Simulation of ice and sediment processes in an alluvial stream

The flow regime of streams in the northern hemisphere can be largely affected by ice formation during the winter period. The ice cover can affect not only the river hydraulics of a particular reach but can also influence important sedimentation processes. Although the effects that an ice cover may have on flow hydraulics are reasonably well understood, our understanding of its impact on sedimentation processes is much less developed. The sparse availability of continuous and comprehensive information on fluvial behavior during the winter period has contributed to this lack of understanding. Numerical models are one means by which to bridge this knowledge gap and improve our understanding of the complex interaction between ice covers, river hydraulics and sediment transport. Several ice simulation models have been developed and applied over the years. Of these, ICESIM has been widely (and successfully) applied in studies of several hydroelectric projects across Canada. The robust algorithms of the model have been successfully calibrated and utilized to simulate the river hydraulic characteristics and ice cover formation. The ICESIM model was originally developed by Acres International Limited (now Hatch) in 1973 for studies of the Nelson River hydroelectric plants and since then it has been continuously advanced and improved. In a recent series of improvements, the model was converted (from Fortran) to run on a Matlab platform, and a sediment transport simulation module was also added. The resulting model, ICESIMAT, is a onedimensional, steady-state model capable of the simulation of ice cover formation and sediment transport in a river. In a recent study, ICESIMAT was applied to simulate ice cover formation and sediment transport on the Lower Nelson River in northern Manitoba, Canada. The results of the numerical simulations were validated by in-situ measurements performed during several field campaigns at the study site. This paper summarizes the model capabilities and the results of these investigations.