Sediment transport capacity of low sediment-laden flows

Many large rivers are experiencing a significant reduction in sediment flux owing to human activity. Sediment transport capacity directly affects the predictive accuracy of sediment concentration in morphodynamic modelling. A total of 1092 datasets with extremely low sediment concentrations in a quasi-equilibrium state were selected at five hydrometric stations of the Middle Yangtze River, and used to determine two parameters of a sediment transport capacity formula proposed by Zhang Ruijin. Firstly, the relationship between the effective sediment transport capacity and the comprehensive flow-sediment factor in the Middle Yangtze River was derived. Based on this relationship, Zhang’s sediment transport capacity formula was improved with its parameters being calculated according to varying flow and sediment conditions. Then the improved sediment transport capacity formula was successfully applied to other rivers with low sediment concentrations, also including a 347-km-long reach of the Middle Yangtze River.