Sediment transport characteristics at the flood-event scale in the Minjiang River Basin, China

In recent years, the significant change in the runoff-sediment distribution in the upper Yangtze River has led to an increased sediment contribution from the Minjiang River Basin (MRB) to the Three Gorges Reservoir. However, previous studies on sediment load changes in the MRB have focused mainly on annual-scale characteristics, thereby neglecting features driven by floods. Therefore, this study focused on examining the changes in flood-event sediment loads in the MRB based on mathematical statistics and comprehensive measurement data. The results indicated that human activities, climate change, and seismic events have caused an increasing trend in the flood-scale sediment load in the upper MRB and a decreasing trend in the lower MRB. The changes in the flood-scale sediment modulus at low runoff erosion power levels were greater than those at high runoff erosion power levels at different abrupt-change stages. During extreme flood events, the actual sediment concentration in the MRB remained below the sediment-carrying capacity. This study provides novel insights into water resource management during the flood season in the MRB and similar basins. HIGHLIGHTS Changes in the sediment load at the flood-event scale show opposite trends upstream and downstream of the Minjiang River Basin (MRB). After an abrupt change, the variation in sediment transport is smaller under high-flow conditions than under low-flow conditions. Under extreme flood conditions, the actual sediment concentration in the MRB does not reach the sediment-carrying capacity.