Wednesday, September 21, 2005
Seawalls not overtopped in New Orleans according to researchers
I hate that everybody refers to these as levees and not seawalls, but what are you gonna do. Anyhow, this is quite the thought-provoking piece, I highly recommend it.
"...the researchers have strong evidence that Katrina's subsequent surge from the north was several feet shy of the height that would have been necessary to overtop the 17th Street and London Avenue floodwalls. It was the failures of those floodwalls that emptied the lake into the rest of the city, filling most of New Orleans like a soup bowl.
On a tour Tuesday, researchers showed numerous indications that Katrina's surge was not as tall as the lakefront's protections. They showed a "debris line" that indicates the top height of Katrina's waves was at least four feet below the crest of Lake Pontchartrain's levees. They also pointed out how the breached floodwalls near the lake showed no signs of overtopping — no splattering of mud, no drip lines and no erosion at their bases. They contended that the pattern of destruction behind the breaches was consistent with a localized "pressure burst," rather than widespread overtopping.
The center has also completed a computerized "hindcast" of Katrina, which has confirmed the evidence before their eyes. Their model indicates that most of the surge around the lake and its nearby canals was less than 11 feet above sea level, and that none of it should have been greater than 13 feet. The Army Corps' flood-protection system for New Orleans was designed to handle surges of more than 14 feet above sea level.
"This should not have been a big deal for these floodwalls," said oceanographer G. Paul Kemp, a hurricane expert who runs LSU's Natural Systems Modeling Laboratory. "It should have been a modest challenge. There's no way this should have exceeded the capacity."
Full story here