The Slope Soil Erosion Process Under Different Rain Types And Its Quantitative Relationship With Soil Erodibility

In order to explore the effects of different rain types on the runoff and sediment yield process of slopes and the quantitative relationship between the factor(aggregate stability)of soil erodibility and slope erosion,the paper takes two typical types of cinnamon soil in the rocky mountainous area of Northern China as the research object and take a way combining indoor simulated rainfall and LB method for determining the stability of soil aggregates to analyze the slope erosion process under fixed and different combinations of rainfall intensities.Based on the WEPP rill and interrill erosion model framework,the erodibility factor,Ki and Kr was replaced by the modified characteristic parameter of aggregate stability Ka,and then establish erosion prediction equations of different particle sizes through regression analysis.The main conclusions are as follows:(1)Soil organic matter content and porosity are significantly correlated with the average weight diameter of aggregates,and the correlation coefficients are between 0.35?0.74 and 0.39?0.71 respectively.There is significant difference among the stability of aggregate in different particle sizes,and the particle size of agglomerates 1s smaller,the stability is better.The degree of damage to aggregates from large to small by different ways of LB method is:fast wetting(FW)?wetting stiring(WS)?slow wetting(SW)and it indicates that the sudden increase of internal pressure of the soil makes the slaking effect on the.aggregate burst and the mechanical shock from the outside is the main mechanism for the destruction of soil aggregates in the rocky mountainous areas of Northern China.(2)Both runoff intensity and sediment yield increase with the increase of rainfall intensity and rainfall duration under conditions of fixed rain intensity.The erosion process presents a obvious "three-stage",and headward erosion is the most important factor affecting the formation of rills.Due to differences in the nature of the two soils,the main erosion process of loess brown soil erosion is headward erosion and side wall collapse,while the limb drab so1l 1s dominated by the undercut to the ditch bottom of runoff and the headward erosion.(3)The yield of flow from high to low under four types of different rain intensities are 120-30-120 mm/h>90-60-30 mm/h>30-60-90 mm/h>30-l 20-30 mm/h while the order of the yield of seidment are 120-30-120 mm/h>90-60-30 mm/h>30-60-90 mm/h>30-120-30 mm/h.The headward erosion under the combination of variable rain intensity is still the primary factor for the development of rills,and the growth rate and maximum groove length of 120-30-120 mm/h are the biggest.(4)Under the condition of fixed rainfall intensity,the erosion prediction equation corresponding to each particle size of aggregate can accurately predict the amount of erosion on brown soil slope(R2>0.81),among them,the 2?3 mm particle size aggregate equation has the best prediction effect,and its average prediction relative error is below 16%both on the prediction of rill and interrill erosion.The prediction effects of the erosion equations under the four combinations of different rain intensity from good to bad are 120-30-120 mm/h?30-60-90 mm/h?90-60-30 mm/h?30-120-30 mm/h,and the effect of interrill erosion prediction is better than rill erosion.