This paper shows variability of fluvial transport of the Wieprz river. The catchment of the upper Wieprz river to profile at Guciów located in Central Roztocze Region. In Wieprz during the hydrological years 1996–2006 average annual flow is 1.32 m3⋅s–1, which correspond to the outflow – 41.5 Mm3⋅a–1. Extreme values of the flows varied from 0.5 m3⋅s–1 to 13,1 m3⋅s–1. Outflow the Wieprz river has feature for the snow-rainy hydrological regime. During the study the annual average suspended load amounted 737 Mg. The annual average dissolved load amounted 10 343 Mg. The bed load estimated of the dissolved load and 1% of the suspended load. The monthly average suspended load and dissolved load were least in the November and were highest in the April. During the period of researches, the average mechanical denudation rates 2.4 Mg⋅km–2⋅a–1. Chemical denudation rates were much higher –36.1 Mg⋅km–2⋅a–1. Their differentiation are similar in other regions of Poland.
The long-term evolution of the river beds of Nida River in Pińczów and Wiślica gauging station as well as an analysis of the causes of significant cases of lowering of the bottom of stream beds are presented in the paper. The intensity of river bed evolution as a stochastic process is described with the use of a statistical model. The analysis of the intensity of the process of river bed erosion was conducted under the assumption that the observed long-term trend of the lowest annual water levels reflect the elevation of the river bottom in the same years. The recorded observations at the Pińczów and Wiślica gauging stations on the Nida River, covering over 70-year period of time, are analyzed. Observations of the variability in the studied bottom levels over the decades allow concluding that the great transformation of riverbeds occurred there. The observations and calculations show that in Pińczów multistream or meandering river bed changed into straight channel and the process of shallowing of the river bed appeared. At the Wiślica gauging station the process of riverbed erosion with the variable intensity was observed. The research shows that the causes of these changes observed in Pińczów and Wiślica are not natural, but rather of human activity.