand how various factors accelerate land loss beyond natural subsidence. Toby and Danny, two of Penland's local pals along our route, live on a 50-foot beige barge complex anchored in the middle of 15 square miles of broken marsh, some 20 miles northwest of Port Fourchon. Their family leased the land from oil companies, for fishing and hunting, 16 years ago when it was merely wet. Now it lies under five to eight feet of water. They filter rain for drinking water, process their own sewage, catch the food they eat and make money hosting overnight fishing parties for sportsmen. A dozen wellheads dot the marsh where Toby picks us up by boat. Heading out to the barge through one canal, he says, "I used to be able to spit to the mud on either side. Now they run big oil containers through here."
Cypress swamps south of New Orleans die from the roots up as saltwater intrudes. The swamps then erode, allowing the gulf waters to advance even farther inland. SINKING OUT OF SIGHT Human beings have dramatically increased the rate of land loss in southeastern Louisiana -- and made themselves more vulnerable to hurricanes -- by restricting certain natural processes and accelerating the delta's natural subsidence. Even now, vast portions of the region lie only a few feet above sea level, and another 60 acres disappear every day. At this rate, New Orleans will be exposed to the open sea by 2090.
LEVEES inhibit the river's natural ability to sustain marshes with sediment and freshwater during spring floods. Without this supply, marshes subside and erode, and ocean water moves inland. This intrusion raises the salinity of marsh waters, killing trees and grasses that would otherwise prevent erosion. SOLUTION: REBUILD MARSHES. Cut one or more channels through the river levee on its south side and build control gates that would allow freshwater and sediment to exit and wash down through select marshes toward the Gulf of Mexico.
Southeastern Louisiana is a valuable test case for disappearing coastal wetlands around the world.
Like any river, the mighty Mississippi changes course over time. Over the past 4,600 years it has built four distinct deltas by depositing vast quantities of sediment each year during spring floods.
Land loss is exacerbated by human-made levees that shackle the river from northern Louisiana on the Gulf of Mexico and cut off the supply of sediment to surrounding marshlands. Between 1932 and 1990, the delta lost more than 1,000 square miles of land. |
