Abstract:The development of plunge pool is a key process of headcut erosion. To clarify the effect of headcut height on the developmental processes and dynamical mechanisms of plunge pool. The study investigated the developmental processes and dynamical mechanisms of plunge pool under different headcut heights (25 cm, 50 cm, 75 cm, 100 cm, and 125 cm) on a granite red loam slope. The results show that: (1) As the height of the headcut increases, the Re, τ, ω and the jet parameters: Vbottom, , Ekbottom, and show an increasing trend. (2) After the laterite soil layer scouring to form a "V" type of small plunge pool mainly, with the increase in the flow of the form of plunge pool gradually increased, but it is difficult to form a large area of the plunge pool, and the laterite soil layer is more stable than the sandy soil layer. During the scouring process of the sandy soil layer, the development of headcut bed drop points was more obvious, and when the flow rate increased to 120 L/min, the degree of headcut bed fragmentation was gradually drastic, and the outline of the drop points was gradually clearer, and the cross-sectional area increased (3) The study characterizes the degree of erosion of drop caves through cross-sectional area. Random forest algorithm and Shapley values are used to construct the model and characterize the relationship between the parameters. The results showed that in the laterite layer, Fr, ω, Ekbrink, and Re were negatively correlated with the cross-sectional area; and in the sandy soil layer, Fr and were negatively correlated with the cross-sectional area. Higher accuracy of predictive models constructed by the random forest algorithm (LCCC=1.02, R2adjusted=0.876 and 0.868). The study provides a theoretical basis for revealing the mechanism of plunge pool development, improving the theoretical system of gully erosion, and preventing and controlling soil erosion in the red soil area.