Author(s): Yasuhiro Yoshikawa; Yasutaka Kuroda; Takaaki Abe; Toshihito Toyabe; Hotaek Park; Kazuhiro Oshima
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Abstract: The objective of this study is to clarify the relationship between the formation of ice jams and the cross-sectional profile of ice-covered rivers. We performed hydraulic experiments in a test channel to replicate an ice-covered river. The test channel had four sections, each of which had a different width and bed slope. Hydraulic conditions such as area and discharge of the ice pieces and flow discharge were varied, photographs of the resulting ice formations enabled the measurement of the ice-piece-assembly thickness and the velocity of the assembling ice pieces using particle-tracking velocimetry. The results indicate that ice pieces tend to stagnate in areas of greater water depth and lower water-flow velocity and that ice jams form under the conditions of large ice-piece size, high ice-piece discharge, and low water-flow discharge. Moreover, the results allow us to deduce the relationship between ice-piece transportation and water slope. The ice-jam probability is estimated from the ice-jam scale, , which is a function of the densimetric Froude number of the ice-piece assembly (itself based on the ice-piece assembly thickness and velocity) and the reduction ratio of the river width at the ice-jam location. Furthermore, ice jams tend to occur at locations where both the densimetric Froude number of the ice-piece assembly and the river-width-reduction ratio is small.
Year: 2016