The paper presents the results of studies of the conditions of sediment transport of Styr basin rivers, tributaries of the right bank of Pripyat, which were held on 9 rivers of the basin and 2 streams of the Styr River (Stara Styr and Prostyr). According to 30 representative cross-sections of the studied rivers, the hydraulic parameters of channels are measured and channel alluvium is sampled to determine its coarseness. The average flow rates under the bankfull stage are set for the mentioned areas and non-eroding and eroding velocities of the stream flow are calculated. It is determined that the passage of bankfull stages in edges complies with the conditions of dynamic equilibrium of the erosion-accumulative processes. The ratios of average flow velocities under the bankfull stage with non-eroding and eroding velocities enable determining the orientation of channel deformations in the areas of the rivers. A new approach to the determination of non-eroding velocities for unexplored areas of the rivers is represented, which is based on the dependence of non-eroding and average flow velocities at the bankfull stage. It is shown that an increase in slopes and velocities of the stream of the Styr River cause the activation of channel processes down the river.