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On 29 August 2005 there were over 50 failures of the levees and flood walls protecting New Orleans, Louisiana, and its suburbs following passage of Hurricane Katrina and landfall in Mississippi. The levee and flood wall failures caused flooding in 80% of New Orleans and all of St. Bernard Parish. Tens of billions of gallons of water spilled into vast areas of New Orleans, flooding over 100,000 homes and businesses. Responsibility for the design and construction of the levee system belongs to the United States Army Corps of Engineers; the responsibility of maintenance belongs to the local levee boards. The Corps hands components of the system over to the local levee boards upon completion. When Katrina struck in 2005, the project was between 60-90% complete.〔http://www.gao.gov/new.items/d051050t.pdf〕 Four major investigations were conducted by civil engineers and other experts in an attempt to identify the underlying reasons for the failure of the federal flood protection system. All concur that the primary cause of the flooding was inadequate design and construction by the Corps of Engineers. There were six major breaches in Orleans Parish: #Three major breaches occurred on the Industrial Canal: one on the northeast side near the junction with Gulf Intracoastal Waterway and two on the southeast side along the Lower Ninth Ward, between Florida Avenue and Claiborne Avenue. #On the west side of New Orleans, the 17th Street Canal levee breached below design specs on the New Orleans side near the Old Hammond Highway Bridge #The London Avenue Canal in the Gentilly neighborhood breached on both sides - on the west side near Robert E. Lee Boulevard and on the east near the Mirabeau Avenue Bridge Storm surge caused breaches in 20 places on the Mississippi River-Gulf Outlet Canal ("MR-GO") in Saint Bernard Parish, flooding the entire parish and the East Bank of Plaquemines Parish. ==Background== The original residents of 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 compacting and desiccation of the underlying organic soils. After the Great Mississippi Flood of 1927, Congress passed the Flood Control Act of 1928 which authorized the Corps of Engineers to design and construct flood control structures, along with levees, on the Mississippi River to protect populated areas from floods. 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.〔(Flood Control Act of 1928 on Mississippi Valley Division of USACE website )〕 It is instructive to note that, in addition, sovereign immunity was given to the Corps of Engineers under Section 3 of the Flood Control Act of 1928, which states “no liability of any kind would attach or rest upon the United States for any damage from or by floods or flood waters at any place, provided that if on any stretch of the banks of the Mississippi River it was impracticable to construct levees.” 33 U.S.C. § 702c. Section 702c is sometimes referred as “Section 3 of the act,” based on where it appears in the public law. Heavy flooding caused by Hurricane Betsy in 1965 brought concerns regarding flooding from hurricanes to the forefront. In response, the Congress passed the Flood Control Act of 1965 which mandated that henceforth, the Corps of Engineers is the agency responsible for design and construction of flood protection projects, to include those in Greater New Orleans. The local interests' role was maintenance once the projects were complete.〔(GAO Report on Lake Pontchartrain and Vicinity Hurricane Protection Project, September 2005 )〕 Also that year, Congress authorized the Lake Pontchartrain and Vicinity Hurricane Protection Project (LPVHPP) which reiterated the principle of local participation in federally funded projects. 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 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. In April 2007, the American Society of Civil Engineers called the flooding of New Orleans "the worst engineering catastrophe in US History."〔(The New Orleans Levees: The Worst Engineering Catastrophe in US History - What Went Wrong and Why )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2005 levee failures in Greater New Orleans」の詳細全文を読む スポンサード リンク
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