Improved formula of sediment transport capacity and its application in the lower Yellow River

The calculation of sediment transport capacity is of great importance in modelling of morphodynamic processes in alluvial rivers. Recently, worldwide fluvial sediment load is reducing especially in the Lower Yellow River (LYR), while the commonly used formulas of sediment transport capacity are specially developed for relatively high sediment-laden flow, which needs some improvement for the varying flow and sediment regime. The measurements during a long period (1956-2020) covering 4974 datasets in a quasi-equilibrium state were collected at seven hydrometric stations of the LYR, and the hydrodynamic variables related to suspended bedmaterial load were classified, in order to determine the critical parameters (K and M) in the widely used formula proposed by H.W. Zhang. The calculation relations were firstly developed between K and M and the comprehensive flow-sediment factor (STP), under various combinations of flow and sediment, which reduce the uncertainty related to modifying model input parameters. The improved formula was further applied to simulate the morphodynamic processes in the LYR. Results indicated that the improved formula presented the best accuracy in the simulation of morphodynamic processes induced by low or high incoming sediment amount, compared with the other two formulas. This improved formula can be directly applicable to the varying flowsediment regime and achieves the accurate simulation of the hydrograph of low sediment concentration in the LYR.