High-precision simulation of runoff–sediment is a significant challenge due to the combined impacts of climate change and human activities. In this paper, runoff–sediment processes were simulated, and their impact attribution was analyzed using the Soil and Water Assessment Tool (SWAT) model in the upper Fenhe River basin of the Loess Plateau, China. A SWAT model was constructed to assess its applicability during the historical baseline period, which reflects low human activity. However, the simulation results for the comprehensive impact period, using the calibrated historical baseline model, were unsatisfactory. Consequently, a method was proposed to enhance the accuracy of simulation results by considering the presence of soil-retaining dams. This method incorporates large and small soil-retaining dams as reservoirs and ponds, respectively, into SWAT. The results indicate that the accuracy of runoff and sediment simulation reaches a satisfactory level. The attribution analysis results show that human activities have a greater impact on runoff and sediment than climate change, with land use change and soil-retaining dams being particularly significant. The construction of soil-retaining dams plays a more significant role in reducing runoff and sediment. These findings provide valuable insights into the management and utilization of runoff and sediment in river basins.

  • The incorporation of soil-retaining dams into the Soil and Water Assessment Tool is proposed to improve the runoff–sediment simulation accuracy.

  • The accuracy of runoff–sediment simulation has been improved and reaches a satisfactory level.

  • The impact of land use change and soil-retaining dams on runoff–sediment is more significant than climate change.

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