New Orleans: A Perilous Future

Hurricane Katrina, the costliest natural disaster in United States history, was also a warning shot. Right after the tragedy, many people expressed a defiant resolve to rebuild the city. But among engineers and experts, that resolve is giving way to a growing awareness that another such disaster is inevitable, and nothing short of a massive and endless national commitment can prevent it.

Located in one of the lowest spots in the United States, the Big Easy is already as much as 17 feet (five meters) below sea level in places, and it continues to sink, by up to an inch (2.5 centimeters) a year. Upstream dams and levees built to tame Mississippi River floods and ease shipping have starved the delta downstream of sediments and nutrients, causing wetlands that once buffered the city against storm-driven seas to sink beneath the waves. Louisiana has lost 1,900 square miles (4,900 square kilometers) of coastal lands since the 1930s; Katrina and Hurricane Rita together took out 217 square miles (562 square kilometers), putting the city that much closer to the open Gulf. Most ominous of all, global warming is raising the Gulf faster than at any time since the last ice age thawed. Sea level could rise several feet over the next century. Even before then, hurricanes may draw ever more energy from warming seas and grow stronger and more frequent.

And the city's defenses are down. Despite having spent a billion dollars already, the U.S. Army Corps of Engineers now estimates it will take until after 2010 to strengthen the levee system enough to withstand a 1-in-100-year storm, roughly the size of Category 3 Katrina. It would take decades more to protect the Big Easy from the truly Big One, a Category 4 or 5—if engineers can agree on how to do that and if Congress agrees to foot the almost unimaginable bill. For now, even a modest, Category 2 storm could reflood the city.

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