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Estimation of Composite Roughness Values During River Ice-Cover Breakup

Author(s): Soheil Ghareh Aghaji Zare; Stephanie Moore; Colin D. Rennie; Ousmane Seidou; Habib Ahmari

Linked Author(s): Colin Rennie

Keywords: River ice; Acoustic techniques; Break-up; Composite roughness

Abstract: For rivers in cold winter climates, a roughness coefficient needs to be calculated for the ice covered condition, which is a combination of top (ice) and bottom (river bed) resistance coefficients. This coefficient is usually called the “composite roughness”. The composite roughness coefficient varies throughout a winter as a complicated function of river ice processes. For example, during river ice break-up the accumulation of fragmented ice can lead to channel blockage in some locations through a process called “ice jam formation”. The composite roughness value is difficult to estimate in such highly unsteady situations, thus field data are usually required. However, direct measurements of ice cover condition and flow stage are extremely difficult and dangerous due to the dynamic and hazardous nature of river systems during most ice stages, and particularly during the unstable break-up period. In this paper we present composite roughness values calculated from a continuous velocity profile time series collected in Nelson River, Canada under ice cover throughout a break-up period using acoustic instruments. Composite roughness then calculated using some well known methods and results compared to field investigations.


Year: 2014

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