STUDYING THE GRANULAR ROUGHNESS OF RIVER CHANNELS BOTTOM
The main tasks of the dynamics of channel flows, the solution of which depends on the quality of hydraulic calculations and the reliability of channel forecasts in rivers with moving soil of bottom sediments, are the problems of estimating energy losses along the length and determining the flow rate of channel deposits in the natural river channels. In the river flows, these issues are interconnected through the mechanism of interaction between the stream and the deformable riverbed. By nowadays, it has been possible to obtain a large number of calculated recommendations in the field of sediment transport modelling. Considering that a universal solution in river hydraulics has not been established yet, this problem remains relevant. The performed work is devoted to the issues of assessing the hydraulic resistance of the channel and improving the model of sediment transport in rivers using the database of field measurements on rivers. The results obtained during the research have improved the quality of sediment transport modelling. In the event that the purpose of hydraulic calculations is to compute the free surface marks along the length, then on the rivers sections where the large bottom sediments predominate and sediment transport is limited, preference should be given to the calculated dependencies having the structure of A.P. Zegzhd formula. On the rivers with fine-grained soils, it is proposed to use in the calculations the dependencies constructed on the basis of the established relation between the Chezy coefficient and the current velocity. When the purpose of hydraulic calculations is to forecast channel reformation on a river section, it is recommended to use the modified L. van Rijn formula to calculate channel sediment discharge. At the same time, it is recommended to evaluate the granular bottom roughness in the sediment flow formula using the Manning - Strickler and A. P. Zegzhd formulas.