Extreme hydro-meteorological event disrupt the balance of natural systems, such as river channels. This paper focuses on changes in mountain valleys associated with a hydro-meteorological event that occurred in the Polish Carpathian Mountain in May and June of 2010. On three rivers (Ropa river, Bielanka and Bystrzanka streams) the geomorphological effects were mapped. Continuous and high intensity rainfalls, the sum total of which exceeded 432 mm in May and June, contributed to the significant increase in water levels and changes in the channel morphology. The dominating process in the upper courses of the streams was erosion while in the middle and lower courses it was erosion with deposition, which led to the building of extensive accumulation forms with woody debris. The calculated high values of the unit stream power indicate that Carpathian streams have tendencies to transform the bedrock channel, which is evidenced by the sizes of the transported boulders. The research confirm the hypothesis that grouping of several events in a short period of time is the most important factor shaping river channels in mountain regions.

182 pages : color illustrations ; 24 cm

Water flow in the Polish Carpathians was exemplified by long-term (1988‑2017) analysis of two foothill catchments (of the Skawinka and Stobnica) and two catchments in the Beskidy Mountains (of the Soła and Osława). The work allowed for the determination of the duration of low flows and outflow deficits in relation to changes in thermal and precipitation conditions, as well as land use and land cover. In the selected catchments, the 30-year period brought a decrease in the area of arable land and an increase in the area of grassland and forest. In addition built-up areas increased by 495% between 1990 and 2018. A greater susceptibility to the occurrence of total drought was noted for the Beskidy Mountains catchments, in which the duration of low flows and outflow deficit was greater than in the foothill catchments. At the same time, the mountain catchments proved less susceptible to the emergence of deep drought, on account of their higher levels of forest cover and levels of soil permeability. In regional terms, the durations of low flows and outflow deficits were greater in the catchments located in the eastern part of the Carpathians (those of the Stobnica and Osława), in line with this area’s intensified features of a continental climate.

This study presents the characteristics of the current course of the phenomenon of droughts and floods in the catchment area of a man-made mountainous reservoir and forecasts of water inflow changes to the reservoir over the next three decades. The catchment area of the Klimkówka reservoir on the Ropa River, a tributary of the Wisłoka River, located within the Polish Carpathians was selected for the study. The analysis carried out, using Soil and Water Assessment Tool (SWAT) modelling among other techniques, showed an increase in the importance of low-flow outflow from the upper Ropa catchment and a negative balance of inflow to the reservoir (Q < 2 m^{3 s−1}), manifested by a prolonged duration of low flows and an increase in outflow deficit during the year. The duration of flood flows and the runoff excess during these periods show a constant or decreasing tendency, while the length and excess of runoff increase during large floods. Thus, in the upper Ropa catchment, an increase in the intensity of extreme hydrological phenomena is observed. The prepared forecasts indicate an increase in annual runoff from the catchment in the decades 2021–2030 and 2031–2040 and a marked decrease in the decade 2041–2050. In the annual cycle, the projected changes in the coming decades will take different directions. In December only, throughout the entire period 2021–2050, the outflow will increase, whereas in May it will systematically decrease.