Hydrodynamic Characteristics And Nutrient Transport Of Overland Flow Under Plant Covering Condition

Water erosion is the most harmful form of soil erosion in chin.Overland flow is the main driving factors of water erosion and non-point source pollution.Herbaceous plants can affect soil characteristics and hydrodynamic characteristics of overland flow.This paper researched the effect of herbaceous plants on erosion process and overland flow hydraulics characteristics by Field simulation scouring test,and studied the influence of herbaceous plants on nutrient transfer mechanism through indoor simulated rainfall.The results showed:(1)Herbaceous plants could reduce the amount of erosion,and the effect of row arrangement plants on erosion was more effective than random.The dynamic changes of erosion modulus was increased and then decreased.The change amplitude increased with the plant density increase,and the changing trend of plant random arrangement slope was gentler than the row arrangement slope.(2)Herbaceous plants could reduce the turbulence and the kinetic energy of overland flow.The effect of plant arrangement on Reynolds number and Froude number was non-significant.The Reynolds number increased with time,and the rate of change increased with the plant density increase.Froude number decreased with the of plant density increase.The dynamic changes of Froude number decreased slowly with time.And the effect of plant arrangement on the change was not significant.(3)The resistance coefficient of overland flow increased with the increase of plant density.However,the effect of plants increasing the resistance declined with vegetation decreased.The trend of resistance coefficient increased with scouring time was the power function,and the plant could effectively reduce variation amplitude of resistance coefficient.Dynamic changes of plant random arrangement slope were gentler than the plant row arrangement slope.Stepwise regression analysis ofresistance coefficient showed:f=2.350t0.012 Qoutflow-3.178C0.084,which indicated that dynamic changes of the resistance coefficient was closely related to the infiltration process,and has non-significant relation with the erosion process.(4)Plant could affect nutrient loss though controlling erosion process and the impact of underground part to control nutrient loss was more efficient than aboveground.Compared the effeect of two plants to control nutrient loss with eroded sediment,the effect of alfalfa aboveground part was better than green bristle grass for total nitrogen,which was not significant different from green bristle grass for total phosphorus and available potassium.The alfalfa underground part controlling total nitrogen,total phosphorus and available phosphorus loss was poorer than green bristle grass.(5)Herbaceous Plants could reduce the nutrient loss with runoff though controlling the infiltration process.Nutrient concentration of overland flow rapidly declined then gradually stabilized,which power function could well simulate for.Power function could simulate the changing process of nutrients concentration well and was more suitable to describe the process of non-point source pollution process.The complete plant and underground part could slow down the process of nutrient dynamic change(total nitrogen,available phosphorus and available potassium).However,the aboveground part could increase the change amplitude of total nitrogen and reduce it of total phosphorus,which was no significant effect for available potassium.