Interpretation of soil erosion evolution characteristics in small Watersheds in Pisha sandstone area based on sedimentary information of check dam

Soil erosion inversion study is an effective means to evaluate the benefits of soil and water conservation measures. The check dam store rich information of erosion and sand production at the same time, which can better reflect the evolution characteristics of soil erosion in the watershed. At present, the research on the evolution characteristics of soil erosion in the arsenic sandstone area is relatively weak, which is difficult to meet the demand for high-quality development of soil and water conservation. In this study, the small dam of Lujiagou in Huangfuchuan watershed in the Pisha sandstonearea was selected as the research object, and the soil erosion evolution characteristics of the watershed were investigated by studying the correspondence between the sediment deposition information of check dam and the erosive force of rainfall from 2007 to 2022. The main conclusions are as follows: Based on the relationship between annual cumulative rainfall erosive power and annual cumulative siltation from 2007 to 2022, three stages were divided: 2007 to 2012, 2013 to 2017, and 2018 to 2022; the total erosion modulus for the three stages were 25652.45 t·km-2, 6071.32 t·km-2, and 26492.85 t·km-2, respectively. The average annual erosion modulus was 5130.49 t·km-2, 1214.26 t·km-2, and 5298.57 t·km-2, respectively. The rainfall erosivity in this subwatershed showed an increasing trend with the stage change, and the increase in rainfall erosivity was mainly caused by rainfall above 35 mm, and its increase in rainfall erosivity accounted for 149.87% of the total increase in rainfall erosivity and 105.6%, respectively. The modulus of soil erosion and the modulus of erosion per unit of annual rainfall erosivity at the three stages showed a decreasing and then increasing trend with the changes of the stages, in which the modulus of erosion per unit of annual rainfall erosivity at Stages II and III were lower than that at Stage I, which were 804.27 t•(MJ•mm)-1•h and 410.03 t•(MJ•mm)-1•h, respectively.Conclusion There is a threshold value for the ability of the vegetation to control the soil erosion, and the erosive force caused by the rainfall erosion force of the rainfall above heavy rainfall rises from 23.27 MJ·mm•hm-²·h-1 in Stage Ⅱ to 32.27 MJ·mm•hm -²·h-1 in Stage Ⅲ. 1 increased to 32.64 MJ·mm•hm -²·h-1 in stage III, the erosion modulus caused by annual unit rainfall erosive force increased from 178.2 t•(MJ•mm)-1•h to 572.45 t•(MJ•mm)-1•h. The results of the study can provide scientific references for the evaluation of the benefits of soil and water conservation measures in thePisha sandstonearea.