Investigation of river ice cover formation processes at freeze-up
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Date
2019
Authors
Wazney, Lucas
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Abstract
The formation of a river ice cover at freeze-up has several implications on society. In fast flowing rivers, the formation of an ice cover is highly dynamic; frontal progression is interrupted by sudden collapses which cause the cover to mechanically thicken. The attendant flow restriction can lead to rapid flooding and threats to human safety. Thick, rough ice covers also limit the energy production of hydroelectric generating stations through the winter season. It is important for engineers to understand the processes affecting ice cover formation at freeze-up, and the associated impacts on river hydraulics.
This thesis investigates this topic by way of field monitoring, laboratory experiments, and numerical modeling. A field monitoring program was established on the Dauphin River in central Manitoba, and comprehensive datasets were obtained for three freeze-up periods from 2015-2018. The data and observations constitute one of the most detailed freeze-up monitoring programs to date, and aid in the understanding of the processes of ice cover progression and consolidation. Laboratory experiments were conducted to investigate the effect of freezing air temperatures on the consolidation resistance of a floating rubble ice cover; the link between thermal and dynamic ice processes is not well understood, and is often neglected in numerical models. New formulations were added to the CRISSP2D model to account for effects of thermal strengthening on mechanical thickening of a forming ice cover. The CRISSP2D model was applied to the case study of the Dauphin River to evaluate its ability to simulate ice cover formation and associated water levels, and to highlight potential areas for future model development.
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Keywords
river ice, freeze-up, ice jam, consolidation, hydraulics