Before Katrina, Hurricane Camille was thought of as this nation's worst hurricane. In 1969, Camille made landfall 20 miles east of where Katrina did with winds almost 50 mph stronger than Katrina's. Camille caused 256 deaths, most from wind damage and storm surge along the Mississippi coast. Photos of Camille's damage are eerily similar to images of Katrina: trees stripped of leaves, homes leveled. Camille and Katrina had similar effects along the Mississippi and Alabama coastlines.
That stretch is much more developed and populated now than it was 36 years ago, so the damage from Katrina far exceeds that of Camille.
Storm surge is the wall of water that accompanies a hurricane. It is not one massive wave, like a tsunami. Instead water slowly piles up because of hurricane winds pushing across the ocean's surface for a long period of time. As the storm surge becomes greater the stronger the winds are, the longer they move over the same ocean waters, and the larger an area is affected.
Katrina's surge was as high as 30 feet partially because the combination of those three factors was as great as with any land-falling U.S. hurricane. That surge exceeded the 24-foot storm surge associated with Camille (at the time the record for a hurricane hitting the United States.)
Katrina's size and closer path, compared with Camille, made the difference in New Orleans. Hurricane-force winds extended more than a hundred miles from Katrina's center. That created a storm surge that was high and expansive. Its path, passing just east of New Orleans, was a worst-case scenario, too.
The wind first funneled water into Lake Pontchartrain as easterly winds prevailed on the north side of the storm. Then, as the storm moved north, winds on the west side of the storm were from the north, so that excess water in the lake was pushed toward downtown New Orleans.
The levees were built to contain about an 18-foot storm surge. They would have fared fairly well, except that the water sloshing in the lake eroded the levees from underneath. New Orleans is equipped to pump water out of the city, but the pumps deposit the water back into Lake Pontchartrain, the source of the floodwaters.
However, the eye of the storm could have been closer to New Orleans. The winds could have been stronger. Either would have caused an even higher storm surge and more damage, though that is difficult to imagine.