Regularity of sediment transport and sedimentation during floods in the lower Yellow River, China

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The flood season is the main period of flow, sediment transport, and sedimentation in the lower Yellow River (LYR). Within the flood season, most of the flow, sediment transport, and sedimentation occurs during flood events. Because of the importance of floods in forming riverbeds in the LYR, the regularity of sediment transport and sedimentation during floods in the LYR was studied. Measured daily discharge and sediment transport rate data for the LYR from 1960 to 2006 were used. A total of 299 floods were selected; these floods had a complete evolution of the flood process from the Xiaolangdi to the Lijin hydrological stations. For five hydrological stations (Xiaolangdi, Huayuankou, Gaocun, Aishan, and Lijin), a correlation was first established for floods of different magnitudes between the average sediment transport rate at a given station and the average sediment concentration at the closest upstream station. The results showed that the sediment transport rate at the downstream station was strongly correlated with the inflow (upstream station) sediment concentration during a flood event. A relation then was established between sedimentation in the LYR and the average sediment concentration at the Xiaolangdi station during a flood event. From this relation, the critical sediment concentrations were obtained for absolute erosion, sedimentation equilibrium, and absolute deposition during floods of different magnitudes in the LYR. The results of the current study contribute to a better understanding of the mechanisms of sediment transport and the regularity of sedimentation in the LYR during floods, and provide technical support to guide the joint operation of reservoirs and the regulation of the LYR.