EFFECTS OF SNOW JAMS ON FLUVIAL ACTIVITIES IN THE HIGH ARCTIC

During break-up in the High Arctic, ice jams are insignificant, but large quantities of snow accumulated in the valleys strongly affect fluvial processes. Near Resolute, Cornwallis Island, many channels were first formed in valley snow drifts and their positions were unstable. Channels carved in the snow can easily accommodate changing discharge by a modification of their width, depth, and velocity. This causes considerable variation in the at-a-station hydraulic geometry relationships. The availability of sediment is locally restricted by the snow lining along the channels, although some fluvial sediments deposited on the snow revealed that peak flows could entrain very large boulders. Several depositional features observed in the study area also indicated that fluvial activities can extend over a broad zone beyond the confines of the summer channels. This study suggests that, by increasing discharge, snow jams enhance the erosional power of streams, but by interposing between streamflow and the valley floor, the snow can limit the supply of sediments. Whether the erosional or the protectional tendency dominates will depend upon the snow jam characteristics along various segments of the High Arctic streams.