Influence Of Bedrock Ups And Downs And Karst Pipeline Morphology On The Process Of Soil Erosion In Karst Area

Dual system is well developed in karst landscape in southwest China,which leads to the soil and water loss occur both on the surface of ground and through underground vertical leakage.Bedrock relief and karst pipelines are two important factors affecting soil and water processed in karst areas.Based on the field investigation and through the simulated rainfall experiment,our study explored the effects of the bedrock relief,karst pipeline size,and rainfall intensity on soil and water loss at surface and the vertical leakage,characteristics of rainfall distribution and the particles in soil erosion.Our results provided scientific basis of soil and water conservation and rocky desertification control in karst regions.The main conclusions are as follows:(1)The influence of bedrock relief on the runoff-yielding time of the surface runoff,the vertical leakage and the flow at rock-soil interface is most obvious at the rainfall with 53 mm/h intensity.Specifically,bedrock relief could accelerate the initial flow time of the surface runoff and the vertical leakage,while extend the initial flow time at rock-soil interface.The time of surface runoff and vertical leakage on the underlying surface of bedrock relief is more than 20 min and 10 min earlier than that on the underlying surface of smooth bedrock,respectively.While the initial flow time at the rock-soil interface with unsmooth underly surface is about 5 min later than that of the smooth one.In addition,the size of the karst pipelines has no significant influence on the initial flow time.Generally,with the increase of rainfall intensity,the initial flow time of each treatment was advanced,while there was no significant difference.(2)The influence of bedrock relief on soil and water processes is mainly reflected in increasing the surface runoff and sediment yield,and underground runoff,reducing the underground leakage and the flow at rock-soil interface.The size of karst pipeline is positively correlated with underground runoff in the underlying surface of smooth bedrock,specifically,the underground runoff increases with the increase of pipeline aperture.It plays a leading role in underground sediment leakage when the bedrock connectivity is closed.Additionally,rainfall intensity is also an important factor affecting the process of soil and water loss.It has positively correlations with the surface runoff and sediment yield,leakage of sediment,and soil water storage,while the negatively correlation with the flow at rock-soil interface.Generally,the sediment yield at all part increased with the increase of rainfall intensity.(3)The erosion at the surface and underground are dominated by particles with dimeter < 2 mm,the content of which on the surface and underground is 89.87% and 83.34%,respectively.Bedrock relief can increase the content and enrichment rate of the particles with diameter < 2 mm of the surface and the underground.In the case of disconnected bedrock,with the increase of the karst pipeline aperture,the vertical leakage of the particles with diameter < 2 mm present an increasing trend.(4)According to the above,we conclude that the main driving factors of soil erosion at surface are rainfall intensity and bedrock relief,and the main driving factors of vertical leakage are rainfall intensity and the size of karst pipeline.The flow at the rock-soil interface is mainly affected by bedrock relief.