E-mail from someone following this closely:

–Subject: Emerging consensus from my sources at Corps offices in New Orleans
Rich, the article from this morning’s New Orleans Times-Picayune is what I have been hearing since this weekend. Namely, the amount of funding for the flood control efforts (high or low) is not the issue here, but that newer structures built since 1995 were flawed. The 17th Street Canal sections were completed only within the last 18 months. The main breaches appear to all be from SELA [Southeastern Louisiana Flood Control Project] or post 1995 construction efforts that are concrete rather than earthen — like the Mississippi River levees…
Mystery surrounds floodwall breaches Could a structural flaw be to blame? By John McQuaid Staff writer One of the central mysteries emerging in the Hurricane Katrina disaster is why concrete floodwalls in three canals breached during the storm, causing much of the catastrophic flooding, while earthen hurricane levees surrounding the city remained intact. It probably will take months to investigate and make a conclusive determination about what happened, according to the Army Corps of Engineers. But two Louisiana State University scientists who have examined the breaches suggest that a structural flaw in the floodwalls might be to blame. “Why did we have no hurricane levee failures but five separate places with floodwall failures?” asked Joseph Suhayda, a retired LSU coastal engineer who examined the breaches last week. “That suggests there may be something about floodwalls that makes them more susceptible to failure. Did (the storm) exceed design conditions? What were the conditions? What about the construction?” Ivor Van Heerden, who uses computer models to study storm-surge dynamics for the LSU Hurricane Center, has said that fragmentary initial data indicate that Katrina’s storm-surge heights in Lake Pontchartrain would not have been high enough to top the canal walls and that a “catastrophic structural failure” occurred in the floodwalls. Corps project manager Al Naomi said that the Corps’ working theory is that the floodwalls were well-constructed, but once topped they gave way after water scoured their interior sides, wearing away their earth-packed bases. But he said some other problem could have caused the breaches. “They could have been overtopped. There could have been some structural failure. They could have been impacted by some type of debris,” Naomi said. “I don’t think it’s right to make some type of judgment now. It’s like presuming the reason for a plane crash without recovering the black box.” Officials long had warned about the danger of levees being topped by high water from a storm surge. Absent topping, floodwalls are supposed to remain intact. The floodwalls lining New Orleans canals consist of concrete sections attached to steel sheet pile drilled deep into the earth, fortified by a concrete and earthen base. The sections are joined with a flexible, waterproof substance. Floodwalls were breached in the 17th Street Canal, at two places in the London Avenue Canal, and at two places in the Industrial Canal, Suhayda said. Naomi said last week that one of the Industrial Canal breaches likely was caused by a loose barge that broke through it. Suhayda said that his inspection of the debris from the 17th Street Canal breach suggests the wall simply gave way. “It looks to have been laterally pushed, not scoured in back with dirt being removed in pieces,” he said. “You can see levee material, some distance pushed inside the floodwall area, like a bulldozer pushed it.” He suggested that because the walls failed in a few spots, the flaw may not be in the design but in the construction or materials…