2005 Levee Failures in Greater New Orleans - Background

Background

See also: Drainage in New Orleans and Hurricane preparedness for New Orleans

The original residents of Greater New Orleans settled on the high ground along the Mississippi River. Later developments eventually extended to nearby Lake Pontchartrain, built upon fill to bring them above the average lake level. Navigable commercial waterways extended from the lake to downtown. After 1940, the state decided to close those waterways following the completion of a new Industrial Canal for waterborne commerce. Closure of the waterways resulted in a drastic lowering of the water table by the city's drainage system, causing some areas to settle by up to 8 feet (2 m) due to the consolidation of the underlying organic soils. After 1965, the Corps of Engineers built a levee system around a much larger geographic footprint that included previous marshland and swamp. The average elevation of the city is between 1 to 2 feet (0.61 m) below sea level. There are no residential areas of the city that are currently more than 10 feet (3 m) below sea level.

After the Great Mississippi Flood of 1927, the Congress mandated the Corps of Engineers as the federal agency responsible for design and construction of flood protection projects, to include those in Greater New Orleans. It also affirmed the principle of local participation in federally funded projects but acknowledged that the $292 million already spent by local interests was sufficient to cover local participatory costs. It also required that local interests had to agree to be responsible for maintenance of any proposed levees before the projects would be initiated.

The heavy flooding caused by Hurricane Betsy in 1965 brought concerns regarding flooding from hurricanes to the forefront. That year, through enactment of the Flood Control Act of 1965 (FCA 1965) Congress authorized the Pontchartrain Hurricane Protection Project. FCA 1965 reiterated the principle of local participation in federally funded projects. The local interests' role was maintenance once the work was complete. Although federally authorized, it was a joint federal, state, and local effort. Almost from the start, the design was impacted by changes due to technical issues, environmental concerns, legal challenges, and local opposition by those opposed to the project. The project was initially estimated to take 13 years, but when Katrina struck in 2005, almost 40 years later, the project was only 60–90% complete with a revised projected completion date of 2015.

On August 29, 2005, flood walls and levees catastrophically failed throughout the metro area. Some – the extent of which is disputed – collapsed well below design thresholds (17th Street and London Canals). Others collapsed after a brief period of overtopping (Industrial Canal) caused "scouring" or erosion of the earthen levee walls – a design flaw. In April 2007, the American Society of Civil Engineers called the flooding of New Orleans "the worst engineering catastrophe in US History."