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:''This article covers the levee system and infrastructure repairs in New Orleans, Louisiana following Hurricane Katrina.'' Though Hurricane Katrina did not deal the city of New Orleans a direct hit on August 29, 2005, her storm surge precipitated catastrophic failures of the levees and flood walls. The Mississippi River Gulf Outlet ("MR-GO") breached its levees in approximately 15 places. The major levee breaches in the city include the 17th Street Canal levee, the London Avenue Canal, and the wide, navigable Industrial Canal, which left approximately 80% of the city flooded.〔Murphy, Verity. "(Fixing New Orleans' thin grey line )." ''BBC News.'' October 4, 2005.〕 While ownership, definition of requirements, operation and maintenance of the system belonged to the Orleans Levee Board, federal responsibility for New Orleans' flood protection design and construction belongs by federal mandate to the US Army Corps of Engineers. Flooding from the breaches put the majority of the city under water for days, in many places for weeks. The Corps made emergency repairs to breaches, as pumps worked at draining the city. Hurricane Rita brushed the city nearly a month later, causing reflooding of some areas, most significantly from water flowing through incompletely repaired levee breaches. ==Background== (詳細はdelta marsh, much of which sits below sea level. The city is surrounded by the Mississippi River to the south, Lake Pontchartrain to the north, and Lake Borgne to the east. Construction of the levees along the River began soon after the city was founded, and more extensive river levees were built as the city grew. The levees were originally designed to prevent damage caused by seasonal flooding. Today, the floodwalls atop the 17th Street and London Avenue Canals are used for drainage, to pump water from the city streets out to Lake Pontchartrain. These floodwalls are one foot (300 mm) wide at the top and widened to two feet (600 mm) at the base. The visible portion is a concrete cap on steel sheet pile that anchors to the wall. Sheet piles are interlocked steel columns, in this case at least 30 feet (10 m) long, with 6 to 10 feet (2 to 3 m) visible above ground; examinations afterward showed that some pilings were not as deep as specified. The wide, navigable Industrial Canal is used for shipping. The heavy flooding caused by Hurricane Betsy in 1965 brought concerns regarding flooding from hurricanes to the forefront. Congress removed responsibility from the state and mandated that the US Army Corps of Engineers have sole authority over the design and construction of the New Orleans area flood protection, although local cooperation was stipulated. This is spelled out in the Flood Control Act of 1965.〔http://www.fws.gov/habitatconservation/Omnibus/R&HA1965.pdf〕 Forty years later when Katrina struck, the flood protection was between 60-90% completed with an estimated completion date of 2015, despite the initial expectation of completion within thirteen years.〔http://www.gao.gov/new.items/d051050t.pdf〕 As of May 2005, work in Orleans Parish was certified as 90% complete, with "some work remaining" along the London Avenue Canals, and 70% complete in Jefferson Parish.〔 There were many predictions of hurricane risk in New Orleans before Hurricane Katrina in August, 2005.〔Wilson, Jim. "(New Orleans is Sinking )." ''Popular Mechanics.'' September 11, 2001.〕〔Fischetti, Mark. "(Drowning New Orleans )." ''Scientific American.'' October, 2001.〕〔Mooney, Chris. "(Thinking Big About Hurricanes )." ''The American Prospect.'' May 23, 2005.〕 In 2001, the ''Houston Chronicle'' published a story which predicted that a severe hurricane striking New Orleans, "would strand 250,000 people or more, and probably kill one of 10 left behind as the city drowned under of water. Thousands of refugees could land in Houston."〔Berger, Eric. "(Keeping its head above water: New Orleans faces doomsday scenario )." ''Houston Chronicle.'' December 1, 2001.〕 Many concerns also focused around the fact that the city's levee system was only designed for hurricanes of no greater intensity than category 3.〔Westerink, J.J.; Luettich, R.A. "(The Creeping Storm )." ''Civil Engineering Magazine.'' June, 2003.〕〔Laska, Shirley. "(What if Hurricane Ivan Had Not Missed New Orleans? )" ''Natural Hazards Observer.'' November 2, 2004.〕 As it turned out, Katrina was Category 3 when it made landfall and most of New Orleans experienced Category 1 or 2 strength winds. However, due to the slow moving nature of the storm in its pass over New Orleans, several floodwalls lining the shipping and drainage canals in New Orleans collapsed and the resulting flood water from Lake Ponchartrain inundated the city within the two days following the storm, causing costly damage to buildings and resulting in many deaths. Furthermore, the region's natural defenses, the surrounding marshland and the barrier islands, have been dwindling in recent years due to human interference.〔Bourne, Joel K. "(Gone with the Water )." ''National Geographic.'' October, 2004.〕 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「Civil engineering and infrastructure repair in New Orleans after Hurricane Katrina」の詳細全文を読む スポンサード リンク
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