engleski

The Meander Cut Off Morphological Evolution

In the river engineering aspect, cut-offs pertain in river regulation actions that have significant effect on morphodynamical changes of the river channel. Shortening of the river course increases energy slope, which imply increase of shear stress on the river bed and disturbance of the river channel stability. To enable timely reaction in case of adverse effects, it is necessary to monitor the new situation. Due to diversity of geological, hydrological, hydraulical and morphological conditions, each river reach is a unique section. This paper gives theoretical aspects of the river channel evolution in the cut-off after creating the weir on the main channel of the river. Also, a meander cut-off results of morfologic changes observations are presented. Development of the river geometry has been observed for the period of one year, as well as the changes of the hydrodynamical parameters. Methodology of data evaluation is demonstrated where focus is been on distinction beetwen total eroded material and material which was caved in cut off from river banks. Also, analyzes of the influence of the river discharge and water surface level slope on erosion progress in the cut-off within a year. Volume of the total eroded material is approximated by the exponential curve. Prediction of cut-off evolution time is based on assumption that cut-off would be hydro-morfological stable when average cross section areas became equal for cut-off and for adjacent river bed. Predicted cutt-off evolution time is from min. 3, 5 to max. 8 years.

river cut-off; morphodynamics; evolution time; drift erosion; river bank erosion.

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