Author(s): Soheil Gharehaghaji Zare; Stephanie A. Moore; Colin D. Rennie; Joe Groeneveld; Rajib Ahsan; Habib Ahmari
Linked Author(s): Colin Rennie
Keywords: River ice; Numerical modeling; Acoustic techniques
Abstract: This paper uses both numerical modeling and field measurements to describe river ice processes. River ice regime plays a significant role in river hydraulics and morphology in higher latitudes of the northern hemisphere, with important implications for hydro-electrical power generation operations. An ice-cover changes various river characteristics, including water stage and velocity distribution. These variations can influence sediment transport and channel morphodynamics, particularly during extreme conditions when ice-jamming and break-up can locally accelerate the flow, and ice can mechanically scour the river bed and banks. Although the influence of ice on rivers is tremendous and clear, it is not well studied largely due to the difficulty and danger of river ice field studies, especially during the unstable break-up period. In this paper we studied river ice conditions in the Lower Nelson River, Northern Manitoba, Canada, during winter 2012 using both numerical modeling and In-situ autonomous field measurements to validate the model predictions. The accuracy of numerical models is an intrinsic concern, especially in the analysis of dynamic processes such as river ice, and verification with field data is essential. . The ICESIM was originally developed by Acres International Limited (now Hatch) in 1973 for studies of the Nelson River hydroelectric plants; since then it has been continuously improved. The field data were collected from a bottom mounted instrument pod deployed below the ice-cover for a four-month period (March-June 2012), which included both the stable cover and break-up periods. Instrumentation included a 546 kHz ASL Multi-Functional Acoustic Water Column Profiler (MF-AWCP) and 1200kHz TELEDYN RD Instrument Acoustic Doppler Current Profiler for measurements of water velocity. The MF-AWCP could measure frazil ice particles in the water column and more importantly, the variation in the condition and thickness of the ice cover. In this paper we demonstrate the model capability by comparing measured and model-calculated results, focusing specifically on the model's ability to predict ice thickness and timing of ice-cover stages i. e. freeze-up, stable ice-cover, and breakup.