The flood was voracious; it swallowed whole neighborhoods, ending hundreds of lives. But the battered levees have been repaired. They again stand between New Orleans and catastrophe, holding the Mississippi and Lake Pontchartrain in check. The antique drainage system, too, is back online. Any water that falls in the city, every drop of rain or tear shed, ultimately flows through canals until it's pumped over the levee into the lake. This is how New Orleans has been engineered: to control stray water, to clarify the border between the city and its surroundings.

It has been a losing battle. And yet, though it sounds particularly odd following Hurricane Katrina, the city's efforts have been spurred by the notion that nature favors it. From New Orleans' founding near the mouth of the Mississippi in 1718, the city has banked on geography to sweep it to greatness. Long before technologies circumvented the vagaries of geography, boosters claimed the city would reign over a commercial empire. But the local environs rarely cooperated with imperial visions. The lake and river loom above the city. Much of New Orleans lies below sea level, atop a high water table; there's no natural drainage. And pestilence thrives in the steamy delta. Scholars call this the disjuncture between"site"--the actual real estate a city occupies--and"situation"--an urban area's relative advantages as compared with other places. New Orleans, with access to the river and the gulf, enjoys a near-perfect situation. But it has an equally horrid site.

Geographer Peirce Lewis sums it up: New Orleans is"impossible" yet"inevitable." He means that if a city's situation is good enough, people will improve its site--no matter the costs. New Orleanians historically have done this by segregating spaces: at first not socioeconomically or racially but environmentally. In New Orleans there are spaces for nature: outside the levees or within the canals leading from the city. And there are spaces for human endeavors: within town. People here, nature there. The idea is simple, its execution impossible.

For now, water in the city seems under control again, back where people want it: in showers stripping away lingering grime, in strong coffee and confined behind the levees. Still, there's danger. Facing the challenge of rebuilding, New Orleans seems stuck in the mud--not just mired in the muck caking the city but also trapped by centuries of policy mistakes, especially the fantasy that it can be separated from its surroundings. This notion has been as destructive as the worst flood, and as difficult to avoid.

The people charged with rebuilding New Orleans seem enthralled by this mirage. They serve on committees--Mayor Ray Nagin's and Governor Kathleen Blanco's--with overlapping purviews and dubious authority. But despite their rivalries, the committees agree on at least one point: Levees must be top priority. Scott Cowen, Tulane University's president and part of Nagin's commission, suggests that without better levees other proposals--"world-class public education," improved housing, burnishing the city's" cultural ambience"--will be pointless. Andy Kopplin, executive director of the governor's panel, concurs:"We have to rebuild levees first, so people believe they're safe." To anyone familiar with the city's ecological history, this sounds like a recipe for more disasters.

From the first, New Orleanians augmented the levees. The project accelerated after an 1849 flood soaked the city for months. Federal authorities, alarmed by the inactivity of the nation's busiest port, sponsored two river studies. The first advocated multi-tiered flood control: levees, spillways and"reservoirs," swaths of wetlands acting like sponges. The second, penned by a future head of the Army Corps of Engineers, was more palatable at a time when wetlands were deemed wasteland. So began a policy known as"levees only." By 1900 New Orleans had levees taller than nearby houses. The river and lake had disappeared behind miniature mountains.

Just one problem: They didn't work. The river became more dangerous, and New Orleans less safe. With its water trapped behind levees, the Mississippi rose higher than ever. But you couldn't tell that to New Orleanians. Not even the huge 1927 flood fully changed their minds. That year the city dynamited a levee fifteen miles downstream, lowering the engorged river and destroying Plaquemines and St. Bernard parishes. The city had purchased its safety by sacrificing its poorer neighbors. (This event has fueled rumors in the Ninth Ward, where some residents and evacuees believe the levee fronting their district was destroyed after Katrina to protect wealthier, whiter areas.)

Still, the levees grew after 1927, despite federal inquiries in which conservationists testified that wetlands loss had exacerbated the disaster. The Army Corps of Engineers still refused to add wetlands to its arsenal. Instead, it built New Orleans a spillway that could shunt part of the river into Lake Pontchartrain--and, through the 1950s, continued to raise the levees.

Meanwhile, the city went on a building binge abetted by a drainage system constructed early in the twentieth century. For 200 years New Orleans had been trapped--a long, thin city on a narrow strip of relatively high ground shadowing the river. The Mississippi had flowed on one side, and a cypress wetland, the"backswamp," had stood on the other. After 1900, though, the city began reclaiming wetlands and expanding onto lower ground. By the 1960s the Lakefront neighborhood, the Lower Ninth Ward and other areas had replaced the backswamp. Ecological constraints had again yielded to ambition in a city captivated by its situation. With levees towering and wetlands gone, the segregation of landscapes seemed complete.

Sorting space had two other byproducts. First, more segregation: racial and socioeconomic this time. Before the 1950s New Orleans was a mixed city. Rich, poor, white, nonwhite--all were neighbors. This wasn't by choice but necessity; with development confined to high ground near the river, there wasn't room for people to move into socially segregated enclaves. But when developers started building tract housing on drained land in the city and nearby suburbs, New Orleanians became stratified, with poorer people of color often concentrated on low land and affluent whites typically occupying higher ground, if not the 'burbs.

The second consequence: Controlling nature became harder. Swamps disappeared, both because of urban reclamation and because levees diminished wetlands by keeping floodwaters from recharging the ecosystem. Oil exploration caused coastal erosion and swallowed thousands of acres of wetlands. For every foot the levees grew, it became that much harder to pump water out of the city. Finally, New Orleans began to sink as its watery foundation was replaced by spongy reclaimed land that compacted beneath the city's weight. Urban-environmental feedback loops caused the very problems New Orleanians had been trying to engineer out of their city's site for centuries.

In this setting Katrina made landfall. Its storm surge was too much for the levees. Water overtopped some; others collapsed. The pumps couldn't keep up, and New Orleans filled with water. Mostly the poor, people of color, the infirm and the elderly were left behind. Many died on low ground. The Brookings Institution reports that thirty-eight of greater New Orleans' forty-nine poorest districts flooded. In the city proper, 80 percent of the flooded neighborhoods were majority nonwhite. Segregation--environmental, socioeconomic and racial--resulted in segregated suffering.

The call now for improved levees is predictable. Joe Canizaro of the mayor's commission worries that nobody will return until they"feel safe." He's right. But what if people feel safe yet aren't? Before Katrina, disaster amnesia and denial allowed people to ignore the danger. Past disasters, says engineer Robert Bea of the University of California, Berkeley, were"alarm bells, but New Orleans kept hitting snooze." The city now has to rethink flood control.

Like most engineers, Bea is certain that levees can be constructed to withstand a Category 5 storm."It's just a matter of political will and funding," he says. But the funding isn't pocket change; the project requires billions. No one knows where that money will come from. While President Bush has promised the Feds will pay for levee repairs, he hasn't made the same promise about levee improvements. If the money is found, the political will must be sustained across fifteen years, the time needed to build levees to a Category 5 standard.

Even if those levees finally get built, they won't do the trick by themselves; engineers will have to learn to work with the city's peculiar ecology rather than trying to dominate it."Wetlands must be part of the solution," Bea says. If swamps aren't reintroduced, storm surges will overwhelm even the best levees. And if ocean levels keep rising and New Orleans keeps sinking, the city will drown again.

Craig Colten, a Louisiana State University geographer, agrees. He insists low-lying parts of the city shouldn't be rebuilt. His proposal is extremely controversial, with displaced residents understandably invoking their"right of return" and with most members of the reconstruction committees reluctant to reintegrate wetlands into the city after Mayor Nagin got burned for suggesting that the Ninth Ward might not be rebuilt. But Colten still believes that part of the backswamp should ooze into selected low-lying areas. An equitable method, he believes, would be to"take land from many neighborhoods--Lakefront, Ninth Ward, Gentilly--and relocate rich, poor, middle class to denser settlement on higher ground." Colten's"new New Orleans," then, would resemble the old New Orleans--from an era before wetlands vanished. It would also touch off battles over whose neighborhoods should be abandoned.

Danielle Taylor, dean of humanities at Dillard University, is certain that the outcome of such fights would favor the powerful. Returning urban districts to swampland, she contends, will shred the urban fabric, wrecking communities that made the city what it was. This echoes the views of Ninth Ward residents, who believe the city's elites saw the flood as the first in what will be waves of urban renewal. Absent affordable housing, redevelopment would leave no room for the poor and people of color, Taylor says. New Orleans would become a sterile--and white--preservation mall, with the French Quarter its anchor store. Colten sympathizes but says that allowing people to return to the lowest land would be"irresponsible."

What's certain is that segregating spaces hasn't worked. As Katrina demonstrated, it's impossible to separate social and environmental issues in this city. New Orleans isn't just a human artifact. Nor, of course, is it wholly natural. It's both: a network of human and nonhuman intermingled, straddling the nature/culture divide. The city must be rebuilt on a more solid foundation: the understanding that allowing no room for nature is as counterproductive as it is unlikely to succeed.

A fresh approach might yield sustainable urban spaces and environmental justice. But this would require hard choices unlikely to be made by committee. Sadly, New Orleans seems destined to find itself where it always has been: in harm's way.

Reprinted with permission from the Nation. For subscription information call 1-800-333-8536. Portions of each week's Nation magazine can be accessed at http://www.thenation.com.