The Best Defense Is a Good ... Marsh

Wayne Curtis is a freelance writer who's written for The New York Times, Atlantic Monthly, American Scholar, Preservation, and American Heritage, and is the author of And a Bottle of Rum: A History of the New World in Ten Cocktails. He recently traded Maine winters for New Orleans summers.

A couple of weeks ago, the Army Corps of Engineers made available a downloadable set of Google Earth overlays that depict post-2011 flooding forecasts for New Orleans. By then, the Corps will have improved the city's levees -- making them taller, better anchoring them to the ground, and partially armoring some against erosion with concrete. (Strategy for the next four years: Pray. Or cross your fingers if you're a Christopher Hitchens reader.)

Naturally, I downloaded the set, then occupied what could have been an otherwise productive afternoon by clicking the toggles and soaring like Superman across the city while watching the water rise and fall. It was more fun than anything by Nintendo.

Of course, this all seemed a little less fun when I zoomed in on my own block and found our house under six to eight feet of water. Yikes! After a few moments of harried mouse clicking, I realized I had forgotten to untoggle the pre-Katrina, one-in-500-year-storm forecast, the scenario in which basically the whole city gets the full Atlantis treatment.

So I clicked off the offending toggle, and discovered that not only was our neighborhood going to be high and dry through pretty much any future storm, but that the whole city looked pretty safe. Just a little puddle or two, really, would form here or there during a post-2011, once-a-century hurricane. (For the record, Katrina was a once-in-397-year storm. My advice: don't live here in 2402.)

This was all very heartening. But then it occurred to me: this compelling bit of computer wizardry was constructed by the same people who constructed the levees. The levees that, you may recall, overtopped, eroded, and breached during Katrina two years ago this week -- despite repeated assurances that they were safe.

Fortunately, the levees that surround the city are our second line of defense. Unfortunately, the first line of defense is the marshland that has historically served as a buffer between the city and the Gulf of Mexico. And the marshes are in even worse shape than the levees.

The Other Part of the Picture

Drive across one of the bridges over the Mississippi from the city center and, after some cursory cruising through suburbs, you'll find yourself in the marshes. To a newcomer like me, there's not much difference between one marsh and another, any more than there is between one Iowa cornfield and the next. The chief impression is that they're endless and flat.

Flat as they may seem, though, the marshes are, in effect, New Orleans' version of elevation. They protect this low-lying city from storm surges and hurricane winds by absorbing much of the energy of the wind and water. Having more marsh is like setting the city on a small hill. Having less marsh is functionally lowering it into the water.

Concern about the decline of Gulf of Mexico wetlands was a topic without much urgency around New Orleans prior to Katrina. After the storm, it attracted attention among a wider cadre. But it took a series on the coastal wetlands in the Times Picayune last March to really focus public attention. Suddenly, "marshes" was more commonly overheard in city coffee shops than "levees."

The three-part series contained a deluge of disheartening information about the pace of coastal erosion. Perhaps the one thing that cast it into sharpest relief was the large color photograph that led the series. It was an aerial shot looking south from just north of the central business district. It showed the instantly recognizable roof of the Superdome in the foreground, then the river, then a bit of marsh, and then the dappled Gulf of Mexico glistening in the spring sun.

To which everyone wondered: what the hell what was the gulf doing there?

New Orleanians have grown accustomed to telling people that the city lies about 60 miles from the sea. But here were those faraway waters, knocking at the back door.

Why the gulf has come visiting has little to do with global warming and rising seas -- at least not yet. It has everything to do with our efforts to control and exploit nature, and the blowback that's resulted.

Another aerial view puts in perspective not only the problem, but the cause. Each time I fly in or out of the city I peer out the jet window and see marshes extending to the encroaching gulf. But it's not an unmarred sea of grass. The marsh looks like a chessboard here, a gridiron there. Indeed, some 20,000 miles of canals have been sliced and diced to facilitate oil and gas vessels that cruise the marshes looking for deposits, and that want easier access to lay pipelines between the oil-rich gulf and fuel-processing facilities along the river.

This reckless network of canals, built over decades, caused a major breach in our defense, just as if someone had carved little ditches through the levees. The canals allowed salt water to invade freshwater marshes, killing the vegetation that had been keeping the alluvial silt in place. And the silt is the land here -- 10,000 years ago this was all sea; the soil-heavy Mississippi has been building up the delta ever since, and it's still pretty fragile. When the plants die, the mucky swamp soils rapidly erode into the gulf. Louisiana loses the equivalent of a football field about every 38 minutes. Between the hurricanes Katrina and Rita -- the disagreeable sisters of 2005 -- some 200 square miles of marsh washed away.

Silt Crazy After All These Years

Gulf hurricanes are nothing new, of course. They have washed away marshes for centuries. But historically, the marshes would have replenished with silt carried by the Mississippi when it overflowed its banks. Today, the river sits straitjacketed by the levees that encase it for much of its length. Instead of spreading out across the wetlands during flood times, the Mississippi River dumps its great load of silt off the continental shelf and into the depths of the Gulf of Mexico, benefiting no one.

The map of Louisiana in that atlas on your shelf? It's likely drawn from data compiled more than a half century ago. Much of that marshland depicted on maps at the mouth of the Mississippi -- it's poetically called the birdfoot delta -- is gone. Your atlas is like an old family album showing ghosts of the past.

Among the more stunning points in the newspaper series was this: scientists say we've got just one decade -- a scant 10 years -- to reverse coastal erosion or it will be too late. Too late meaning that the ocean will be flowing into the backyards of New Orleans suburbs, and levees designed to keep out the infrequent flood will be employed full-time to keep out a permanent gulf intrusion.

It's not that the fix couldn't be achieved more than a decade from now. But the erosion would be so advanced that the cost of rebuilding the coastal wetlands would be prohibitive by almost any measure. As it stands, it's uncertain how much tolerance taxpayers have to fund the many billions already needed to undertake the massive diversion projects that would get the alluvial silt where it needs to be.

The city can't do this alone, and the state can't do it alone. It will require a major effort on the part of the federal government to fix what the oil and gas companies and eager-beaver levee builders have wrought.

There is some good news. Success has been marked in the Atchafalaya Basin to the west of New Orleans, where about one-third of the Mississippi River flows into the gulf. In the past 20 years, thanks to river diversion projects that allow the outflow of the Mississippi to rebuild eroding wetlands, the landmass is growing, and the landscape is healing. It can be done.

As I wrote in the first dispatch, to move to New Orleans post-Katrina is to show your faith in technology. Actually, that's not wholly correct. The technology is there, and it's looking pretty good. It's the political will that's more of concern. Getting the ideas from the drafting table to the bulldozers takes cash and political influence -- things our city doesn't have in much surplus these days.

The second anniversary of Katrina is being marked this week with a great flurry of stories in newspapers, magazines, and television about the recovery, both good and bad -- and there's plenty each to report. Next week, the hordes will leave and a late summer silence will fall upon the city as the media chases the next story. (What has Lindsay Lohan been up to the last month, anyway?)

But the slow process of healing and protecting this extraordinary city will push on, one day at a time. The ultimate destination? Unknown.