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The 2011 Assiniboine River flood was caused by above average precipitation in Western Manitoba and Saskatchewan. This was a 1 in 300 year flood that affected much of Western Manitoba. The flooding in Manitoba was expected to mostly involve the 2011 Red River Flood but instead the more severe flooding was found on the Assiniboine in the west. ==Early signs== The 2011 flood really started in the fall of 2010 with several major rainfall events and generally wet conditions. Initially, it was predicted that the flood along the Assiniboine River would be similar to the flood of 1995.〔(【引用サイトリンク】url=http://www.rmofmacdonald.com/assets/flood/media%20bulletin%20-%2025%20march%202011.pdf )〕 During the winter of 2010–2011 the Shellmouth Reservoir was emptied in preparation, to store water for the coming spring flood. With more and more precitpitation, the estimates on the flood were revised upwards. The first major settlement to experience the floodwater was St. Lazare, Manitoba which was located near the confluence of the Assiniboine River and Qu'Appelle River. Dikes were built up to protect against the rising floodwater, but unfortunately some residences were not spared as their protective dikes were overwhelmed. The flood continued downstream, spilling over its banks and flooding campgrounds and fields in the flood plain. Brandon, Manitoba's second largest city, prepared well in advance of the anticipated flood building up both earthen dikes as well as sandbag/Hesco bastion dikes. After a heavy snowfall on April 29 and 30 over much of the Assiniboine River watershed the crest forecast for Brandon was revised upward well above the flood of 1976. The river peaked at about ,60% higher than the previous highest recorded peak of in 1923. The 2011 event is estimated to be a 1 in 300-year flood. Shortly thereafter a state of emergency was declared in Brandon as well as other municipalities across Manitoba. Premier Greg Selinger requested from Prime Minister Stephen Harper troops from the Canadian military to help with the flood fighting efforts. The last time the military was called in to help fight a flood in Manitoba was the 1997 Red River Flood. Downstream of Brandon, the Manitoba Government forecast that between 54000-56000 cu ft/s of water would enter into the Portage Diversion reservoir near Portage la Prairie.〔(【引用サイトリンク】url=http://news.gov.mb.ca/news/index.html?archive=month&item=11461 )〕 The capacity for the Portage Diversion channel, which drains into Lake Manitoba, is only approximately , which would mean that between 29000-31000 cu ft/s of water would flow toward communities such as Poplar Point, St. Francois Xavier, and Headingley, before joining with the Red River at The Forks.〔(【引用サイトリンク】url=http://www.gov.mb.ca/chc/press/top/2011/05/2011-05-09-180800-11448.html )〕 This amount of water would overwhelm the dikes downstream, along the Assiniboine River, which were only built to allow for a channel capacity of about 10,000-11,000 cu ft/s before spilling over. Otherwise breaching of dikes would occur.〔 On June 22, 2011 the city of Minot in North Dakota issued an evacuation of 12,000 residents due to the swollen Souris River that flows through the city. The Souris River starts in Saskatchewan and makes its way south across the border and then back north into Manitoba. Residents in Souris, Manitoba will be watching to see what happens. The Souris River then eventually joins up with the Assiniboine River past Brandon which could again raise water levels on the Assiniboine due to the swollen Souris and the possibility of Lake Manitoba raising up again. Preparations are under way for the communities along the Souris to raise dikes and evacuations have begun. The province has said it will push the limits of the flood protection again. 2011 Souris River flood 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「2011 Assiniboine River flood」の詳細全文を読む スポンサード リンク
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