National Geographic 10/2004: The Threat of a New Orleans Flood

Excerpt: The chances of such a storm hitting New Orleans in any given year are slight, but the danger is growing. Climatologists predict that powerful storms may occur more frequently this century, while rising sea level from global warming is putting low-lying coasts at greater risk. "It's not if it will happen," says University of New Orleans geologist Shea Penland. "It's when."
Yet just as the risks of a killer storm are rising, the city's natural defenses are quietly melting away. From the Mississippi border to the Texas state line, Louisiana is losing its protective fringe of marshes and barrier islands faster than any place in the U.S. Since the 1930s some 1,900 square miles (4,900 square kilometers) of coastal wetlands—a swath nearly the size of Delaware or almost twice that of Luxembourg—have vanished beneath the Gulf of Mexico. Despite nearly half a billion dollars spent over the past decade to stem the tide, the state continues to lose about 25 square miles (65 square kilometers) of land each year, roughly one acre every 33 minutes.