Features of the hydrological regime and channel processes on the Iltsya river (Chornyy Cheremosh basin)

Abstract

This publication analyzes the features of the hydrological regime and channel processes of the Iltsya River, based on regular observations and during the expedition trip in June 2019.The schemes of basin distribution and geomorphological zoning of the studied object, curves of connection of water consumption and levels Q = f (H), graphs of the course of maximum, average and minimum water levels, and also cross sections on key sites are presented in the work. Conditions of channel formation of natural watercourses are a complex and multilateral process which is closely connected with natural features of the territory of their basin.The main factors of the natural channel process are the geological structure of the area, sediment flow and grain size. These factors are key, however, the processes of channel formation are also influenced by additional factors that are temporary or local in nature. At the same time, we should not forget about the influence of the anthropogenic factor, the results of which for the basins of small rivers can sometimes even dominate for some time over the main ones mentioned above. All these factors not only affect the channel process, but also difficult to interact with each other. The geological structure, including the lithology of rocks, as well as the relief of the territory, have a direct impact on the shape of the valley, the longitudinal profile, the composition of channel-forming sediments, and hence the stability of the channel. Water runoff is the main active factor that depends on the hydrological regime of the river and determines its water content and size. The nature of the sediments and their regime is a factor that determines the rate and direction of vertical and horizontal deformations of the channel. The object of our study - is the river Iltsya, a small left tributary of the ChornyyCheremosh, which is characterized by specific geological conditions, and therefore significantly different from other small rivers in the region, including neighboring tributaries of the main river (ChornyyCheremosh). The second feature of the studied river is that the lower part of its basin is located within the Vorokhta-Putilsky ancient terraced lowlands, while the sources are formed within the Pokutsko-Bukovynian Carpathians, which in turn determines a certain specificity in the formation of its channel. This geological and geomorphological feature of the Iltsya river basin distinguishes it among numerous similar small rivers of this region of the Ukrainian Carpathians. Summarizing all the above, we have made some conclusions, the basin of the river Iltsya is currently little studied, both in terms of hydrological regime, channel processes and geomorphological studies, although in fact it is quite interesting and not typical of project, which raises many questions that require more detailed study. The presence of a long series of observations, allows us to identify general tendencies to the gradual incision of the channel in the area of the hydropost, although with little intensity. Visual inspection showed more manifestations of horizontal transformations associated with the movement of alluvial ridges and erosion of the shores. The greatest feature of the Iltsya river basin is the polymorphic formation of its channel system, because within the Vorokhta-Putil lowlands the river Iltsya and VelykyiRosysh occupy a wide valley of the ancient pliocene river, and this nuance has the greatest influence on the nature of riverbeds within its limits.