INFLUENCE OF CHECK DAMS ON BED SEDIMENT IN THE TENCZYŃSKI STREAM

Aim of research The aim of this research was to analyse an influence of check dams on granulometry of bed sediments in their impact area. Necessary data was obtained during field measurements carried out in May 2017. Sediment was collected using the Wolman’s method. Data collected through this method were used to determine granulometric curves, granulometric parameters and shapes of grains forming riverbed sediment in the region of the studied objects. Material and methods Sediment measurements were carried out below and above the check dams through the Wolman’s method. Grain size curves were then plotted, granulometric and sedimentological parameters were calculated. In addition, grain size and shape were determined using the Sneed and Folk methods. Results and conclusions The number of discoid grain pebbles increased below the dam in relation to the level above the dam. In the material collected below the dam there was a smaller number of spindle-shaped grains than in the material collected above the dam. Above the dam there are larger amounts of finer material than below. This may be related to the retention of even small grains of pebbles in the dam reservoir, in which flow velocity is lower than in the riverbed, thus depositing of carried material. On the other hand, in the lower station, due to the increased water flow velocity, small debris is washed away, and in the bottom of the bed only thick fractions are found.