River ice breakup flood forecasting

春季径流、仲冬融化和水峰作业可能会引发河冰破裂，由于其对经济和生态的影响，这对加拿大的河流来说是一个至关重要的事件。分崩期的特点是频繁的冰堵事件，这可能导致严重且难以预测的洪水；此外，当冰堵形成时，可能会造成物理障碍，阻碍航行。当冰塞释放时，它们会产生破坏性的高速水波和冰流，可能会破坏基础设施，导致堤岸和河床侵蚀，并危及甚至沉没航运。由于冰塞带来的风险，经常需要修改水力调峰作业，以避免触发它们的形成和释放，从而限制水电生产。冰堵事件可能会对河流生态系统造成不利影响，但在某些情况下，也可能为河流系统(例如麦肯齐河三角洲)提供必要的补给。由于所有这些原因，了解河流破裂和冰堵现象并能够更准确地预测它们的发生是可取的。挑战在于，冰的存在与动态流动以各种方式相互作用，使得预测这些事件变得非常困难。*这项研究计划旨在解决目前阻碍我们预测河冰破裂期间冰塞洪水的几个关键问题，并将增进我们对复杂破裂过程的了解。将使用数学建模技术，并辅之以现有的实地数据。首先，将调查影响河流破裂和相关冰塞事件的时间、频率和严重程度的主要因素的影响，包括冰情、航道形态、气象条件和水流条件。第二，将开发新的模式。特别是对于河流三角洲地区这样的多渠道系统，那里往往会发生冰塞，现有的模型在操作上是不可行的。一维模型只模拟单一河道的水流，在二维上测量或模拟延伸的河段是不现实的。因此，本研究开发的模型将提供一种独特的操作工具，允许调查多通道系统中由冰干扰引起的各种问题。这项研究还将提供一个具有可操作性的预测模型，可以可靠地预测冰堵洪水的预期严重程度。这样的模型将允许更早地预测洪水，从而允许更快地疏散受影响的社区，这将立即使毗邻经历冰堵洪水的河流的北部社区受益。总体而言，拟议的计划将产生一个更准确和更全面的河冰模型，并将我们推向可靠地预测天然河流中的冰塞形成和释放事件的最终目标，以及在河流决口之前改进洪水风险的预测。

River ice breakup can be instigated by spring runoff, mid-winter thaws, and hydro-peaking operations, and is a crucial event on Canadian rivers because of its economic and ecological impacts. The breakup period features frequent ice jam events which can result in severe and hard-to-predict flooding; further, when formed in place, ice jams can create physical barriers that impede navigation. When ice jams release, they can produce destructive high-speed water waves and ice runs that can damage infrastructure, cause bank and bed erosion, and endanger or even sink shipping. Because of the risks posed by ice jams, hydro-peaking operations often need to be modified to avoid triggering their formation and release, thus limiting hydro-power production. Ice jam events may adversely impact river ecosystems but in some cases can also provide essential replenishment to the river systems (e.g. Mackenzie River Delta). For all these reasons, it is therefore desirable to understand river breakup and ice jam phenomena and to be able to predict their occurrence with greater accuracy. The challenge is that the presence of ice, interacting with the dynamic flow in various ways, makes forecasting these events very difficult. ***This research program aims to address several key issues that are currently impeding our ability to forecast ice jam floods during river ice breakup, and will advance our knowledge of complex breakup processes. Mathematical modelling techniques will be used, complemented with existing field data. First, the effects of major factors that affect the timing, frequency, and severity of river breakup and associated ice jam events will be investigated, including ice conditions, channel morphology, meteorological conditions, and flow conditions. Second, new model will be developed. Particularly for multi-channel systems such as river delta areas, where ice jamming tends to occur, existing models are not operationally viable. One-dimensional models only simulate single channel flows, and it is not practical to measure or model an extended reach in two dimensions. The model developed in this research will therefore provide a unique operational tool that allows investigation of various problems caused by ice jamming in multi-channel systems. The research will also provide a forecasting model that is operationally practical and can reliably predict the anticipated severity of ice jam flooding. Such a model will allow earlier predictions of flooding and hence permit speedier evacuation of affected communities, which will immediately benefit northern communities situated next to rivers that experience ice jam flooding. Overall, the proposed program will produce a more accurate and comprehensive river ice model and move us towards the ultimate goals of reliable prediction of ice jam formation and release events in natural rivers and improved projections of flood risk in advance of river breakup.**