blufive

In October 2001, Scientific American ran an article on the hurricane threat to New Orleans:

If a big, slow-moving hurricane crossed the Gulf of Mexico on the right track, it would drive a sea surge that would drown New Orleans under 20 feet of water. [...]

New Orleans is a disaster waiting to happen. The city lies below sea level, in a bowl bordered by levees that fend off Lake Pontchartrain to the north and the Mississippi River to the south and west.

The gist, basically, was that a large storm surge, such as that created by a category 4 hurricane, would go over the top of the levees around the city, causing catastrophic flooding. A flood on that scale would probably flatten large parts of the city, and clearing the floodwater afterwards would require heroic levels of engineering.

The article goes on to outline potential methods to mitigate the situation, mostly revolving around long-term attempts to to rebuild the Mississipi delta flood plain south and west of the city. I doubt that much of that work has happened since the article was published.

A direct hit is inevitable. Large hurricanes come close every year. In 1965 Hurricane Betsy put parts of the city under eight feet of water. In 1992 monstrous Hurricane Andrew missed the city bu only 100 miles. In 1998 Hurricane Georges veered east at the last moment but still caused billions of dollars of damage.

Right now, there's a hurricane heading straight for New Orleans. Not just any old hurricane, either, but a full-on record-threateningbreaking Category 5 monster. The warnings currently being broadcast seem to be along the lines of "get as far the **** away from the coast as possible, yesterday if not sooner".

I just hope they can get everyone out in time, and/or Katrina decides to go somewhere less populous...

Much more over at Making Light (read the comments too, that's a blog with a seriously atypical comment-signal-to-noise ratio) and Stormtrack