Along the paper, we described research on chosen hydrodynamic parameters in near woody debris and downstream and upstream of obstruction river bars, which were formed within the area of the debris. Values of velocities measured in the field served to calculate shear stresses and other hydrodynamic parameters, which are characteristic for the process of the river bars formation. The study was carried out in the Raba River in the South Poland. The results show that the woody debris present on the river bed strongly influenced process of the formation of two channel bars and change the hydrodynamic parameters within the research reach.

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