Observations and Modelling of Freeze-up Processes in Rivers

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Tiny ice particles, called frazil, form in the turbulent portions of the flow in northern rivers when the water supercools to just below zero degrees. Virtually all forms of river ice originate from frazil and its formation and evolution are the dominant river ice processes during freeze-up. Frazil particles in supercooled water readily adhere to natural and man-made surfaces. They may stick to the bed, forming anchor ice, or to each other, creating flocs that ultimately become large slush balls at the surface, freeze together into `frazil pans,' and eventually form the ice cover. Numerical river ice models include algorithms for simulating freeze-up processes but their accuracy is unknown due to a lack of field data to compare with. Although progress has been made in recent years to develop accurate measurement techniques there is still a great need for additional field measurements. To address this need, I propose an ambitious program of field measurements designed to significantly increase our knowledge of key freeze-up processes, and to use the resulting data to assess the accuracy of the algorithms currently used to model these processes. The long-term goal of the proposed research is to improve our understanding of how river ice forms, and its impacts on river ecology, hydraulics, and geomorphology. The short-term objectives of the proposed research program are to:    (1)Continue investigating the generation, transport, and fate of suspended frazil ice in rivers    (2)Investigate the properties of anchor ice and its impact on the ecology and hydraulics of rivers.    (3)Determine the impact of rafting of sediment by anchor ice on the sediment budget of rivers.    (4)Assess the ability of river ice process models to accurately model freeze-up. Three PhD and two MSc students will collaborate on the proposed research. The students will receive training on the use of a wide variety of sophisticated field instrumentation, advanced data processing methods and numerical modelling. Field measurements will be conducted over multiple winters on two rivers. River1D, a river ice processes model, will be applied to both rivers and its accuracy simulating freeze-up processes will be assessed by comparing model predictions to field measurements. The MSc students will gather digital images of surface ice conditions on the Peace River and analyze them using machine learning techniques. Their goal is to obtain accurate estimates of the amount of sediment transported by released anchor ice pans. Improving our ability to accurately monitor and predict freeze-up processes in rivers will have a significant impact on the planning, design, construction and operation of infrastructure built along rivers. It will also enhance our ability to assess the environmental impacts of cold region projects and more accurately assess the impact of climate change on freeze-up processes in northern rivers.