NEW ORLEANS -- The Army Corps of Engineers acknowledged yesterday that design defects in the levees protecting New Orleans caused the majority of flooding during Hurricane Katrina and that the disaster will almost certainly trigger reforms in how the federal government protects the American public.
The Corps said that its 40-year effort to construct a hurricane protection system for the region of southern Louisiana had resulted in a set of piecemeal projects that "was a system in name only," a recognition that a wide range of errors, weak links and incomplete construction was at the heart of the massive damage that occurred on Aug. 29.
The Corps released a 7,000-page investigation report that is carefully worded and written in the language of government engineers, but delivers a stunning set of findings about errors made in the design of storm walls and earthen levees that failed during Katrina.
The report found that four major breaches of I-walls, a type of concrete storm wall that sits on top of an earthen levee, caused 65 percent of the flooding in the greater New Orleans area.
Although the report's executive summary never uses the words design defect, Corps officials said they now accept that their work had shortcomings and errors that were responsible in large part for the disaster.
"We do take accountability," Lt. Gen. Carl Strock, commander and chief engineer of the Corps, said at a press conference in a meeting room of a downtown New Orleans hotel, attended by five Army generals, the federal coordinator for Gulf Coast reconstruction and an assistant Army secretary.
The Corps, Strock said, "is deeply saddened and enormously troubled," by the finding.
Strock said every section of I-walls will eventually have to be replaced, because they proved ineffective during Katrina. The four breaches occurred when storm waters were still several feet below the tops of the walls, meaning they had failed well below the maximum forces they had been designed to withstand.
The report also puts in the historical record a formal acknowledgment of the scope of the disaster, which killed 1,293.
"The flooding caused a breakdown in New Orleans' social structure, a loss of cultural heritage and drastically altered the physical, economic, political, social and psychological character of the area," it said. "These impacts are unprecedented in their social consequence and unparalleled in the modern era of the United States."
While many of the technical findings had been released earlier in preliminary reports by the Corps, the report contains a large amount of new information:
Southern Louisiana is sinking much faster than generally recognized, and levees were at substantially lower elevations relative to sea level than they were designed to be. In some cases, levees were two feet below their designed elevations. Moreover, the Corps deliberately decided not to re-examine the problem, even as other federal agencies were recognizing the problem.
The city's pumping system, which provides the only way to remove water from a city below sea level, was not designed to operate during a major storm, and the impact of the flooding could have been reduced if the city had not lost its ability to pump water after Katrina. Because most of the region's pumps were inundated by the flood, it took 53 days to pump out the city, allowing the floodwaters to saturate and destroy structures.
Twenty-five percent of all the housing units in southern Louisiana were destroyed by Katrina. In New Orleans, the proportion is believed to be even higher.
Strock said the repaired sections of levees are now the strongest parts of the system. The repairs were supposed to be completed by June 1 but are behind schedule by about two months. The enormous undertaking required heavy construction work on 169 miles of damaged or destroyed levees.
Although the breaches caused most of the flooding, a significant part of the Katrina damage occurred because the storm was larger than the system was designed to resist. While wind speeds had dropped sharply by the time the hurricane hit New Orleans, its power over the Gulf of Mexico had created the largest ocean surge to ever hit the North American continent, the report said.
Ralph Vartabedian writes for the Los Angeles Times.