Determination of Parameters in the Formula for Sediment Transport Capacity in Low Sediment-laden Flows and Its Application in the Lower Yellow River

The determination of parameters in the formula for sediment transport capacity will exert a significant effect on sediment transport processes.The formulae for sediment transport capacity mainly consider hyperconcentrated flows,which are currently applied in numerical simulation of sediment transport and channel evolution processes in the Yellow River.However,low concentrated floods occur frequently in the Lower Yellow River (LYR) after the operation of the Xiaolangdi Reservoir,and the applicability of these formulae is limited because the parameters are originally obtained based on hyperconcentrated flows before the reservoir operation.In this study,the hydrological data in the relative equilibrium state were collected from the hydrometric stations.Furthermore the calculation relations are determined between the parameters in the formula and the comprehensive parameter,which were then applied in the numerical modelling of the 2017 flood in the LYR.The results show that:(1) the coefficient and exponent of the formula proposed by H.W.Zhang show a negative power functional relationship with the comprehensive parameter,and reach constant values lastly;(2) comparisons are made among the simulated sediment concentration hydrographs calculated by three methods.The simulated hydrographs are in best agreement with the observations in the braided reach when the formula proposed in the study is adopted,with MAEs reducing by 50% and 67% at the stations of Jiahetan and Gaocun respectively.The formula established in the study can reflect the effects of flow and sediment dynamics,which can improve the accuracy of the one-dimensional morphodynamic model.