Decades of mistakes – some as basic as not knowing the elevation of New Orleans – led the U.S. Army Corps of Engineers to believe its levees and floodwalls would protect the city from a storm as strong as Hurricane Katrina, a report released March 21 concludes.
The corps used obsolete research to design flood-control structures that were built too low and improperly maintained, a group of engineers and storm researchers called Team Louisiana said in its 475-page report. The report was commissioned by the state Department of Transportation and Development.
The system was intended to be strong enough to handle a Category 3 hurricane like Katrina, which devastated New Orleans when levees broke.
Two major studies last year looked at the engineering problems that caused the 2005 breaches, but the new study also closely examines whether the problems could have been foreseen when the flood-control system was created.
The report said the errors date to the original plans in 1965, which relied on land height measurements from 1929. Because the city had sunk over the years, the plans called for levees that were 1 to 2 feet too low.
“This mistake was locked in” for continuing construction by a policy adopted in 1985, even though scientists knew how fast New Orleans was sinking, the report said. By the time Katrina hit, the levees were as much as 5 feet too low.
The report also said the corps never used a storm surge model released in 1979 by the National Hurricane Center. “If they had, they would have realized that their levee system wasn’t high enough for a Category 3 storm at all,” said team leader Ivor van Heerden, a Louisiana State University professor, deputy director of the LSU Hurricane Center and a corps critic.
Additionally, he said the corps ignored its own models that suggested that the Mississippi River Gulf Outlet, a navigation channel completed in the early 1960s, would funnel storm surge into St. Bernard Parish and New Orleans.
The corps also should have known two canals would fail when water levels reached 10 feet. Van Heerden said that “a back-of-the-envelope calculation” would have alerted engineers to a problem with one of the canals, and that a soil strength analysis available since the 1950s would have highlighted flaws in the other.
The corps was preparing a response, spokesman John Hall said.
Van Heerden said almost all the problems could have been avoided if independent engineers had reviewed the corps’ plans before construction started.
Before Katrina struck, he said, he and fellow researchers had found sagging levees. He enlisted his students to ask the corps about them, and the agency responded by saying “‘These were federal levees built to federal standards and they’re not going to fail,”’ he said.
The report recommended an independent planning process for hurricane protection, and an independent, bipartisan panel similar to the Sept. 11 Commission to investigate why levees failed. The corps is expected to release a study soon tracing the decision-making process.
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