In the Upper Vistula Basin, series of check dams are located on almost each of mountain stream. These streams are strongly affected by the presence of dams that disrupt sediment movement in the channel. Moreover, the check dams are in poor technical condition. The current study focuses on Krzczonówka Stream, a left-bank tributary of the Raba River, where restoration works in the form of a lowering of a check dam were undertaken in 2014. The aim of the project was the continuity of the stream corridor for fish migration restoration. This paper aims to provide an analysis of streambed evolution and a numerical analysis of the impact of check dam lowering and removal of sediment previously accumulated upstream on geomorphologic conditions in the studied stream after three years of project execution. A 1D sediment transport model was employed to estimate the areas of erosion and deposition throughout the river course. The calculations show, that the thickness of deposited sediment ranged from 0.20 up to 0.91 m at 1.5 km of the reach. The layer thickness deposited form 2.1 to 1.75 km of the reach, is rather thin; subsequently, the layer thickness increases and the highest values reaches at the area of 1.35 – 1.7 km. The local erosion is observed in 1.1 km of the reach. Very important is that the identified erosional and accumulation tendencies are the same at corresponding cross sections measured as calculated based on the model. This also provides a practical form of model validation. Additionally, the stream channel evolution on the base on low annual water stages in Krzczonów gauging station, located downstream the dam, indicates that the bottom has increased in this section by about 50 cm. The comparison of cross-sectional geometry in years of 2015-2016 (after flood event) shows, that the stream channel moved in the transverse direction (bank erosion and deposition) and the streambed level has changed slightly. Currently, the stream channel seems to be in a state of non-achieving hydrodynamic equilibrium. Thus, further field measurements will try to indicate when this balance is achieved.