Summary:

The analysis of variability of riverbed elevation recorded at three selected gauging cross-sections: Raków, Staszów and Połaniec on Czarna River is presented in the current paper. The studies concern the period of more than fifty year. Focus was on the analysis of the riverbed changes in relation with known anthropogenic activities in the bed of the river. In addition, an analysis of grine size distribution of sediment forming the river channel was examined. The studie was done in order to identify the structure of riverbed, as well as the intensity of sediment movement throughout the ricer course. Czarna river is a left tributary of the Vistula river, at a considerable length, is transformed as a result of technical river channel regultion. At 36+000 km of the river course, Chańcza dam was set. The mouth of Czarna river is located close to the Town of Połaniec. The river channel aspire to shape a new longitudinal profile of hydrodynamic balance in new conditions of fluvial system, by changing its shape in the vertical and horizontal direction. As indicated by river channel observations, changes are very fast after a disturbance, after which they are weakening, and the riverbed reaches again hydrodynamic equilibrium (eg. In Połaniec). An important role in riverbed development plays also bank erosion process. Riverbed is supplied with thicker grains than this fraction, which forms the bottom. In the river channels where this process takes place accummulation of sediment in the bottom is observed. According to observations, the variability of sediment characteristic diameter along Czarna river course is disturbed. This is due to the seiment supply by the tributaries of Czarna river and its ability to transport the grains with a maximum diameter. Moreover, these disturbances are observed in the section upstream and downstream of the Chańcza reservoir