A Systematic Evaluation of Initiation Criteria for River Ice Breakup Using Field Data

• Author / Creator

  Ye, Yanqi

• River ice breakup has great implications to the environment, ecology and economy. A mechanical breakup tends to occur if fast-rising river flow instigates ice movements. The breaking front, the interface between moving and stationary ice, can sometimes travel hundreds of kilometres, resulting in extensive ice runs. A breaking front may also stop, resulting in formation of ice jams and the associated flood risk is high. There are still many unknowns about the mechanism of the onset, sustaining, and stop of ice cover breakup. The hydraulic storage released from the broken ice is postulated to lead to the formation of a non-attenuating, i.e. self-sustaining wave (SSW), offering an explanation to the long distance ice breaking, but the postulation is mainly based on numerical studies in hypothetical rectangular channels. This study focused on the mechanical breakup process of the river ice, serving to improve the breakup forecasting capability. Six empirical and semi-empirical/physics-based breakup criteria were incorporated into the University of Alberta’s River1D model and systemically and quantitatively evaluated using three years of breakup data collected on the Athabasca River and the Peace River. The existence and characteristics of the self-sustaining wave (SSW) under natural channel conditions were also explored.
  This study showed that the empirical breakup criteria based on water level or discharge can often be calibrated to reproduce the documented breaking front propagation. However, the calibrated parameters appeared to be site and situation specific. On the other hand, the physics-based boundary constraint criterion, which is based on the requirement of broken ice sheet to move around geometric constraints in the river, showed better potential to be transferable from year to year and river to river. It did not provide as good agreement to field observations as compared to some of the empirical criteria, emphasizing the importance of adequately accounting for the real channel morphological characteristics when implementing such criterion. The other physics-based criteria based on side resistance and flexural strength of the ice cover did not work well for any of the modeled events. The side resistance is highly dynamic in field condition and hard to quantify. The flexural and buckling criterion reduces to water surface slope criterion is too simplified to use when breakup is initiated by an ice jam release wave. Unlike previous findings about SSW in idealized channel conditions, this study showed that the SSWs in natural channels do not always develop a sharp wave front and long, flat crest under the natural channel conditions. The ice breaking distance and speed, which are affected by the varying resistance along a river, can greatly impact the characteristics of an SSW.

• Subjects / Keywords

  • River ice engineering

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-vhvh-qd97

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.