An experimental study into the bedform morphology in partially ice-covered channels.

Abstract

The advent of winter in cold climates often leads to the formation of border ice along riverbanks, a phenomenon that can persist over substantial portions of the winter, thereby influencing the dynamics and geomorphological structure of river channels. Bed morphology and dunes play a crucial role in sediment transport and influencing flow resistance. Consequently, accurately predicting dune dimensions is important for anticipating the behavior of rivers. Despite extensive studies on bedforms within open channel flows, research on partially ice-covered and fully ice-covered flows remains limited. This investigation, conducted in a rectangular flume at the University of Manitoba's Hydraulics Research & Testing Facility in Canada, delved into how border ice affects bed morphology and bedform features. For each experimental condition, including open channel, symmetric and asymmetric border ice, and fully ice-covered flows, bedform dimensions were assessed against theoretical equations found in the literature. This analysis confirmed the suitability of these equations for describing bedform characteristics in partially ice-covered rivers. Furthermore, the impact of border ice extent, variations in flow strengths, and asymmetry of border ice on bedform features were also investigated. The occurrence of bedforms within the channel width was notably influenced by the presence, positioning, and varying extents of partial ice cover. The influence of ice coverage on the distribution of bed feature formation was markedly pronounced at lower flow strengths, whereas it became minimal at higher flow strengths.