Report raises questions on New Orleans levees

WASHINGTON – The force of surging high water from Hurricane Katrina bent back a key New Orleans flood wall and splintered its foundation, an investigating panel said Friday in a report that sheds new light on the cause of the city’s flooding while raising questions about the safety of the city’s surviving levees.

The report contradicted earlier views about why the 17th Street Canal flood wall collapsed, but it also said that the failures were “not anticipated” by the levees’ designers and that the system did not perform as intended. A 450-foot section of the flood wall near Lake Pontchartrain collapsed Aug. 29 without ever being overtopped by Katrina’s storm surge, according to the panel, which was appointed by the Army Corps of Engineers.

Army Corps officials said the findings had prompted an immediate reassessment of ongoing efforts to rebuild 169 miles of Katrina-damaged levees. “We are incorporating the information into our current repairs,” said Col. Lewis Setliff, who heads the rebuilding effort.

The collapse of the 17th Street flood wall left much of central New Orleans under water. The wall, a concrete structure that sits atop an earthen levee, was designed by the Corps.

Previous studies by independent analysts pointed to weak, peatlike soils beneath the flood walls as the primary reason for the collapse. Friday’s report by the Interagency Performance Evaluation Task Force also implicated weak soils. But the panel said that was only one of several factors in an unusual, top-to-bottom cleaving of the levee that occurred hours after Katrina hit.