This paper is focused on the genesis and evolution of the Bug river valley near Janów Podlaski (borderland of the Belarus territory). In this area, the connection between geological and morphological situation and non-direct human activity is clearly visible. The section of the valley between Zaczopki and Gnojno has a variable width of the bottom. It changes from 6 to 1.5 km as a result of crossing the marginal zone of Wartanian ice-sheet. In the narrow part of the valley a gap is formed. In the cross-section of the wider bottom of the valley there are two higher terraces and the wide distal and proximal floodplains with many traces of the changing channel pattern from the Vistulian braided river through Late-Glacial large meanders to Holocene small meandering channels. Considering the existing natural conditions, which shape mainly the valley, the human impact is noticeable in the fast change of deposition processes. It is leading to the development of new morphological forms, especially in the channel. These are different types of bars, which are formed in the place where river competence is low. The Bug river has a tendency to braiding again.