Frazil Ice Formation and Evolution

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Frazil ice particles are small, disc-shaped ice crystals that form in turbulent rivers once the water temperature has supercooled to a few hundredths of a degree below zero. Frazil ice particles are very adhesive in supercooled water and they readily stick to each other forming buoyant frazil flocs that rise to the surface where they form `frazil pans' which then accumulate to form a full ice cover. Frazil particles easily adhere to almost any surface, such as screens and trash racks on water intakes, cutting off the water supplies to municipalities, industries, and power plants. It can also stick to the river bed, building up "anchor ice", which can be very harmful to fish. For example, in small rivers, anchor ice can fill up the entire channel in a single night, inhibiting habitat access for juvenile fish or blocking the oxygen supply to eggs buried in the stream bed. Despite the importance of frazil ice to the river freeze-up process and the consequences of its formation, little is known about its generation, transport and evolution. One reason for this is our current inability to accurately measure suspended frazil concentrations and size distributions in rivers. The long-term goal of the proposed research is to develop accurate methods for monitoring and predicting the formation of frazil ice in rivers and its subsequent transport and evolution during freeze-up. My research group has developed a unique digital imaging system that is designed to be deployed underwater in rivers at freeze-up and we propose to use this new technology to make the first accurate measurements of frazil ice properties in three Alberta rivers. We also propose to continue developing a sonar based system that can be used to continuously monitor river ice processes. In addition to this we will continue investigating the properties of frazil ice in the laboratory using our unique frazil ice generation tank. The data that we collect will have a tremendous impact because it will allow us and others to critically assess the accuracy of and improve numerical river ice models. Frazil ice formation and evolution is the dominant river ice process during freeze-up and therefore improving our ability to accurately monitor and predict it in rivers will have a significant impact on the planning design, construction and operation of infrastructure built along rivers.**