Author(s): Karl-Erich Lindenschmidt; Apurba Das; Joel Trudell; Keanne Russell
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Keywords: River Ice; Ice Related Flooding and Flood Mitigation
Abstract: Flood hazard and risk analyses and mapping were carried out to assess two options to mitigate ice-jam flooding at the town of Fort McMurray, which lies at the confluence of the Athabasca and Clearwater rivers and is prone to ice jamming and subsequent flooding. The recent extreme ice-jam event of spring 2020 was included in the stage frequency analysis, which is vital for the flood hazard and risk analyses. Vital flow information was missing due to damages to the Athabasca River gauge from the ice jamming. However, using the objective function of highwater mark elevations, a river ice model was calibrated to yield a flow of 2,700 m3/s along the upper Athabasca River stretch at the height of the event. A second objective function, the extent of the ice jam, yielded a volume of ice of 30.1 million m3 that accumulated in the jam. To refine the calibration of the ice-jam morphology, a third objective function, the extent of flooding throughout the town of Fort McMurray, was used. A Pareto optimum of the three objective functions yielded maximum backwater level elevations of 248.686 m a.s.l. at the Clearwater River mouth and 248.231 m a.s.l. at the Athabasca River gauge at the peak of the flooding. The backwater level profile along the Athabasca River due to the ice-jam event lies within the realm of return periods 1:80 and 1:100 annual exceedance probabilities (AEP).
Year: 2022