Lanterna Rally

Author: Nicole T. Carter

Publisher:

Published: 2005

Total Pages: 15

ISBN-13:

Breaches of the floodwalls protecting New Orleans during Hurricane Katrina caused significant flooding in many areas of downtown. Although most of the levee breaches in coastal Louisiana were the result of the storm's surge flowing over levees, preliminary evidence suggests that three major breaches in downtown New Orleans occurred prior to the floodwalls being overtopped; that is, the floodwalls failed before their design was exceeded. The failure of these floodwalls has many stakeholders' speculating about the causes of the failures, the reliability of the system of levees and floodwalls, and future options for protecting the city. One cause of failure being discussed is a poor or inadequate design for protecting the city from a Category 3 hurricane. The original design for the city's hurricane protection infrastructure was to control storm surge flowing into water bodies near downtown by building inlet barriers and canal floodgates. The U.S. Army Corps of Engineers was responsible for designing and building much of the infrastructure as part of its Lake Pontchartrain and Vicinity Hurricane Protection Project to protect New Orleans and the surrounding parishes from a Category 3 hurricane; the local levee districts shared 30% of the construction costs and maintained the infrastructure. During the project's construction which began with authorization in 1965 and was ongoing when Hurricane Katrina made landfall, numerous factors contributed to changing the design of how to protect the city (e.g., including local environmental concerns, changing cost estimates, local flood protection preferences, and litigation); the final design attempted to reduce hurricane related flooding in the city by increasing the height of levees and floodwalls, in lieu of the barriers and floodgates. The findings of ongoing investigations about the causes of the floodwall failures are likely to shape not only the future design of the city's hurricane protection system but also plans for rebuilding sections of the city and perspectives on the federal role and responsibility in the city's rebuilding efforts. This report documents the evolution in the design of the Lake Pontchartrain project, with specific reference to how and by whom design decisions were made. The focus is on two major design developments relevant to the current investigations into floodwall failures in downtown New Orleans: (1) the shift from barriers at Lake Pontchartrain's inlets to higher levees along the lakeshore; and (2) the shift from floodgates at the mouth of the city's stormwater outfall canals that drain into Lake Pontchartrain to higher floodwalls along the length of the canals. The Corps' decision in the mid-1980s to recommend higher levees instead of the inlet barriers it had recommended in 1965 was shaped by multiple factors, including environmental litigation, project economics, and local preferences. The Corps preferred floodgates to floodwalls along the Orleans Avenue and London Avenue canals. The decision to not build floodgates, and instead build floodwalls along the canals, was made by local project sponsors. The original design and the final design were intended to provide the same level of protection, i.e., protection from the rough equivalent of a Category 3 storm surge. This report will be updated as events warrant.