| In recent years,under the influence of climate change,extreme weather has occurred globally,and soil erosion disasters caused by heavy rainfall have shown an increasing trend.Severe soil erosion can destroy arable land resources,raise riverbeds and silt reservoirs,increase flooding potential,and pose a serious threat to the world’s food security and ecological safety.Therefore,in order to simulate the soil erosion process in the Loess sub-basin under heavy rainfall,and to identify the response mechanism of topographic changes to rainfall and soil conservation measures in the Loess sub-basin under heavy rainfall,this study uses a physical sub-basin model,combined with traditional water and sand observation and terrain 3D laser scanning technology,to carry out indoor simulated rainfall In this study,we used a physical watershed model,combined with traditional water-sand observation and terrain 3D laser scanning technology,to conduct an indoor rainfall simulation,simulated the erosion process of flash floods in a small loess watershed,quantified the erosion evolution stages of the watershed using geomorphological information entropy theory,analyzed the spatial distribution pattern of soil erosion-deposition in the watershed,and quantitatively described the effects of rainfall intensity and silt dam placement on the topography of the watershed.The results of the study show that:(1)3D laser terrain scanning technology can achieve accurate measurement of spatial distribution of soil erosion-deposition in small watershed models,and can clearly identify the spatial distribution of erosion-deposition in small watersheds in response to rainfall and soil conservation measures deployment by tracking the evolution of small watershed geomorphology under simulated rainfall conditions.(2)Under the action of small to medium rainfall intensity(30-60mm/h),the intensity of erosion and deposition occurring in the loess sub-basin is mainly mild,i.e.the erosion depth and deposition thickness is within 10 mm,and the construction of silt dam can play a good role in water storage and soil preservation.Siltation dam can effectively intercept the sediment carried by the runoff in front of the dam on the one hand,and regulate the scale of the runoff behind the dam on the other hand,thus reducing the erosion intensity of the gully behind the dam.(3)Under the effect of extreme heavy rainfall(120mm/h)with large rainfall intensity,the proportion of moderate,severe and serious soil erosion-deposition will multiply regardless of whether silt dams are deployed in small watersheds.Therefore,in small watersheds,soil and water conservation measures can perform better soil and water conservation functions under moderate and small rainfall intensities,but their ability to store water and retain sand will be reduced under extreme heavy rainfall intensities,so rainfall is the dominant factor triggering severe soil erosion disasters.(4)Under the action of rainfall,the geomorphic information entropy can well quantify the erosion and deposition phenomena of soil,and the geomorphic information entropy value of the area where erosion occurs will become larger,and that of the area where deposition occurs will become smaller.However,from an overall perspective,the geomorphic evolution process of the strong-aged subwatersheds under the action of rainfall is in accordance with the entropy increase principle toward a more stable old age.This study will provide a theoretical basis for the study of soil erosion-deposition patterns and the construction of erosion forecasting models in loess sub-basins,as well as a scientific basis for the identification of key soil erosion sites in loess areas and the scientific deployment of soil and water conservation measures. |
