Levee Report Jibes With Early Speculation

That weak soils, large storm surges and overtopped levees played key roles in the flooding of New Orleans during Hurricane Katrina are well-known hypotheses. On Friday, a preliminary report by the Army Corps of Engineers concurred.

In the report, investigators agreed with many of the early findings of outside technical experts, including a team at UC Berkeley funded by the National Science Foundation and a team sponsored by the American Society of Civil Engineers.

The early conclusions of those groups were that levees in New Orleans failed because of weak foundations that could not sustain the force of hurricane surges that moved up the city’s canal system, and that levees to the eastern flank of the city were too small and weak to endure even more-powerful surges.

Although the corps report does not discuss whether defects played a role in the failures, it does lay out an exhaustive agenda over the next six months for examining precisely the types of storm forces that occurred and determining exactly why the levees failed.

The investigation will include a corps expert and an outside expert in every technical area, an arrangement intended to ensure a measure of independence. The teams include, for example, specialists in hurricane surges from the University of Notre Dame and in geologic subsidence from the National Geodetic Survey.

“There is a lot of speculation that is natural in a situation like this,” said Lewis “Ed” Link, the University of Maryland levee expert who is leading the corps’ investigation, which is officially called the Interagency Performance Evaluation Task Force, or IPET.

Link, who spent most of his career in the corps, said that his teams would go through rigorous models of the storm forces and that they had already started to build computerized models of the system that would be analyzed on supercomputers. In addition, the team is conducting extensive field examination, including efforts to resolve uncertainty about how the levees were built.

Link said the team planned to extract steel sheet piles Tuesday from the 17th Street levee, which failed catastrophically. In recent months, experts have found discrepancies in Army paperwork about the depth of those pilings.

Link also said it was increasingly clear that Katrina was a “large” hurricane that very likely exceeded the forces that were expected in the corps’ original design, at least in some areas.

In making that early judgment, Link left open the possibility that the levees did not fail prematurely but simply suffered more punishment from high water and battering waves than designers had anticipated.

Many outside experts say there is compelling evidence that the levee system should have performed better and that design compromises over the last two decades left the system weak.

Though he would not speculate about defects in the levees, Link did say that the work of the Berkeley team and the American Society of Civil Engineers had been “very helpful.” The interim report concludes that the groups’ work is an “excellent synopsis.”

Raymond Seed, the Berkeley professor heading the National Science Foundation investigation, said Friday that he had not read the interim report, but that the fact that the corps had issued it was a positive breakthrough.

Over the last few months, Seed has criticized the corps’ early efforts after Katrina, saying that the organization was withholding information and making technical errors in repairing the levees.