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Friday, Nov 27, 2009
As sediments slide down the continental slope and the river is prevented from building a proper lobe -- as the delta plain subsides and is not replenished -- erosion eats into the coastal marshes, and quantities of Louisiana steadily disappear. The net loss is over fifty square miles a year. In the middle of the nineteenth century, a fort was built about a thousand feet from a saltwater bay east of New Orleans. The fort is now collapsing into the bay. In a hundred years, Louisiana as a whole has decreased by a million acres. Plaquemines Parish is coming to pieces like old rotted cloth. A hundred years hence, there will in all likelihood be no Plaquemines Parish, no Terrebonne Parish. Such losses are being accelerated by access canals to the sites of oil and gas wells. After the canals are dredged, their width increases on its own, and they erode the region from the inside. A typical three-hundred-foot oil-and-gas canal will be six hundred feet wide in five years. There are in Louisiana ten thousand miles of canals. In the nineteen fifties, after Louisiana had been made nervous by the St. Lawrence Seaway, the Corps of Engineers built the Mississippi River-Gulf Outlet, a shipping canal that saves forty miles by traversing marsh country straight from New Orleans to the Gulf. The canal is known as Mr. Go, and shipping has largely ignored it. Mr. Go, having eroded laterally for twenty-five years, is as much as three times its original width. It has devastated twenty-four thousand acres of wetlands, replacing them with open water. A mile of marsh will reduce a coastal-storm-surge wave by about one inch. Where fifty miles of marsh are gone, fifty inches of additional water will inevitably surge. The Corps has been obliged to deal with this fact by completing the ring of levees around New Orleans, thus creating New Avignon, a walled medieval city accessed by an interstate that jumps over the walls.
"The coast is sinking out of sight," Oliver Houck [of Tulane University Law School's environmental program] has said. "We've reversed Mother Nature." Hurricanes greatly advance the coastal erosion process, tearing up landscape made weak by the confinement of the river. The threat of destruction from the south is even greater than the threat from the north.
I went to see Sherwood Gagliano one day -- an independent coastal geologist and regional planner who lives in Baton Rouge. "We must recognize that natural processes cannot be restored," he told me. "We can't put it back the way it was. The best we can do is try to get it back in balance, try to treat early symptoms. It's like treating cancer. You get in early, you may do something." Gagliano has urged that water be diverted to compensate for the nutrient starvation and sediment deprivation caused by the levees. In other words, open holes in the riverbank and allow water and sediment to build small deltas into disappearing parishes. "If we don't do these things, we're going to end up with a skeletal framework with levees around it -- a set of peninsulas to the Gulf," he said. "We will lose virtually all of our wetlands. The cost of maintaining protected areas will be very high. There will be no buffer between them and the coast."
Professor Kazmann, of LSU, seemed less hopeful. He said, "Attemps to save the coast are pretty much spitting in the ocean."
The Corps is not about to give up the battle, or so much as imagine impending defeat. "Deltas wax and wane," remarks Fred Chatry, in the pilothouse of the Mississippi. "You have to be continuously adjusting the system in consonance with changes that occur." Southern Louisiana may be a house of cards, but, as General Sands [of the Army Corps of Engineers] suggested, virtually no one would be living in it were it not for the Corps. There is no going back, as Gagliano says -- not without going away. And there will be no retreat without a struggle. The Army engineers did not pick this fight. When it started, they were still in France. The guide levees, ring levees, spillways, and floodways that dangle and swing from Old River are here because people, against odds, willed them to be here. Or, as the historian Albert Cowdrey expresses it in the introduction to "Land's End," the Corps' official narrative of its efforts in southern Louisiana, "Society required artifice to survive in a region where nature might reasonably have asked a few more eons to finish a work of creation that was incomplete."
Excerpt from "Atchafalaya" from "The Control of Nature" by John McPhee. Copyright ) 1989 John McPhee. Reprinted by permission of Farrar, Straus and Giroux, LLC.
