New Orleans' location on the Gulf Coast with water on three sides and below-sea-level terrain makes this densely populated section of Louisiana highly susceptible to flooding from hurricane storm surges. New Orleans' flooding threats are not only from the coast but also from the Mississippi River and rainfall that gets trapped in the city, known as stormwater . The system of levees and floodwalls around the city is designed to provide a specified level of protection from riverine and coastal flooding; where as, massive pumps and drainage canals that flow into Lake Pontchartrain manage the city's stormwater. Local levee districts maintain the hurricane levees and floodwalls that were built largely by the U.S. Army Corps of Engineers 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 Sewerage and Water Board of New Orleans is responsible for the city's stormwater management infrastructure. Breaches of the floodwalls protecting New Orleans during Hurricane Katrina were the major contributor to 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 to reliably perform has many stakeholders' speculating about the causes of the failures. A question central to many of the investigations into Katrina-related damage and of concern in rebuilding efforts is: were the levees and floodwalls breached because their design was exceeded, or did they fail due to faulty design, construction, or maintenance? To answer these questions, evidence has and continues to be collected on numerous fronts, including evidence of the height of the storm surge in various locations, and how the levees and floodwalls performed. Technical experts from universities, professional engineering organizations, and the Corps are using this evidence to model and explain the performance of New Orleans' hurricane protection system. The findings are likely to shape not only the future design of the 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. Moreover, the findings may improve understanding and change perceptions of the level of flood protection and risk in other U.S. cities. Understanding why New Orleans' hurricane protection system failed is essential for moving beyond simply making repairs to damaged levees and floodwalls. Knowing why the floodwalls failed is central to assessing the city's vulnerability to storm surge flooding and deciding on how to most effectively combine approaches for managing flood risk during rebuilding efforts (e.g., investing in coastal wetlands loss and hurricane protection infrastructure, requiring flood-proofing in certain areas, and mapping areas for the federal flood insurance program). Nonetheless in order to be prepared for the 2006 hurricane season, the Corps is having to proceed with immediate repairs of damaged levees and floodwalls using available information and integrating new information as it is available. One of the causes of failure being discussed is a poor or inadequate design for protecting the city from a Category 3 hurricane. The original project design was to control storm surge flowing into water bodies near downtown by building inlet barriers and canal floodgates. 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 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 the 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 discusses the evolution in the project's design, 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 the floodwall failures in downtown New Orleans' during Hurricane Katrina: (1) the shift from the barriers at the inlets to Lake Pontchartrain to higher levees along the lake; 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 report includes an appendix summarizing the federal funding history for the Lake Pontchartrain project. The analysis contained herein is based on currently available information and is limited in scope. Although there were more than a dozen breaches and many other segments of damaged levees and floodwalls in the greater New Orleans area and numerous in other coastal Louisiana parishes, the four breaches (see Figure 1 ) of the Lake Pontchartrain project that have received the greatest attention due to their impact on downtown New Orleans were the following: a breach of the 17 th Street Canal floodwall; two breaches of the London Avenue Canal floodwall; and a breach of the western flank of the Inner Harbor Navigation Canal (IHNC, also known as the Industrial Canal) floodwall. Flooding due to overtopping of city's levees and floodwalls was predicted for storm surges from a storm stronger than a Category 3 hurricane passing close to the New Orleans region. Extensive overtopping may cause a levee or floodwall breach. Breaching in urban areas often produces catastrophic damage. Hurricane Katrina had weakened from a Category 5 storm to a Category 4 storm by the time passed east of New Orleans. Overtopping was the cause of much of the flooding and most of the breaches and damage to the hurricane protection infrastructure in coastal Louisiana. However, overtopping does not appear to have caused much of the flooding and some of the breaches in downtown New Orleans. A November 2005 preliminary analysis of the performance of New Orleans' hurricane protection system by technical expert teams from the University of California at Berkeley and the American Society of Civil Engineers indicate the method of failures at the breaches in downtown New Orleans. The teams' preliminary evidence suggests that breaches along the 17 th Street and London Avenue canals occurred before the floodwalls were overtopped; that is, these floodwalls failed before their design was exceeded. The immediate and underlying causes of these breaches (i.e., what led to the failures) are the subject of conjecture; hypotheses range from exceeded design, poor design, faulty construction, maintenance issues, incomplete construction due to the level of construction appropriations (see the Appendix for information on the project's federal funding), and modifications to the project's original design. The Corps has initiated a forensic investigation of the floodwall breaches; the results are expected in June 2006. According to the teams' preliminary analysis, the combined storm surges from several direction along the IHNC and the Mississippi River Gulf Outlet (MRGO) overtopped the IHNC and MRGO. Congress authorized the Corps to protect New Orleans from the rough equivalent of a Category 3 storm when it authorized the Lake Pontchartrain and Vicinity Hurricane Protection Project in October1965. The project consists of levees and floodwalls, most of which were constructed by the Corps and cost-shared by the federal government and local levee districts. The Orleans Parish segments of the Lake Pontchartrain  project, which encompass downtown New Orleans, were 90% complete as of May 2005. The total cost for the Lake Pontchartrain and Vicinity project is $738 million, with the federal responsibility $528 million. Federal allocations totaled $457 million through FY2005, leaving around $70 million to complete federal funding. The original design of the Lake Pontchartrain project was sent to Congress in July 1965. The project was designed to protect the city from a standard hurricane for the region, which was roughly equivalent to a Category 3 hurricane on the Saffir-Simpson Scale. The standard hurricane was defined as high sustained wind speeds reasonably characteristic for a specified coastal location. Reasonably characteristic was defined as only a few hurricanes on record over the general region had been recorded to have more extreme wind and other meteorological characteristics. The standard hurricane was determined by the U.S. Weather Service. Two months later in September 1965, Hurricane Betsy, a Category 3 hurricane, struck Louisiana's coast, causing damage in New Orleans. Congress authorized construction of the Lake Pontchartrain project in the Flood Control Act of 1965, enacted in October 1965. Modifications to the authorization have been made in subsequent legislation. Since that original design, there have been two major developments in the project relevant to current investigations into the floodwall failures: (1) the shift from the barriers at the inlets to Lake Pontchartrain to higher levees along the lake; 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. These two decisions are discussed below. The original July 1965 Lake Pontchartrain project design consisted of the Barrier Plan for constructing inlet barriers at Lake Pontchartrain's three main tidal entrances as well as levees and floodwalls for surge protection. The barriers generally would remain open and allow for navigation, and would close during coastal storms to reduce storm surges from entering the lake.