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Formation, propagation, and recession of ice cover introduce a dynamic boundary layer to the top of rivers during northern winters. Ice cover affects water velocity magnitude and distribution, water level and consequently conveyance capacity of the river. In this research, total resistance, i.e., ''composite resistance,'' is studied for a 4 month period including stable ice cover, breakup, and open water stages in Lower Nelson River (LNR), northern Manitoba, Canada. Flow and ice characteristics such as water velocity and depth and ice thickness and condition were measured continuously using acoustic techniques. An Acoustic Doppler Current Profiler (ADCP) and Shallow Water Ice Profiling Sonar (SWIPS) were installed simultaneously on a bottom mount and deployed for this purpose. Total resistance to the flow and boundary roughness are estimated using measured bulk hydraulic parameters. A novel method is developed to calculate composite resistance directly from measured under ice velocity profiles. The results of this method are compared to the measured total resistance and to the calculated composite resistance using formulae available in literature. The new technique is demonstrated to compare favorably to measured total resistance and to outperform previously available methods.1. Appropriate water releases from upstream water reservoirs or dams according to the water demands for hydropower generation, and urban, industrial, and agricultural water consumption. 2. Hydraulic measurement issues due to disturbance of stage-discharge relations caused by complete or partial ice coverage of control reach, and 3. Early mechanical breakup due to rapid water staging in ice-covered channels, which can lead to ice jam formation and release which increases the chance of severe flooding. Key Points: Study of hydraulic resistance of river boundaries during ice cover period Evaluation of available methods for composite roughness calculation Introduction of a new approach for composite roughness estimation PUBLICATIONSAmong the important factors that determine a channel's conveyance capacity, hydraulic resistance of a covered reach is a factor that varies directly according to the condition of the ice cover.

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Three-dimensional turbulent offset jets were investigated using a particle image velocimetry technique. Detailed measurements were performed for offset height ratios of 0, 2 and 4. The presence of backflow influenced the distribution of the mean velocity and Reynolds stresses. A two-point correlation analysis was used to investigate the spatial distribution of large-scale structures within the inner shear layer of the flow domain. The results revealed that large-scale structures dominate the inner layer of the self-similarity region. Proper orthogonal decomposition was performed on the fluctuating velocity field within the symmetry and lateral planes using the snapshot approach. Results from the reconstructed field provided insight into the contributions of the most energetic structures to the turbulence statistics. The energetic structures contributed more to the Reynolds shear stress and streamwise turbulence intensity, while contributing less to the wall-normal turbulence intensity.

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