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In Russian climate, population and economy security is often limited by dangerous ice phenomena. It is not just ice jam floods, but also about the processes that lead to violation of operating conditions of various facilities (water intakes, roads, bridges) and damage hydraulic structures and fleet. Currently, the rivers’ ice regime characteristics change under the influence of both natural (primarily climatic) and anthropogenic factors. Changes of these characteristics have been analyzed in detail on the basis of observations of 300 hydrological stations for the period from 1936 to 2013. Change of ice phenomena hazard is estimated. During high spring water on the rivers of the North of European part of Russia severe ice jams are regular occurrence. The probability of the dangerous high water which is followed by flooding of settlements, for example for middle reaches of Northern Dvina averages about 35%. Our investigations showed that climatic changes of the last decades led to noticeable changes of the water and ice regime of the rivers. Now we often observe the long periods of freezing up which are followed by formation of sludge ice jam and coming to significantly later freeze-up at high water levels. Break-up during the winter period are now frequent. The last catastrophic flood in this area was observed in the spring of 2013. For an assessment of danger of the hydrological phenomena in the period of high waters and formation of ice jams on the northern rivers of Russia the questions connected with an assessment of probability of such events, calculation of duration and depth of flooding at various water levels with an assessment of the corresponding economic damage are considered. Modeling of formation of maximum water levels and flooding of the territory in the period of a high water and formation of ice jams was carried out by means of the russian program complex “Flood” on the basis of the numerical solution of the two-dimensional Saint-Venant equations. For creation of hydrodynamic model as an example the reach of channel and valley of Northern Dvina river with a total extent about 90 km is considered. The main materials for calibration and verification of model were the data of field researches, measurements of depths; measured discharges of water, morphometric characteristics of the river valley, data of regime observations for the long-term period from 1966 to 2012; satellite data during period of high water and low flow. Results of the carried-out model calculations became the basis for recommendations and proposals on hydrotechnical protection of this territory.