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Politicians can’t ask, but the question is reasonable: Why rebuild?

As Gustav churned through Louisiana and more hurricanes poise to pound the Gulf and East Coasts, those whose homes and towns are mangled instinctively organize a recovery and begin yet another rebuilding.

As Gustav churned through Louisiana and more hurricanes poise to pound the Gulf and East Coasts, those whose homes and towns are mangled instinctively organize a recovery and begin yet another rebuilding. It’s the human spirit to fight back, after all; we oblige by wishing them well, and sometimes interrupt a party to raise money to help out. 
But it’s reasonable to ask whether it makes sense in every case to set things back up when it’s a dead certainty that another hurricane will be back. It’s a matter of time, something that’s decidedly on nature’s side.
Now, if you’re a politician seeking to stay in office or get there, it’s risky to talk about these things. Ask Dennis Hastert, the Illinois Republican and speaker of the House, who three years ago — after Katrina left 1,400 dead and entire neighborhoods of New Orleans flooded in one of the nation’s worst disasters — simply asked whether the city should be rebuilt. He had to retract the remark, and shut up evermore. Still, it’s a question that deserves a reasonable discussion.

New Orleans is in attention’s eye, due to the freshness of Katrina’s devastation and the sloppy government response to it and, now, Gustav’s untimely appearance as the Republican National Convention in St. Paul began. 
New Orleans has a charming history that beckons America’s heart, especially if you’re fond of jazz and Mardi Gras and Creole food and Cajun culture and an all-around good time. Who isn’t?

Unyielding river geology
But New Orleans is perhaps the very worst place for a city to be located, and given some unyielding river geology and the inevitabilities of climate change, the choices come down to:  giving up on the city for the most part, or continuing to pour billions and billions of dollars into maintaining a city where nature says it shouldn’t be. 
As you think about that, remember that nature never loses — no matter what the U.S. Army Corps of Engineers and New Orleans’ boosters may pretend to believe. Sooner or later, levees give way.    
Old New Orleans made sense. It was a garrison at the mouth of the mighty Mississippi and gateway to a new nation’s western frontier, built on the only mound of high ground that was surrounded by a large, half-moon bend of the river (hence the name, “Crescent City”). The French Quarter wasn’t flooded by Katrina, and before that Betsy (1965), because it was the original bump of earth above sea level that, in time, saw a metropolis push into the Lake Ponchartrain swamp with levees and pumps — making habitation possible on land as much as 10 feet below sea level. 
Problem is, the land continues to sink — and the ocean continues to rise. 
Massive loads of sandy silt
New Orleans is in the “delta” portion of the Mississippi, where the slowing river current deposits massive loads of sandy silt that, over time, cause the river channel to move back and forth as it seeks to escape its own silt buildup and find the easiest path to the ocean. 
Wet silt builds up, but levees have dried out the delta that is much of New Orleans. Dry silt compresses and organics evaporate in a process called “subsidence.” That’s why homes built on dry land behind the levees are slowly falling deeper and deeper relative to the ocean that, it turns out, is rising and rising.   
Climate change is causing oceans to rise, explaining why the Dutch are deep into planning on ways to top the mighty dykes that keep much of Holland dry against the ever-rising North Sea. Rising oceans are affecting coastal areas throughout the world, but the effects are most sharply felt where land next to them is actually below sea level, as it is in much New Orleans and The Netherlands.   
Which means that the hundreds of miles of levees must constantly be maintained to keep the ocean out. The lattice-work of levees from New Orleans to the sea leaves the city on life-support and protect agricultural fields from salt-water intrusions that, if allowed in, would turn productive lands to a shallow, briny swamp teeming with shrimp and fish and wildlife.     
Levees keep river from meandering
The levees also keep the Mississippi River from meandering through swamps and wetlands built by the river’s own fanning action. As in Amsterdam, there are places in New Orleans where you look UP at sea-going ships. And over time you will have to look higher and higher as subsidence lowers land and the sea keeps rising. 
The heating ocean caused by climate change does something else: it intensifies hurricanes that are fueled by warm water, some of which in the Gulf cooks to nearly 90 degrees. If, as Katrina did, a hurricane stalls over warm water, it can push to a Category 5 blockbuster whose deadly spin and blankets of rain can cause bring destruction far inland. 
But by channelizing the Mississippi and preventing the build-up of silty shores, something else occurs: destruction of wetlands to allow boat access to offshore derricks that pump up oil and natural gas. Rising oceans and wetland destruction gave Katrina and Gustav, along with those that follow, an easy path to the built-up city, thus increasing the potential for damage. 
But as well, the Mississippi River doesn’t even want to go through New Orleans. Had the Corps of Engineers and State of Louisiana not intervened in the 1950s, it’s very likely that the river wouldn’t flow past the city at all. 
On your map, follow the Mississippi from New Orleans upstream until it intersects with the south-flowing Atchafalaya River.  It’s a basin that would allow the Mississippi easier access to the ocean and it’s the route the Mighty Miss naturally would follow. 
The official policy of the state and federal government is to allow only 30 percent of the Mississippi’s water to flow into the Atchafalaya, and massive dikes help ensure that enough water remains in the main channel — now called the “Old River” — to protect sea-going commerce in New Orleans.

During flood, huge gates open
In the event of a flood, huge gates on Atchafalaya’s dikes are opened to allow torrents of water to pass into the “new” channel and keep the water from spreading around and undercutting the structures and destroying them. 
But, engineers agree, it’s only a matter of time before a massive flood overwhelms the structures and the entire Mississippi flow goes where nature intended, and down the Atchafalaya. That would mean New Orleans would cease as a shipping port and its primary reason to exist would be gone. 
It’s all just a matter of time. 
Meanwhile, the easy political choice is to join emotional pleas to rebuild the city and reinforce levees just enough to give some semblance of comfort to those who remain.  But the truth is, it would be far less costly to the American taxpayer to relocate the entire city — including building new homes for its transferred residents — than to continue to rebuild and maintain a levee and dike system that is destined to fail.