In the event of a slow-moving Category 4 or Category 5 hurricane (with winds up to or exceeding 155 miles per hour), it's possible that only those crow's nests would remain above the water level. Such a storm, plowing over the lake, could generate a 20-foot surge that would easily overwhelm the levees of New Orleans, which only protect against a hybrid Category 2 or Category 3 storm (with winds up to about 110 miles per hour and a storm surge up to 12 feet). Soon the geographical "bowl" of the Crescent City would fill up with the waters of the lake, leaving those unable to evacuate with little option but to cluster on rooftops -- terrain they would have to share with hungry rats, fire ants, nutria, snakes, and perhaps alligators. The water itself would become a festering stew of sewage, gasoline, refinery chemicals, and debris.
I thought of the city’s vulnerability recently, when the latest news came out from the National Oceanic and Atmospheric Administration: We can expect another very active Atlantic hurricane season this year, beginning on June 1 and stretching to the end of November. Last year, four hurricanes devastated swaths of Florida. One of the biggest ones, Ivan (a Category 4 storm) seemed to have New Orleans in its sights for a while. Ivan triggered a mass evacuation -- members of my family scrambled to Shreveport, Baton Rouge, and Houston -- but ultimately missed the city. Now, however, New Orleanians are in for another nail-biting fall and once again must contemplate the possibility of the dreaded "Atlantis scenario" becoming reality.
A direct hit from a powerful hurricane on New Orleans could furnish perhaps the largest natural catastrophe ever experienced on U.S. soil. Some estimates suggest that well over 25,000 non-evacuees could die. Many more would be stranded, and successful evacuees would have nowhere to return to. Damages could run as high as $100 billion. In the wake of such a tragedy, some may even question the wisdom of trying to rebuild the city at all. And to hear hurricane experts like Louisiana State University's Ivor van Heerden tell it, it's only a matter of time before the "big one" hits.
Currently, pretty much every long-term trend cuts against the safety of New Orleans. Levees are subsiding; coastal wetlands (which can slow storm surges) are continually disappearing; and sea levels are rising. And then there's global warming -- a warmer world with warmer ocean temperatures should theoretically experience worse hurricanes. Most importantly, the Atlantic Ocean appears to have entered an active hurricane cycle, with the potential to fling storms at the Gulf Coast for years to come. This puts New Orleans on the vanguard among U.S. coastal cities (including New York) that will have to think hard about their growing vulnerabilities in the coming years. The process of deciding how to save an entire coastal metropolis has begun, but the discussion has largely been confined to experts, and not nearly broad or ambitious enough yet.
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