Anthropogenic conditions of change in the structure of the channel of a mountain river on the example of the Ochotnica River (Western Polish Carpathians)

Human economic activities in the catchment directly or indirectly affect the formation and contemporary functioning of river channels. Mainly through changes in land cover in the catchment, hydrotechnical works carried out in river channels, and the increase in development in the valley floor, human influences the circulation of water and sediment within the slopes and fluvial systems. This is usually reflected in the variation of the morphodynamic structure of river channels. The research was carried out in the riverbed of the Ochotnica River (Western Polish Carpathians), which is a left tributary of the Dunajec River. To understand the contemporary structure of the riverbed, a geomorphological mapping of the riverbed and an inventory of hydrotechnical buildings were carried out in 2021. Erosion and accumulation forms were characterized, and the maximum diameter of the channel material was determined. The minimum and maximum water levels for the period 1984-2021 were also analyzed. The morphodynamic structure of the Ochotnica riverbed was compared with the results of the mapping, which was carried out in 1984 and 2001. An increase in the number of erosional forms and a decrease in the number of accumulation forms along the longitudinal profile of the riverbed were found. An analysis of changes in the land cover of the catchment based on archival and contemporary cartographic materials was also carried out. In the period 1930-2019, an increase in the proportion of forest area, and a decrease in the area of arable land and grassland was found. Also noticeable is an increase in the area occupied by buildings at the bottom of the main valley, and in the valleys of tributaries, increasing the share of a sealed area in the catchment. The results of the study documented the impact of land cover changes and hydrotechnical regulations on the diversification of the morphodynamic structure of the Ochotnica River channel, including the intensification of erosion processes.

The research has been supported by a grant from the Faculty of Geography and Geology under the Strategic Programme Excellence Initiative at Jagiellonian University.