Study On Water-sand Process And Soil Erosion Dynamics Characteristics Of Covered Slope Under Artificial Simulated Rainfall Conditions

Soil erosion is one of the environmental problems in the world.All countries have different degrees of soil erosion,but China is one of the countries with the most serious soil erosion in the world.Yongding river upstream basin is located in the semi-arid sub-humid Mongolian plateau and north China plain transition zone,is the typical area in semi-arid sub-humid ecosystem in China,the regional vegetation condition is bad,much less rainfall and its uneven distribution in time and space,there is a mountain vegetation de-struction,poor function of water conservation,the river sediment concentration,such as shortage of sur-face water resources functional problem,serious soil erosion condition,greatly influenced the regional ecosystem balance.Therefore,it is necessary to study the process and mechanism of soil erosion,water and sediment for the restoration and reconstruction of ecosystem and the benign construction of ecological environment in the upper reaches of yongding river.This study in the typical regions-yongding river upstream qingshui river basin as the study area,using the research method of indoor artificial rainfall simulation system condition analysis of qingshui river basin different cover(bringing,pure,pure grass and the bare slope)and the conditions of different rainfall intensity(30 mm/h,45 mm/h,60 mm/h/h,90 mm and 75 mm/h)of the slope surface water and sediment transport process and the characteristics of the hydrodynamics and then analyze the response of the slope soil erosion mechanism and internal mechanism,thought of yongding river upstream basin soil erosion rule research provides the theoretical foundation,It provides theoretical basis for ecosystem restoration and green development of the upper reaches of yongding river.The main conclusions of the study are as follows:(1)the sediment yield process of slopes with different rainfall intensity and different cover conditions was analyzed.The slope runoff yield first increased and then tended to be stable with time,and the slope sed-iment yield first increased and then decreased with time.Under different rainfall intensities of the same cover,runoff rate and sediment yield increased with the increase of rainfall intensity.Under the same rainfall intensity and different cover conditions,the runoff rate and sediment yield of the irrigation and grass group were the lowest,followed by pure grass,pure irrigation and bare slope.There was a good positive correlation between cumulative sediment yield and cumulative runoff under each cover condition.(2)the variation law of hydrodynamic parameters of slope under different rain intensity and different cover conditions was analyzed.Vegetation coverage has a good deceleration effect on slope flow,and the deceleration effect under each cover condition is:pure irrigation>pure grass>irrigation grass;The order of average runoff depth on slopes with different coverings was as follows:pure grass>irrigated grass>;pure grass>irrigated bare slope;The range of Reynolds number of runoff under different cover conditions was 2.25-42.65,all of which were laminar flows.Froude values range from 0.20 to 0.88,which are all slow flow.Correlation analysis shows that manning roughness coefficient and drag coefficient are nega-tively correlated with sediment yield.(3)the dynamic mechanism of slope flow erosion under different rainfall intensity and different cover conditions was analyzed.Under each cover condition,with the increase of rain intensity,the erosion ki-netic parameters would increase accordingly.The average runoff shear force of the slope under different cover conditions was:>pure grass>bare slope;The average runoff power was>pure grass>pure grass>bare slope.The average unit runoff power was as follows:bare slope>grass>pure grass>pure grass;The order of unit energy of average section is:pure irrigation>,pure grass>,bare slope of grass>.The dy-namic parameters of erosion under each cover condition showed a good linear correlation with the sedi-ment yield under the corresponding conditions.Therefore,soil erosion in this region is affected by rainfall intensity and cover.The greater the rainfall intensity is,the more severe the erosion will be.Vegetation cover can effectively mitigate soil erosion.