The paper presents the influence of block ramp on system and morphological riverbed. One of twentyfive block ramp structures, located in the Porębianka River and situated in the central part of the cascade, was chosen for testing. In the observed section of the river, high morphological variability of the riverbed was observed in the years 2010–2011, caused by freshets. Additionally, in one period, the morphological changes were also caused by river training work, consisting in repairing block ramps of increased roughness, which were destroyed during the freshets, as well as damaging involvement with the riverbed. Despite the anthropogenic impact on the river channel, the research has shown that the morphology of the riverbed is returning to its natural structures, which are characteristic of the braided rivers. This confirms the thesis that the block ramps of increased roughness cause differentiation in river morphology, and restoration of the braided character of the channel. Therefore, we can conclude that river defends itself against damaging human activity. In addition, the paper describes the beginning of the movement of the debris, for the grain of boulder located in the Porębianka River, in the hydrodynamic conditions persisting during field measurement series. These conditions were based on Shields’ diagram and the graph showing the relationship of threshold shear stress for the given grain diameter of boulders.
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