Evaluation of riverbed process parameters under conditions of a changing hydraulic regime

Introduction. The authors address the development of river bed deformations under the influence of a water flow in conditions of a changing hydraulic regime and scroll-bar riverbed processes. The relevance of the publication is explained by the unavailability of reliable waterbed shape forecasting methods needed to ensure their normal ecological condition. Meanwhile, the analysis of the motion of solid particles is associated with the sediment flow rate at the level of saltation, and with hydraulic friction losses at the level of microforms. New dependences are proposed for the sizes of bedforms, depending on the parameters of a streamflow. Materials and methods. The influence of factors in the form of new dependencies has been proven on the basis of the study of recent and classical research works, an experimental study of the formation and development of the bottom relief in case of a change in the hydraulic regime of the streamflow. Results. The author has studied the reasons and conditions for the formation and development of bedforms at the initial stage of interaction between the flow and the riverbed, as well as the factors influencing the formation of the bottom relief which is initially smooth. Structural levels of the waterbed evolution process have been analyzed. The experimental data were analyzed to identify a universal correlation between the flow parameters and the height of the developing bottom microrelief elements, from which the resistance formula is derived that coincides with the Knoroz dependence for steepness of bedforms that complies with the Boussinesq dependence. Conclusions. The results of this study can be used to prognosticate the riverbed evolution process in case of changing hydraulic regimes of water flows in the waterbed, composed of erodible soil not only at the initial stage of formation of bedforms, but also in the course of the bottom relief development.