Predicting Dynamic River Ice Processes

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River ice is an important issue in Canada, as in many other northern countries. Contrary to the peaceful image that the typical mid-winter ice cover implies, river ice is actually comprised of a broad variety of dynamic processes, particularly during freeze-up and breakup, and these dynamic ice processes can cause significant problems. For example, in the fall as water temperatures cool to a few hundredths of a degree below zero, "frazil ice" particles form. These tiny ice particles are initially suspended throughout the river flow by fluid turbulence. However, frazil behaves in a very 'sticky' manner in this supecooled water and readily sticks to itself and many other objects. It can attach to 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. River ice can be equally problematic in spring. On rivers where the breakup is particularly dynamic, ice jams can form causing flooding and presenting a significant threat to human safety. It is important to be able to predict these, and other, dynamic ice processes so that we can plan the effective operations of water intakes, to avoid creating anchor ice problems (particularly in stream habitat restoration projects), and to provide the public with adequate warning of impending floods. However, at present, certain components of the numerical models available to predict river ice processes are actually highly empirical or not yet rigorously validated. Some ice properties (for example, suspended frazil concentrations) cannot yet even be measured. Therefore, we don't always know if the models are 'getting it right'. This research is focused on conducting field studies of a variety of dynamic river ice processes, aimed at advancing our knowledge and ability to implement more physically based numerical models, and to provide essential validation data to test these predictive models.