Characteristics of aggregates with different particle sizes and their effects on slope erosion process in the rocky mountainous area of north China
[Objective]The aims of this study are to investigate the process of slope erosion under different rainfall patterns,to elucidate the quantitative relationship between the stability characteristics of agglomerates and slope erosion,sand to provide theoretical basis for soil erosion management in the rocky mountainous area of north China.[Methods]LB method was used to analyze two typical lignite soils(calcareous lignite and loess lignite)with particle sizes of less than 2 mm,2～3 mm,3～5 mm,5～7 mm,and more than 7 mm.Four rainfall types(intensification,weakening,valley value,and peak value)were designed to analyze soil erosion processes under different rainfall patterns,and the characteristic parameter Ka for the stability of agglomerates of each particle size was substituted for the corrosivity factor Kiin the WEPP model to calculate the predicted values.The applicability of the model was assessed by comparing the simulated and measured values using the Nash-Sutcliffe validity(E).The impact of aggregate stability on the process of soil erosion under these different rainfall types was also examined.[Results]A comparison of the stability of big and small particle size range aggregates under the three method treatments revealed that the stability of two types of soil aggregates was lower for the size of fast wetting,wetting shock,and gradual wetting,the most stable aggregates were those with particle sizes between 2 and 3 mm,and the aggregates made of loess brown soil had less stability than those made of calcareous brown soil.With 1.6 and 1.3 times the runoff and sand production of the peak type,the total quantity of runoff and sediment production on the valley type's slope was the highest under the various rainfall kinds.The runoff intensity and the rate of sediment production were significantly impacted by the same rainfall intensity that fell at different times.Specifically,the runoff intensity and the rate of sediment production were higher in the early stages of the peak and valley types,and sediment production rate of the loess brown soil were greater than the calcareous brown soil.The results demonstrated that the aggregate particle size had a better simulation effect on the downslope erosion of both strengthened and weakened rainfalls.The aggregate particle size of 3～5 mm had the best simulation effect,and the computed effectiveness value was greater than 0.8.[Conclusion]The simulation effect of measuring soil corrosivity characteristics with the stability of aggregates of different grain sizes is better,and this can serve as a reference for the assessment of the efficacy of soil and water conservation in the rocky mountainous area of north China.
particle sizeaggregate stabilityrainfall patternsoil erosionrunoff and sediment
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