Flood event sediment load plays a critical role in evaluating the effectiveness of soil and water conservation measures on the Loess Plateau and advancing understanding of water and sediment dynamics in the middle reaches of the Yellow River Basin. Thus, 524 flood events from 1960 to 2020 were analysed to identify the changes in flood event sediment load and their driving mechanisms in the Dali River Basin on the Loess Plateau, China. Results indicate that flood events consistently dominate sediment load, accounting for more than 90% of annual sediment load in most years. Two abrupt change points in the annual flood sediment load are identified in 1971 and 2002, accompanied by substantial declines in both annual maximum peak sediment concentration and flood sediment load across three periods. Runoff-sediment relationships become increasingly clustered with reduced slopes, indicating weakened sediment load sensitivity to runoff. Check dams, terraces, and vegetation exhibit significant negative relationships with flood sediment load, whereas five extreme precipitation indices are positively correlated (p < 0.05). These patterns suggest that although extreme precipitation remains a key hydrological driver of sediment mobilisation, its sediment-producing effect is increasingly constrained by soil and water conservation measures. Overall, coordinated implementation of check dams, terraces, and vegetation reduces sediment availability and connectivity within the basin, making sediment load during extreme flood events unlikely to exceed historical upper limits under current conservation conditions. The findings establish a scientific basis for sediment management and the optimization of soil and water conservation strategies.