River ice breakup flood forecasting

春季径流、冬季中期解冻和水力峰值操作都可能引发河冰破裂，这对加拿大河流来说是一个至关重要的事件，因为它对经济和生态都有影响。破裂期的特征是频繁的冰堵塞事件，可能导致严重且难以预测的洪水；此外，在适当的地方形成冰塞会造成阻碍航行的物理障碍。当冰塞释放时，它们会产生破坏性的高速水波和冰流，这会破坏基础设施，造成河岸和河床侵蚀，危及甚至沉没航运。由于冰塞带来的风险，水力调峰操作通常需要进行修改，以避免引发冰塞的形成和释放，从而限制水力发电。冰塞事件可能对河流生态系统产生不利影响，但在某些情况下也可以为河流系统提供必要的补充（例如麦肯齐河三角洲）。由于所有这些原因，因此了解河流破裂和冰塞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，以各种方式与动态水流相互作用，使得预测这些事件变得非常困难。

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.