The aim of the paper is to present the studies on the riverbed erosion on the upper course of Raba river, located from km 81.829 to km 77.751, close to the Stróża gauging station located in km 80.600. This part of the river course is com-pletely changed due to the Project concerning the extension of the Zakopianka road located close to the Raba river. The results of simulation of riverbed evolution before and after the Project carried out by two 1D models (RubarBE and Metoda) are analysed and discussed. The results of computation obtained by both models are verified by field observations carried out in 2001 (before the Project), and in 2009 year (after the Project). The trends of erosion and deposition correspond to the field observations for the dates before and after the Project. Another verification is possible to make for the Stróża cross-section, where observations of cross-sectional geometry and water stages have been carried out from 1900 year till now. The statistical model of riverbed erosion developed for Stróża also confirm the trends obtained there by 1D models.
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The analysis of time variability of riverbed elevation recorded at eight cross-sections of the Upper Vistula River is presented in the paper. The variability is analyzed on the base on the observed low annual water stages and the cross-sectional geometry variation observed over decades. Furthermore, the analysis of riverbed changes in the years 2001 - 2011 was done in 16 cross-sections located between the Koło and Zawichost gauging stations. Based on the analyzed changes in the riverbed elevation of the eight tested gauging stations it should be noted that since the beginning of the observation period, that is from about the beginning of the 20th century to the mid 1960's, in the Upper Vistula River riverbed erosion can be observed with a slight tendency for accumulation. As a result of technical regulations of the river channel of the Vistula River from km 247 +000 to 295 +000 carried out in the years 1975 to 1982, intensive processes of riverbed erosion has occured. In most of the 16 profiles it was found that in the years 2001-2011 the river channel was deepened. The occurrence of local riverbed deepening at the river banks was also observed. ...
The analysis of variability of riverbed elevation recorded at five selected gauging cross-sections of Nida River, and at three gauging stations of Czarna Nida is presented in the paper. The studies concern the period of 60 - 80 years of observation. The trends of riverbed changes during the study period at the selected gauging stations were calculated based on the variability of observed minimal annual water stages. The reasons for the observed changes in the river course and channel geometry are given. These changes were caused by river regulation consisted of the shortening and narrowing of the river channel. Moreover, grain size distribution analysis in the selected gauging stations of Nida River and characteristic diameter variability of sediments along the river course examination are presented. These analyses were to evaluate the variability of characteristic diameters along the river course in connection with observed changes in cross-sections' geometry. Additionally, to confirm the process of erosion or deposition recognized in the examined river channels, hydrodynamic equilibrium was determined. Three methods were proposed and used: the mean velocity and critical velocity in the main river channel comparison, the stream power value calculation which defines the character of the river channel, and the WWK ...
