Key changes across valley floors in mountain areas affected by different levels of human impact: a case study of the Ochotnica river catchment in the Polish Carpathians

Abstract The goal of this paper was to present knowledge on changes in the morphodynamic structure of the Ochotnica River (Polish Carpathians) and transformations within its active river zone since the end of the 19th century. The study used a set of archival and contemporary cartographic materials and the results of three-fold field mapping of the morphodynamic structure of the riverbed. Direct and indirect human interference with the natural environment of the catchment and the fluvial system was taken into account in the analysis. Analysis of changes in the morphodynamic structure of the Ochotnica and its active river zone since the end of the 19th century indicated significant changes in the development trend of the riverbed. The contemporary structure of the Ochotnica is more complex than in the 1980s. There has been a fragmentation of the riverbed into sections with different morphodynamic sections. The proportion of erosive sections has increased, which explains the reduced in the width of the active river zone of the Ochotnica. The average width of the active river zone of the river between 1861 and 2022 has changed from 80 m to 18 m. Human impact has been identified as the main reason for the changes in the morphodynamic structure of the riverbed and its active river zone. Currently, only the unregulated sect ion is characterised by free lateral migration of the riverbed and the widest active river zone (∼ 28 m).