The paper presents a method for modelling the erosion phenomenon of riverbeds on sections limited in length of study. The research considered sections of the river on which various constructions are located in the riverbed. The model allows the evaluation of erosion depths on the perimeter of the flow section in various hydrological regimes and geotechnical conditions. The hydraulically-mathematically designed model is based on the equations of motion of a biphasic fluid (water + sediments) in whites with various geometric shapes of the flow section. The simulation model of the erosion-sedimentation phenomenon was solved numerically with the MATLAB program. The simulation of hydrodynamic erosion was performed on a river section with a length of 350 - 450 m, variable width (90 - 280 m), variable slope, water depths of 1.50 - 4.25 m. The flow of the river section was imposed by the study requirements specific to the riverbed constructions. By using the calculation program, the values of the tangential effort at the wall and the speed at the wall, the erosion-sedimentation depths in characteristic points located in longitudinal profile and cross sections of the riverbed were obtained. The results obtained by modeling were compared with data calculated according to the design regulations and with the data collected by research in the study area.