Significant advancements have been made in vegetation restoration and ecosystem rehabilitation on the Loess Plateau, China. Previous studies have mainly focused on runoff and erosion in different vegetation types (trees, shrubs, and herbaceous plants), with few studies using hydrodynamic parameters to explain the flow and sediment reduction effects of the tree canopy, litter layer, and root layer. Using an artificial soil tank, the runoff and sediment yields of vegetation at each level (litter layer (LL), canopy layer (CL), bare soil layer (RL), and composite layer (litter + canopy) (SC)) were investigated under different rainfall intensities (RI) (30 and 90 mm/h) and slopes (S) (10 degrees and 15 degrees). The effects of hydrodynamic parameters on erosion were analysed by the structural equation model. The runoff rate of RL was the highest, with an average value of 0.37 L/min (RI: 30 mm/h; S: 15 degrees). The litter and composite layer had the greatest reduction effects on slope erosion (75.66%-92.94%), whereas the reduction rate of slope erosion by the canopy layer was 14.27%-63.94%. Under different rainfall and slope conditions, the cumulative runoff of RL was the largest. Except at an RI of 30 mm/h and an S of 10 degrees, the cumulative runoff of LL plots was the smallest, indicating that litter plays an important role in reducing slope runoff. Based on the structural equation model, the influence coefficients of the Froude number (Fr) on runoff and erosion are -0.28 and -0.31, respectively. This study provides quantitative evidence for optimising vegetation allocation strategies and a scientific basis for ecological protection in the Yellow River Basin.