New Orleans' levee failures were found to be primarily the result of system design flaws, combined with the lack of adequate maintenance. Those responsible for the conception, design, construction, and maintenance of the region's flood-control system apparently failed to pay sufficient attention to public safety, according to an investigation by the National Science Foundation.[114]
According to new modeling and field observations by a team from Louisiana State University, the Mississippi River Gulf Outlet (MRGO), a 200-meter (660 ft) wide canal designed to provide a shortcut from New Orleans to the Gulf of Mexico, helped provide a funnel for the storm surge, making it 20% higher and 100%-200% faster as it crashed into the city. St. Bernard Parish, one of the more devastated areas, lies just south of the MRGO. The Army Corps of Engineers disputes this causality and maintains Katrina would have overwhelmed the levees with or without the contributing effect of the MRGO.[115]
On April 5, 2006, months after independent investigators had demonstrated that levee failures were not caused by natural forces beyond intended design strength, Lieutenant General Carl Strock testified before the United States Senate Subcommittee on Energy and Water that "We have now concluded we had problems with the design of the structure."[116] He also testified that the U.S. Army Corps of Engineers did not know of this mechanism of failure prior to August 29, 2005. The claim of ignorance is refuted, however, by the National Science Foundation investigators hired by the Army Corps of Engineers, who point to a 1986 study by the Corps itself that such separations were possible in the I-wall design.[117]
Various conspiracy theories began floating around that the levees were in fact deliberately demolished. A number of New Orleans residents described hearing "explosions" coming from the Industrial Canal levee in the Lower 9th Ward before the floodwaters rushed in. A National Guard worker claims he was sworn to secrecy upon finding explosives residue at the site of the break.[118]
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