Comparative Experimental Study Of Two Typical Loess Terrain Development And Erosion Law On Slope

The development of rills shapes complex rills and enhances the runoff erosion energy of slopes.The increase of runoff erosion energy on slopes accelerates the development of rills.Therefore,it is important to study the development of rills on the slope,the morphological characteristics of rills,and the law of rill erosion to reveal the mechanism of soil erosion.The paper uses indoor artificial rainfall simulation,3D laser scanning,high-definition photography and other methods.The cultivated loessial soil and dark loessial soil soil in the loess area are taken as the research object,and the two rain intensity conditions of 60 mm/h and 90 mm/h are selected for the 20° slope.Three simulated rainfall tests with a duration of 1 h were performed.The development of the rills on the slopes of the two soils and the effects of rill development on the runoff and sediment yield process on the slope were investigated;The temporal and spatial evolution of morphological parameters of rills on slopes and the effects of morphological evolution of rills on erosion and sediment yield on slopes are analyzed;The relationship between morphological parameters of rills was studied;the law of rill erosion was revealed.The main conclusions are as follows:(1)Exploring the influence of the development of rills on the slope and the process of sediment yield.The characteristic parameters of the fine groove network(fine groove density,fine groove bifurcation ratio,and fine groove merge point)increased in the first two fields,and the third field of rainfall decreased.The development of the fine groove network experienced from simple to Complex to simple process.The ridge ditch on the slope of black shoal was earlier than the loess soil for more than 9 min.The characteristic parameters of the first rain sluice network exceeded 1.31 times of that of loessial soil.The characteristic parameters of the second ridge ditch network exceeded 1.16 times of that of black loess.The rills on the slopes of the dark loessial soil are early and slow to develop,while the rills on the slopes of the cultivated loessial soil are late and develop rapidly.During the generation and development of rills,the process line of slope runoff remained stable,and the process of sediment yield on the slope appeared to fluctuate greatly.The occurrence and development of rills had no obvious effect on the runoff process of slope,but the sediment yield on slope The process has a significant impact.(2)The influence of morphological evolution of rills on slope erosion and sediment yield was analyzed.With the development of the rill,the average width,average depth,and contour deviation of the sloping surface increase with the rainfall duration,but the cumulative length of the rill increases first and then decreases.With the increase of slope length,the average width of the rill,the average depth,and the deviation of the contour line of the slope appear to fluctuate greatly.The average width and average depth of the rill are similar along the slope length,and the morphological characteristics of the rill vary along the length of the slope.It indirectly reflects the increase and decrease of erosion energy along the slope runoff.There is a linear correlation between morphological parameters and sediment concentration.The correlation coefficient of loess soil is greater than 0.93,and the correlation coefficient of black loess soil is greater than 0.75.The evolution of rill morphology will inevitably lead to the change of sediment concentration on slope.The cultivated loessial soil has low clay content and poor overall stability.The response of slope sediment to morphological evolution of rills is stronger than that of dark loessial soil.(3)The relationship between the rill shape parameters was analyzed.The cumulative length of the fine groove is related to the average width and average depth of the fine groove.The correlation coefficient is greater than 0.81.The average width of the fine groove and the average depth are linearly correlated,and the correlation coefficient is greater than 0.85.As the rill develops,the changes in the length,width,and depth of the rill are not independent,but are processes that are interconnected and interact.(4)Contrast and explore the erosion law of rills on two kinds of soil slopes.The contribution rate of rill erosion in cultivated loessial soil is less than 30% in the first rainfall,and the rainfall in the latter two is more than 85%.The contribution rate of rill erosion in the dark loessial soil is less than 56% in the first two periods and more than 70% in the third period.The gully erosion of the cultivated loessial soil intensified in the second rainfall,but the erosion of the shoal of the dark loessial soil increased in the third rainfall.During the rill erosion process,the source erosion rate,the trench wall erosion rate,the groove bottom erosion rate and the slope rill erosion rate all have an exponential function,and the correlation coefficient is greater than 0.7.Cultivated loessial soil erosion three kinds of methods on the erosion rate is more consistent fine grooves,cut impact erosion erosion and collapse of trench walls ditch dark loessial soil erosion rate is higher than the traceability rill erosion.