Summary:

The river channels exploitation leads directly and indirectly to they river training. The usual consequences of that is a dramatic change of river dynamics. Thus in the studies – especially field studies – which can show the better explanation of river forming channel and river processes are the key elements when one intends to talk about river renaturalization and river rehabilitation. In the following paper the results of investigations of morphological changes within the outlet of sand-gravel river are presented just after the bankfull. Also the granulomerty of the considered river channel material was taken into account. On the base of very detailed field survey done along a mouth unit part of the Raba River situated in front of Polish Carpathians, the authors provided the analysis of morphological and granulometric changes of the river bed and channel. Under the consideration the authors took river bed forms, ricer bed armoring and sub-pavement granulomentry as well as river geometry of the particular cross-sections. Work was done (and is continued) within the years 2005-2006 but only the data from 2005 year are presented here. It was fund that along the research channel many new so called riffle and pool sequences are present as well as it was investigated that new sand-gravel bars height is up to 1.1 m. The granulometric analysis of the material trapped within the new bars shows different granulometric composition along the different vertical levels of the material building up those structures. If there is no armoring level present the 0,0–0,05 m level d50 = 0,007 m. (probe A), whereas if the armoring level is present d50 = 0,013 m (probe B). The local changes in altitude of the river channel bottom are from 0.5 m (in-deepening) or 1 m (up rising). After the bankfull stage – August 2005 – the talweg was shifted around. 50 m, but the meander-like system was still preserved (which dimensions are up to 450 m – the meander diameters and 30-38 m the meanders width). All work was supported within the grant of KBN 2 P06S 075 28.