Abstract: Objective To explore the influence of vegetation coverage on hydrodynamic parameters of slopes of engineering accumulations during the construction of large-scale water resource allocation projects, and to provide theoretical support for the design of soil and water conservation measures for the ecological management of engineering accumulations. Method Taking the engineering accumulation of the large-scale water resource allocation project in Yong chuan District, Chongqing as the research object, field observations and runoff scouring tests were conducted. Three gradients of vegetation coverage (low: 4%, medium: 34%, high: 64%) and an inlet flow rate of 6 L/min were set to study the response mechanism of different vegetation coverage levels to hydrodynamic parameters. Result (1) The flow velocity of the low-vegetation-coverage slope increased linearly with runoff scouring. The Reynolds number (<italic>Re</italic>) ranged from 1715.97 to 3402.31, and the flow regime showed an overall transition from transitional flow to supercritical turbulent flow. (2) The flow velocity and drag coefficient of the medium-vegetation-coverage slope changed nonlinearly; the peak flow velocity reached 0.42 m/s at the initial stage, and the <italic>Re</italic> value was generally high, showing a parabolic variation trend with the extension of scouring time. The Froude number (<italic>Fr</italic>) of the medium-vegetation-coverage slope was significantly higher than that of the low-coverage slope (<italic>p</italic>=0.008) and high-coverage slope (<italic>p</italic>=0.033). (3) The flow velocity of the high-vegetation-coverage slope showed a U-shaped curve trend. After a short period of scouring, the <italic>Re</italic> value of the high-vegetation-coverage slope decreased significantly (R²=0.906), and the drag coefficient showed a "first increase then decrease" trend. (4) Linear fitting indicated a negative correlation between the drag coefficient and Reynolds number, and the power function achieved the best fitting effect. Conclusion Differentiated vegetation allocation strategies should be adopted for the ecological management of engineering accumulations, and the coverage threshold should be comprehensively considered to balance runoff regulation and erosion resistance stability. The research results provide a hydrodynamic theoretical basis for the design of soil and water conservation measures for engineering accumulations in production and construction projects.