. According to field observations, currently in the Republic there is an active destruction of the bedrock costs and slopes of more than 80 % of water bodies. The total length of the coasts of reservoirs that are subjected to processing is about 350 km with a maximum regression of more than 40 m. The reasons of activation of process of processing of the coast caused by construction of new reservoirs of power engineering purpose are considered. The length of the coasts of the new reservoirs exposed to abrasion processing will increase in the near future by more than 30 km, which will have some impact on the surrounding areas and objects of the regional economy. As for the channel-type reservoirs, processing of the cost is being expanded only in the near-dam part of the reservoir and reaches 40 % of the coastline. At the same time, the value of this indicator might be up to 70 % of the length of the coasts of the lake-type reservoirs. Having taken this problem into account, it became necessary to generalize the corresponding accumulated factual data and the results of scientific research. Therefore, the results of theoretical studies of the process of processing of coastal slopes of reservoirs of hydroelectric power plants of Belarus presented by the author, along with the updated data, are of practical importance for decision-making in the regulation of engineering activities for coastal protection. The article presents the theoretical issues of the development of abrasion processes in the banks of reservoirs of hydroelectric power plants in Belarus, based on the data of field observations and laboratory studies. On the basis of the law of conservation of mass and taking into account hydrological features of reservoirs, geological structure of relief and granulometric composition of soils forming the bank, balance mathematical models of development of the equilibrium coastline and the profile of the dynamic equilibrium of the banks that are subjected to processing are developed, criteria for the stability of slopes have been obtained.