Dec 21, 2014

Impacts of the freshet on ice cover breakup and resulting flood risk implications along the Upper Qu’Appelle River SK, Canada

During the ice breakup period in the Upper Qu’Appelle River (QAR), higher flows from the freshet can lead to ice jamming, overtopping of channel dykes and bridge decks and flooding of surrounding agricultural areas along the river The Qu’Appelle River dam regulates the flow from the Lake Diefenbaker to the downstream upper Qu’Appelle River (Figure-1). At the end of the winter season, ice thicknesses begin to reduce due to increased air temperatures and river water temperatures. Despite of drastic reductions in discharge prior to freshet runoff, mechanical ice breakup and jamming may still occur, depending on the amount of snow remaining in the basin, the strength competency of the ice cover and the rate at which air temperatures increase. Previous studies provide an indication of the severity of ice jamming and flooding that could occur at the most vulnerable section of the Upper Qu’Appelle River, between the PFRA Bridge and Tugaske Bridge bridges (Figure-3), where dyke crests and bridge decks are lowest in elevation relative to the channel.
Figure 1: The Qu'Appelle River