Reply #14: We Got Lucky With Katrina And Rita

[Strelnikov_]

If Katrina had tracked 40 mi. further west, and maintained strength to landfall, we probably would not be talking about rebuilding New Orleans, in addition to losing critical petroleum and natural gas staging and offloading facilities.

If Rita had tracked 50 mi. further south, the Houston petrochemical industry, which includes 15% of the nations refining capacity, would have been taken out.

Combine the above two, and we could have the beginning of Petrocollapse.

So, considering the upcoming season, you've got to ask yourself a question: Do I feel lucky?

Most of New Orleans flooding was due to discrete levee failures, somewhat limiting the rate of rise. Under the following hurricane scenarios, the entire City is swamped under storm surge, overtopping the levees simultaneously. Katrina was not the big one. Not even close.

In the 1990s, Suhayda began modeling category 4 and 5 storms hitting New Orleans from a variety of directions. His results were frightening enough that he shared them with emergency preparedness officials throughout Louisiana. If such a severe storm were to hit the city from the southwest, for instance, Suhayda’s data indicate that the water level of Lake Pontchartrain would rise by as much as 12 ft (3.7 m). As the storm’s counterclockwise winds battered the levees on the northern shore of the city, the water would easily top the embankments and fill the streets to a depth of 25 ft (7.6 m) or more.

Suhayda’s model is not the only one that describes such a catastrophe. A model called SLOSH (Sea, Lake, and Overland Surges from Hurricanes), which is used by the National Weather Service and local agencies concerned with emergency preparedness, portrays an equally grim outcome should a storm of category 5 hit New Orleans. The SLOSH model does not contain nearly as many computational nodes as does AdCirc, it does not use a finite-element grid to increase the resolution of the nodes on shore, and its boundary is much smaller. Even so, its results are disheartening.

“Suppose it’s wrong,” says Combe, the Corps modeler. “Suppose twenty-five feet is only fifteen feet. Fifteen feet still floods the whole city up to the height of the levees.”

Experts say a flood of this magnitude would probably shut down the city’s power plants and water and sewage treatment plants and might even take out its drainage system. The workhorse pumps would be clogged with debris, and the levees would suddenly be working to keep water in the city. Survivors of the storm—humans and animals alike—would be sharing space on the crests of levees until the Corps could dynamite holes in the structures to drain the area. In such a scenario, the American Red Cross estimates that between 25,000 and 100,000 people would die.

- Civil Engineering Magazine, June 2003