Abstract

For a substantial portion of the year many Canadian rivers are frozen. River ice is known to have an important impact on the water cycle and hydraulic engineering infrastructures. From the hydraulics perspective, the formation of an ice cover on the river surface causes an increase in resistance to flow and therefore a decrease in discharge to downstream. In the subject area of ice covered river hydraulics, there have been limited studies. In this study we have quantified the differences in flow velocity, discharge and flow energy distributions between conditions with and without the ice cover. We have also estimated the roughness of the ice cover underside using the boundary layer theory. Based on our flow analysis of a larger number of ice-covered rivers in Canada, the boundary layer profiles beneath the ice cover and above the channel bed are rarely symmetric, i.e. the dynamic effect of the ice cover and that of the channel bed differ. Many of the observed velocity profiles are too complicated to be described using simple analytical functions. The presence of the ice cover can reduce the hydraulic radius of a cross section by as much as 46% and flow discharge by 60%, in comparisons to the corresponding values associated with open channel conditions. Under ice covered conditions the flow is very sensitive to the friction parameter. For a given river cross section, the difference in flow velocities with and without an ice cover is between 39% and 60%