Big Easy Levee Design: Proposed Improvements to the Existing 17th Street and London Avenue Canal Levees

On the morning of Monday, August 29, 2005, Hurricane Katrina hit the city of New Orleans, Louisiana causing numerous levee failures. In the Jefferson and Orleans Parishes one levee failures occurred on the east side of the 17th Street Canal and two levee failures occurred on the London Avenue Canal - one each on the west and east sides. All of the failures occurred in section of the levee where I-Walls were installed for parallel flood protection. Because of their location, these failures were particularly devastating to Orleans Parish. Several feet of water covered nearly all of Orleans Parish for weeks after the hurricane. The 17th Street, Orleans and London Avenue Outfall Canals carry stormwater from pumping stations located in Orleans and Jefferson Parish north, discharging this water into Lake Pontchartrain. As with most failures, a combination of circumstances caused these events and these failures have been studied in great detail in the last two and a half years. However, these levees, which have a combined length of over 13 miles, must still protect those living in Orleans and Jefferson Parish. Starting with the knowledge of the existing levee and flood wall designs and an improved understanding of the underlying geotechnical conditions at these three canal locations, this paper outlines the current design alternatives being considered for improving the factor of safety for water elevations of 6, 8 and 10 feet (NAVD) for these structures. The alternatives currently being considered include: (1) New I-Wall construction (2) New T-Wall construction (3) Additional, but unproven, methods such as constructing a berm on the protected side of the levees, cutoff walls, and drains There are advantages and disadvantages to each of these alternatives, including significant cost differentials, performance during flood and hurricane events, land purchase, condemnation and demolition of existing structures, constructability concerns, urban construction environment, and so on. This paper discusses the existing conditions of the levees, the investigations and analyses performed, the advantages and disadvantages of the design alternatives, and the recommend design for improving these structures. 15 pp., 11 figures, 13 references.