Tuesday, August 30, 2005

Katrina/New Orleans Update: Bad News

It appears that my previous post on the effects of Hurricane Katrina, while horrific, was too optimistic.

Late reports indicate that there has occurred at least one major levee break in the line of defense between the city of New Orleans and adjacent Lake Pontchartrain. The Army Corps of Engineers along with state and local officials is desparately trying to fill the breach to prevent the below-sea-level city from turning into a giant lake.

As the following reports recently posted by Brendan Loy at Irish Trojan's Blog indicate, it is no exaggeration to describe today's desparate struggle as the second "Battle of New Orleans." Unlike the first one, however, this is a fight for the life and death of the city itself.

The view from St. Amant
8/30/2005 01:05:00 PM EST
Posted by Brendan

Bill Crews reports in from St. Amant, southeast of Baton Rouge:

Still w/o power here in St. Amant. I've been tuned into WWL 870 AM. They are transmitting w/an approximate 28 day supply of propane to generate their transmitter. Still operating out of the Omni (?) Building, located next to the 'S-dome. That's one of the buildings w/all the glass & doors blown out of it. Here are some comments I've heard in the last few hours: "City still continues to flood due to levee breach...""Lower half of Plaquemines Parish has been reclaimed by Gulf of Mexico and Miss. River...""North shore of Lake Ponchartrain now extends (N) to Old Spanish Trail Rd...""The Ponchartrain Causeway was completely submerged except for the 'hump' in the middle...""Martial law has been declared...""The Miss. River levee was beached from Belle Chase, southward...""Search and rescue efforts still continue..." BTW, officials are now asking all refugees to go to the Lamar Dixon Expo Center, near my home, in Gonzales, LA. We may go volunteer later; they are expecting thousands.

Officials to attempt sandbag airlift
8/30/2005 11:30:00 AM EST
Posted by Brendan

WWL-TV: "Break in 17th Street Canal Levee is now 200 feet wide and slowly flooding the City of New Orleans. Huge sand bags are being airlifted to try to stem the rush of water in that area. The expectations are that the water will not stop until it reaches lake level." In other words, we are talking about something that very closely resembles the worst-case scenario -- flood waters completely filling the bowl, turning Lake Pontchartrain and New Orleans into one big toxic lake. This will will happen, unless the airlift works or officials can find some other way to stem the flood.Anthony sums up the situation succinctly:

"assuming no additional storm surge, or Mississippi floodwaters, the water level in the 'bowl' will end up being effectively equal to the level in Lake Ponchatrain."

Cliff, a hydrologist, gives an excellent, more detailed explanation of why that's true.Does anyone know what the typical water level in Lake Pontchartrain is, in comparison to the various regions of the city? How many feet above the French Quarter? How many feet above Tulane University? etc.Regarding whether the sandbagging plan will work, Cliff writes:

It's difficult to say without knowing exactly how deep the breach actually is. The fact of the matter is, even if they can reduce the width of the breach from 200ft down to 100ft or 50ft, then they will potentially slow down the amount of water coming into the city. The depth of the breach also determines how fast the water is moving across it, and if the velocity is high enough, it's possible that the sandbags won't hold. Blocking the actual canal with sandbags/barges is a good alternative I think, but it obviously requires a lot more volume of stuff to block it with. From the one photo I've seen, if the breach is actually 200ft wide, by scale, the canal looks to be at least 3x as wide as the breach, and if it's 10ft deep, that's a lot of volume to try & block. Like I said, it's difficult to make an estimate not knowing all the information. But if they only need to block a couple of feet in the breach, then that would require far less material than blocking the canal.

On a more hopeful note, "The LSU researchers [speaking on WWL-TV] indicated that they thought the breech could be sealed," according to another commenter.