Overestimated the Ability of Their Levee Systems. A damning new report commissioned by the Louisiana Department of Transportation and Development has found the U.S. Army Corps of Engineers (USACE) grossly overestimated the ability of their levee systems to protect New Orleans in the face of strong storms. A wide range of miscalculations and oversights by the Corps, says the report, led to the failure of the levees during Hurricane Katrina in 2005. In addition, the report concludes that the system today remains insufficient to protect the city against major storm surges.
The cadre of scientists and engineers, known as “Team Louisiana,” was led by Ivor van Heerden, director of the LSU Center for the Study of Public Health Impacts of Hurricanes. The highly anticipated, nearly 500-page report, offers a slew of data and evidence related to the failure of several federal levee systems, including those on the east and west banks of the Industrial Canal, east and west banks of the London Avenue Canal, the east bank of the 17th Street Canal, the north bank of the Gulf Intracoastal Waterway (GIWW), and the west bank of the Mississippi River Gulf Outlet (MRGO).
Among the criticisms of the Corps’ levee systems:
- The Greater New Orleans Hurricane Protection System (GNO HPS) was not properly conceived, based on the 1965 Congressional mandate that it must defend against “the most severe combination of meteorological conditions reasonably expected.” The report said that the initial meteorological and oceanographic analysis was “known to be obsolete by 1972.” Among other miscalculations, the maximum potential sustained wind speed was underestimated by 20 percent, which scientists said could have led to a 40 percent underestimation of surge elevation levels.
- The levees were built too low by a measure of one to two feet because of Corps miscalculations about New Orleans’ elevation, which actually sinks over time. The report said the Corps engineers used outdated information in the construction and failed to account for a subsidence (sinking of ground) rate of three to four feet per 100 years, a fact that had been established decades ago.
- The Corps did not “follow existing engineering practice and USACE guidance for construction of levees and floodwalls.” The report claims that the Corps did not properly account for soil strength and erosion as well as underseepage.
- The creation of the MRGO navigational canal compromised levee-system performance. Team Louisiana said that MRGO and the GIWW “provide efficient conduits to funnel surge into the heart of New Orleans.” They say that surge elevations were higher and rose more quickly because of these waterways.
- The levee system was not properly maintained and operated “to assure the required level of protection through time.” In fact, the report says, quite bluntly: “The GNO HPS was managed like a circa 1965 flood control museum.”
Provides a Substantially Lower Level of Protection
Perhaps most critically, the report determined that the Hurricane Protection System “still provides a substantially lower level of protection than that originally authorized in 1965.” The report also says, “It is evidence of how pervasively under-built the system was that it has cost as much after Katrina to repair the GNO HPS to a marginally stable pre-storm condition as was spent in the previous 40 years.”
Tellingly, the authors also felt the need to add the following passage in their executive summary: “One way to look at the Katrina event is as a catastrophic natural disaster, and, with respect to the magnitude of the storm surge, it was. This approach tends, however, to minimize the engineering contribution to the direct and indirect loss of as many as 1,500 Louisiana residents.”