Building a predictive model of ice jam occurrence on the branched site of the Tom River

The questions of the influence of geomorphological and anthropogenic factors on the hydraulic structure of the flow, modeling of the processes of opening and ice jam formation in the area of the Tom River floodplain with many branches, taking into account the characteristics of the ice cover. The article presents a generalization of the previous results on the effect of geomorphological factors on the hydraulic flow structure, the study of the formation and destruction of the ice jam phenomena in relation to the object of study - the floodplain area with many arms of the Tom River, and the presentation of the process of the conducted modeling and analysis of its results. The studied area is unique, several geomorphological factors combine here, such as the water surface slope and channel capacity, with a consequent impact on the process of ice jam opening and formation. The influence of anthropogenic factors on aggravating or mitigating the existing geomorphological structure is also considered. An analysis is made of the process of opening of the river for different initial conditions: for larger and smaller water flow in the system, as well as for the presence or absence of ice jams at the entrance to the system. The essence of the problem is the redistribution of water in the flow in the presence of ice jams at the entrance to the system. With an ice jam, the pattern of distribution of parts with ice jam opening and formation is substantially different than without it. The study materials include: bed elevation model taking into account recent developments due to the human impact, measured water consumption, ice thickness and snow depth on the ice taken for many years. The tool, giving an integrated characterization of materials used in the study, program HEC-RAS 4.1.0 was used for modeling. One of the tasks of modeling was the definition of areas of possible ice jams at different flow rates of water at the opening of the river. To determine the possible locations of ice jams, the dimensionless coefficient of the opening of the river was identified and calculated. It was based on the ratio of factors aimed at the destruction of the ice cover and the factors that directly or indirectly impede this. Thus, the denominator was the kinetic energy per unit of mass flow, and the numerator was the product of the resistance of ice by compression, the open area beneath the ice and the ice thickness. A significant impact of redistribution of water content on the process of ice jam opening and forming is considered. Illustrations of the research area, examples of the graphs and maps as well as a table with the balances of water flow in the case of redistribution of water content on the site are given. The results of the analysis of the produced model are provided, an analytical interpretation of maps of the opening coefficient is offered, the results of modeling and of field observations are compared.

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