Ice Jam Formation and Release Dynamics - Hay River, NWT

每年春季，河流决堤都会给加拿大许多河流周围的社区带来冰塞洪水的威胁。当融雪使河流膨胀，并突然抬起和打破冰盖时，就会发生破冰堵塞。冰块最初可能会随着融雪流沿着流动，但往往会变得拥挤--可能是在桥上，在河流的一个紧弯曲处，或在岛屿之间--当这种情况发生时，就形成了冰塞。水流被冰坝阻挡，水位可以以每分钟60到90厘米（2到3英尺）的速度上升，几乎没有任何预警。位于西北地区大奴湖南海岸的干草河镇就是这样一个社区;每年春天那里都会形成冰塞。近几十年来最严重的洪水发生在1963年。当地居民罗伊·法比安（Kátl 'odeeche第一民族的前酋长）在洪水发生时还是个男孩，他向我们讲述了一个可怕的故事，他从他家二楼的窗户乘船获救。他们拼命地划向灌木丛，当他回头看时，他看到一道水墙从水道里涌出来。他说，他看不到对面河岸上30英尺高的树，一旦堵塞形成，冰就堆积得很高。最近，2003年和2008年发生了严重洪灾，2005年、2007年和2009年发生了轻微洪灾。为了确保加拿大各地每年春季受到冰塞威胁的许多社区的人民和财产的安全，需要实用和可靠的河流冰塞洪水预报工具。为了开发这样的模型，我们需要研究冰塞行为，既要了解其复杂性，又要有必要的数据来测试我们的模型。由于其冰塞发生的倾向，以及对洪水预警系统的需求，干草河是进行此类科学研究的理想地点。在这个网站上的研究也使我们有机会直接帮助社区在他们的洪水预报工作每年春天。

Each year during the spring, river breakup brings the threat of ice jam floods to many of the communities across Canada that are situated around rivers. Breakup ice jams occur when snowmelt swells the stream, and lifts and breaks the ice cover suddenly. The ice pieces may initially be carried along with the snowmelt flow, but often become congested - perhaps at a bridge, at a tight bend in the river, or in amongst islands - and when this happens an ice jam is formed. The streamflow is blocked by this dam of ice, and water levels can rise at rates approaching 60 to 90 centimeters (2 to 3 feet) per minute, with virtually no advance warning. The Town of Hay River, situated on the south shore of Great Slave Lake in the Northwest Territories is one such community; ice jams form there every spring. The most extreme flood in recent decades occurred in 1963. Local resident Roy Fabian (former Chief of the Kátl`odeeche First Nation) was a boy at the time of the flood and recounted for us a terrifying story of being rescued by boat, from the second story window of his house. They paddled furiously towards the bush, and as he looked back, he saw a wall of water surging from the channel. He said he could not see 30 foot high trees on the opposite river bank the ice had piled so high once the jam formed. More recently, severe flooding occurred in 2003 and 2008, and minor flooding in 2005, 2007 and 2009. To ensure the safety and security of people and property in the many communities across Canada that are threatened by ice jams each spring, practical and reliable river ice jam flood forecasting tools are needed. To develop such models we need to study ice jam behaviour, both to understand its complexities, and to have the needed data to test our models. With its propensity for ice jam occurrence, and its need for flood warning systems, Hay River represents an ideal location for such scientific studies. Research at this site also affords us the opportunity to directly help the community in their flood forecasting efforts each spring.