The Big Easy On the Brink

By ADAM COHEN

If a flood of Biblical proportions were to lay waste to New Orleans, Joe Suhayda has a good idea how it would happen. A Category 5 hurricane would come barreling out of the Gulf of Mexico. It would cause Lake Pontchartrain, north of New Orleans, to overflow, pouring down millions of gallons of water on the city. Then things would really get ugly. Evacuation routes would be blocked. Buildings would collapse. Chemicals and hazardous waste would dissolve, turning the floodwaters into a lethal soup. In the end, what was left of the city might not be worth saving. "There's concern it would essentially destroy New Orleans," says Suhayda.

Suhayda, a water-resources expert at Louisiana State University, is the kind of guy who could have given Noah a computer model of all 40 days and 40 nights of rain, including the Ark's soft landing on Mount Ararat. So it is real cause for concern that he has joined the chorus of scientists and environmentalists who are saying that the watery threat to New Orleans is extreme--that in the worst-case scenario, in fact, there might not be a city of New Orleans left standing by the end of the century.

New Orleans has always had a complicated relationship with the water surrounding it. Everyone told the first settlers this was the wrong place to build a city. It is wedged precariously between the mighty Mississippi and Lake Pontchartrain, and most of it was once swampland. Aggravating the problem is the fact that much of New Orleans is below sea level, so that after a good rain, the water just settles in. There is now a decent pumping system, which helps. Old-timers, however, still talk of the days when, after a bad storm, bodies washed out of the cemeteries.

What is threatening New Orleans is a combination of two man-made problems: more levees and fewer wetlands. The levees installed along the Mississippi to protect the city from water surges have had a perverse effect: they have actually made it more vulnerable to flooding. That's because New Orleans has been kept in place by the precarious balance of two opposing forces. Because the city is constructed on 100 feet of soft silt, sand and clay, it naturally "subsides," or sinks, several feet a century. Historically, that subsidence has been counteracted by sedimentation: new silt, sand and clay that are deposited when the river floods. But since the levees went up--mostly after the great flood of 1927--the river has not been flooding, and sedimentation has stopped.

The upshot is that New Orleans has been sinking as much as 3 ft. a century. That's bad news for a city that is already an average of 8 ft. below sea level. Making things worse: sea levels worldwide are rising as much as 3 ft. a century on account of global warming. The lower New Orleans plunges, the worse it will be when the big one hits.

New Orleans' other major man-made problem is that its wetlands and its low-lying barrier islands are disappearing. The Louisiana coast is losing 16,000 acres of wetland each year, mostly as a result of population expansion into once pristine areas, destructive oil and gas drilling, pollution and land loss through lack of sedimentation. As it turns out, wetlands and barrier islands aren't just nice to look at; they are also a key natural barrier to hurricanes. (Every 2.7 miles of wetland absorbs a foot of storm surge.) As the wetlands go, the chance of a hurricane blowing the city away grows.

So environmentalists and engineers are frantically coming up with plans to save New Orleans. One idea is to raise levee walls to increase their effectiveness against storm surges. Another is to create large-scale diversions that would allow the Mississippi to flood in a controlled manner--and through sedimentation add thousands of acres a year of new land. Yet another would be to take immediate steps to reverse the loss of sensitive wetlands. Adding land through sedimentation is one of the best ways of restoring wetlands. Among other possible schemes: cutting back on shipping routes that harm marshes, installing wave absorbers to reduce wetland erosion and rebuilding damaged barrier islands.

The big sticking point, not surprisingly, is money. The price tag for a complete solution could be as much as $14 billion in federal and state money--which may be more than Washington wants to spend, and more than Baton Rouge can. But experts are also working on scaled-down remedies, including construction of a "curtain wall" that would bisect the city, creating a safe haven to which residents could evacuate.

So far, little has been done. Part of the problem, of course, is that excessive worrying and planning are radically at odds with the spirit of the Big Easy. Despite the damage inflicted by Hurricane Betsy in 1965 and the near miss of Andrew in 1992, New Orleans is still a place where the primary meaning of hurricane is a fruity rum drink the law lets you carry openly as you carouse in the French Quarter. While the grimmest of the doomsayers warn that New Orleans could be the next Atlantis, some laid-back residents are saying that it could just as easily become the next Venice and that after the deluge, the good times won't roll--they'll float.