Three Independent Investigation into New Orleans’ hurricane protection system reveals a human role in all three of the major floodwall failures that left 100,000 homes underwater and Louisiana's approximately 1,000 hurricane deaths. The evidence presented implicates design flaws in the failures of two floodwalls near Lake Pontchartrain, designed and built by the U.S. Army Corp of Engineers to aid their mission of protecting the city from hurricanes, which collapsed when weakened soils beneath them became saturated and began to slide. The findings suggest that the Mississippi River Gulf Outlet, also built by the U.S. Army Corps of Engineers, helped amplify and intensify Katrina's initial surge, contributing to a third floodwall collapse on the east side of town.
The independent investigators believe the floodwalls themselves were the problem in the cases of the 17th Street and London Avenue canals, the two canals near Lake Pontchartrain. The floodwalls were built on bad soil. As early as the 1980’s, trouble was detected 20 feet below the when soil tests revealed a thick layer of peat--spongy, organic soil that is soft and highly compressible when dry but very weak when saturated with water. Nothing was done then. And in 1994, a now-defunct a New Orleans firm involved in levee construction claimed that floodwall sections were failing to line up properly because of unstable soils in court documents. An administrative law judge dismissed the complaint on technical grounds without specifically addressing the allegations about weak soils.
The Mississippi River Gulf Outlet, a larger dirt-moving project than the Panama Canal created in the 1960’s, acts as a navigation shortcut to the Port of New Orleans and important to the large port industry lobby. It’s potentially negative impact was know prior to Hurricane Katrina. Three months before Katrina, Hassan Mashriqui, a storm surge expert at LSU's Hurricane Center, told a room of emergency managers that the outlet was a "critical and fundamental flaw" in the Corps' hurricane defenses, a "Trojan Horse" that could amplify storm surges 20 to 40 percent as the outlet amounted to a funnel that would accelerate and enlarge any storm surges headed for the city's levees. Using a supercomputer model after Katrina, Mashriqui concluded:
"Without MRGO [Mississippi River Gulf Outlet], the flooding would have been much less…The levees might have overtopped, but they wouldn't have been washed away."
When a federal agency, like the US Army Corp of Engineers, is responsible for ensuring the citizenries protection from natural disasters, it is vital that they don’t create non-natural disasters.