Summary:

Stage correction is currently the most frequently used type of the Carpathian streams training. It aims at decreasing the channel slope and limiting the bottom erosion, which over the last years led to a considerable channel deepening. The aim of the paper is the analysis of the stage correction effect on changes of the channel development and its functioning against its evolution during an over a hundred-year period. The investigations were conducted in the lower section of the Mszanka channel, a right tributary of the Raba River, which was wholly trained by means of stage correction. The training was conducted in three parts in the years 1977-2013. Available archival cartographic and photographic records, results of geomorphological research, etc. were used for the analysis. Information about the present functioning of the channel was obtained from geomorphological mappings conducted in 2004 and 2015. In result of training works, formerly braided Mszanka channel became transformed into a single thread and sinuous channel. 25 concrete drop structures and many steps were constructed in the bottom. The riverbanks were reinforced. In result of stage correction application the bedload was caught between the drop structures, whereas the channel below was underloaded with material. Therefore it became deepened. At this point the next stage of training was started and finally the drop structures were constructed until the river mouth. However, it did not stop the erosion process, although slowed it down greatly. At present the riverbed at this point is incised to the bedrock. Downcutting and lateral erosion play the main role in its development. The channel is unstable and the hydraulic structures are being destroyed, particularly during floods. The greatest error of the training was too big shortening , straightening and narrowing of the channel at simultaneous cutting it off from the material supply source.