From an article published six weeks ago:
The chief danger to New Orleans is a storm surge. Wetlands attenuate the height of a surge, at a rate of about one foot for three miles. But in the Barataria Basin south of the city, 15 miles of marsh have deteriorated, according to the United States Geological Service. A slow-moving Category 5 hurricane could produce a 19- to 21-foot storm surge in Lake Pontchartrain, higher than the levees that protect the city. New Orleans could find itself under 20-25 feet of water.Fascinating reading. As one of my email list buddies says, "CNN could be reading directly from this article".