Watermark: can southern Louisiana be saved

New Orleans Flooded after KatrinaElizabeth Kolbert, a writer for the New Yorker, who also wrote a series of articles – Climate of Man – about climate change. Wrote a fairly grim article Watermark: can southern Louisiana be saved, in the Feb 27, 2006 New Yorker. She writes about geology, wetland loss, climate change, and people of New Orleans.

Five thousand years ago, much of southern Louisiana did not exist. A hundred years from now, it is unclear how much of it will remain. The region, it is often observed, is losing land at the rate of a football field every thirty-eight minutes. Alternatively, it is said, the area is shrinking by a large desktop’s worth of ground every second, or a tennis court’s worth every thirteen seconds, or twenty-five square miles a year. Between 1930 and 2000, some 1.2 million acres, an area roughly the size of Delaware, disappeared. Hurricanes Katrina and Rita stripped away an estimated seventy-five thousand acres—a loss as big as Manhattan and Brooklyn combined. The U.S. Geological Survey has published a map illustrating the process. Areas that have already vanished appear in red, and areas that are expected to vanish by 2050 in yellow. On the map, the southern coast looks as if it were on fire. According to the U.S. Army Corps of Engineers, “The rate at which Louisiana’s land is converting to water is probably the fastest in the world. [here is an animated map]

Dokka’s study, which he published in July, 2004, under the title “Rates of Vertical Displacement at Benchmarks in the Lower Mississippi Valley and the Northern Gulf Coast,” showed that for decades elevations in coastal Louisiana had been systematically overstated. Heights had been calculated on the basis of “benchmarks” that were supposedly stable but which, it turned out, were themselves subsiding. Dokka’s calculations showed that the fastest-sinking areas, among them the southern part of Plaquemines Parish, were losing elevation at the rate of more than an inch a year. In his study, he labelled this phenomenon an “inexorable slow disaster” whose economic effects would eventually “be felt by the entire country.”

The Mississippi swung into its present course—and began to lay down Plaquemines Parish and the Birdfoot—approximately a thousand years ago. At this point, it is ready to switch direction yet again. For several decades, the river has been trying to jump its banks to follow a steeper gradient that leads to the Gulf of Mexico through the Atchafalaya River Basin, between Baton Rouge and Lafayette. The Old River Control Structure, which is twelve hundred feet long and consists of an elaborate series of dams, locks, and sluices, has prevented this from happening. But while the control structure has preserved New Orleans’s viability as a port—were the river to change course, the city would face out onto slack water of the sort found in Bayou Lafourche—it has done nothing to solve the problem of land loss. Indeed, just the reverse. Instead of going into delta-building, most of the Mississippi’s sediment today gets dumped beyond the Birdfoot and off the continental shelf….

The fundamental problem of southern Louisiana—the fact that making the area suitable for permanent settlement also tends to make it that much more impermanent—has been understood for many decades. In the nineteen-twenties, Percy Viosca, a Louisiana naturalist, warned that flood-control and land-reclamation efforts were “killing the goose that laid the golden egg”; he advocated that the state adopt policies to reëstablish the “natural conditions” conducive to healthy marshes. Instead, though, virtually all the practices that exacerbate land loss were allowed to continue and, in some cases, even encouraged. Swamps were drained to create agricultural fields and housing developments; this caused the peaty marsh soils to oxidize and shrink, like a drying sponge, resulting, in many instances, in new expanses of open water. Navigational channels like the Mississippi River-Gulf Outlet were dug; these carried salt water into what had been freshwater marshes, killing trees and grasses and inviting erosion. Thousands of miles of canals were cut into the wetlands to facilitate oil and naturalgas exploration; much like the navigation channels, these canals wreaked havoc on the local hydrology. Where oil was found, the process of extraction caused some areas to slump—Louisiana “floats on oil like a drunkard’s teeth on whiskey,” A. J. Liebling once wrote—further contributing to subsidence.

Although almost no one in or outside New Orleans seemed prepared for it, Katrina was probably the most comprehensively predicted catastrophe in American history. In the past few decades, storm-surge models have become increasingly sophisticated and the computers they run on increasingly powerful. When researchers began to adapt the models to New Orleans, they became convinced, as one of them put it to me, that “we had this train wreck imminent.” The city’s levees had been designed to protect it from what the Army Corps of Engineers calls a “standard project hurricane”—roughly, a fast-moving Category 3 storm. (Since fast-moving storms have less time to pile up water, they’re generally less dangerous than slow-moving ones.) But not all of the levees met this objective, even on paper. A project to upgrade them, begun in the aftermath of Hurricane Betsy, in 1965, was repeatedly delayed by funding cuts; by 1995, it was still twenty years from completion. Meanwhile, as the levees were slowly being raised, the land underneath them continued to subside. The models showed that, even if New Orleans’s defenses held up, many possible hurricanes could overwhelm them, and that in the fastest-subsiding coastal parishes a relatively minor storm could prove devastating.

[Judith] Curry pointed out that, thanks to global warming, not only were hurricanes becoming more intense but sea levels were rising, making storm surges that much more dangerous. “What used to be the once-in-a-lifetime flood, you could see every season,” she observed. In terms of rebuilding New Orleans, Curry said, “It’s a complex issue. But, speaking from the climate and the environmental-science perspective, a hundred years from now there’s just no way there’s going to be a city there. You just know that isn’t going to happen. We can fight it. We can rebuild it and wait until it gets wiped out again. If you look at the geological record, these coastal areas come and go. Sometimes they’re under water and sometimes they’re not. Maybe a colossal engineering effort can do something, but at some point that is going to fail. This is just the way geology and climate work. You can’t fight it forever.”

Percy and Solomon, Jr., had both grown up in the Lower Ninth, and in 1965 they had ridden out Hurricane Betsy in a two-story house a few blocks away. “Listening to the Mayor saying, ‘Come back,’ once you come back and see this city, you see he’s just saying that stuff,” Percy observed. “It’s hard to fathom.” He gestured toward his father’s house and the house next to it, which had also been swept off its foundation, and a third house, which was listing crazily. “Would you want to rebuild this? I mean, really? What happens next September? Every year, it’s going to be the same thing.”
Percy turned to his father and asked him if he thought he would return. The old man shook his head.
“No,” Percy said. “Let it go.”

The New Yorker has an online archive of all its articles on Katrina.

2 thoughts on “Watermark: can southern Louisiana be saved”

  1. Perhaps the wise thing to do would be for the State of Louisianna and the City of New Orleans to acquire the land above the Old River Control structure and between the Red and Mississippi rivers for the purposes of laying out a new city site. It’s a nice high groud site, that is probably as close to the gulf as one can locate a large city near the delta and have a reasonable chance of it survining for the long term. In effect, start a 50-100 year process of pulling back from the lower delta with a hard target for letting the rivers return to their natural cycle of periodic channel switching. The city would then be in a pretty good position assuming that sea level rise from global warming is less than something around 75 feet. The actual sea level rise we are going to experience is not yet clear. Estimates on the low side are around 15 feet, and on the high side are 250 feet (that assumes that all of Greenland and Antartica melt). While the 250 foot figure is currently considered “inconceivable,” population growth and development projections which drive CO2 release into the atmosphere, are currently on track to force a complete melt, unless something changes sooner. Right now, development in China is accelerating, not slowing. We may be any where from three to fifteen feet deeper by 2050, but where we are in 2150 is ugly. My suggestion for gradually moving New Olreans assumes that the mouth of the river stays in Louisianna. The melt is non-linear and when exactly the large Greenland and Antartic ice sheets that are holding back the land based glaciers are going to melt is not clear. But when it happens, the rise will start accelerating very quickly, and it will be way too late to implement a carefully thought out and well executed plan for saving places like New Orleans by relocating them to better sites. New Orleans is a great city. It would be a shame to lose it permanently simply because we could not bring ourselves to do what has to be done while there is still time to do it. Again, even this plan has an element of risk in that it assumes that global warming will be no worse than anything that has happened in the past 100 million years or so. It could be worse, but I would think we should at least gamble that it won’t be. In any event, such a bet would make a heck of a lot more sense than ignoring the bigger picture and trying to keep the city where it is. That strategy is guaranteed to fail, and probably within the next 50 years, even if it doesn’t get slammed by another category 3 or bigger hurricane. Maybe it would be a blessing to have the city get hit again this year, so people start getting realistic about what the options are, and stop wasting so much time and precious capital on a lost cause.

  2. My grandfather was the cited Percy Viosca, Jr., biologist who for many years warned of preserving the wetlands. Although he died in 1961, he is still often cited. My Mom (his daughter) and I would often see these cites. Good luck. (Mom has just died at age 84 but was well aware of her Dad’s works.) Supposedly, Louisiana has a research vessel named after Percy Viosca, Jr. Many of the Viosca relatives were discussing these events at Mom’s funeral this week. ‘Paul M

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