| As is known to all,karst has a special dual hydrological structure,with the coexistence of surface soil erosion and underground leakage,resulting in a more complex process and mechanism of water and soil loss.At present,soil and water loss of karst areas has become a hot and difficult issue of soil and water conservation research at home and abroad.In karst areas,due to the complex topography and large population,slope takes up a large proportion of the land area,and most of them become shallow soil slope because of the serious water and soil loss,which leads to the surface soil thinning or the rock exposure.Although people have carried out some studies on the problem of water and soil loss in karst slopes,but there are few studies on thin soil slopes,which has an adverse effect on people's understanding of the occurrence and development of rocky desertification.the article adopted the way of simulated rainfall experiment,with Rocky Desertification thin soil slope as the research object,researches the characteristics that rainfall transformation became surface runoff,subsurface flow,rock-soil interfacial flow,underground fissure flow and soil erosion under the different situations in rainfall intensities,slope and the number of rainfall,reveal the process and mechanism of water and soil loss of karst rocky desertification slope.The research results have theoretical and practical value for water and soil conservation in Karst region.The main results are following:(1)The influences of rainfall intensities,slope and rainfall times on contributing time of surface runoff,subsurface flow,rock-soil interfacial flow and underground flow are different.For the none underground fissure slope,the surface contributing time decreased with the increase of rainfall intensities,slope gradient and rainfall times;the contributing time of subsurface flow decreased with increased of slope gradient and rainfall times;the contributing time of rock-soil interfacial flow decreased with increased of rainfall times.For underground fissure slope,the contribution time of surface runoff and subsurface flow decreased with increased of rainfall intensities,slope gradient and rainfall times;the contribution times of underground fissure flow decreased with increased of rainfall intensities and rainfall times,with increased of slope gradient,the contributing time increased.The results show that the responses of runoff to rainfall were different.(2)The surface runoff yields of two slope increased with increased of rainfall intensities,slope gradient and rainfall times.When the rainfall intensities were75 and 100 mm/h,the subsurface flow yields was greater than that the rainfall intensities was 50mm/h,the subsurface flow yields with increased of slope gradient,with increased of rainfall times,the subsurface flow yields of none underground fissure slope increased first increased and then decreased,the subsurface flow yields of underground fissure slope decreased.The yields of rock-soil interfacial flow and underground fissure flow first increased and then decreased with increased of rainfall intensities and rainfall times,the rock-soil interfacial flow and underground fissure flow yields of 15°and 25°slope were less that the slope gradient was 5° slope.The surface sediment yields increased with increased of rainfall intensities,slope gradient and rainfall times.But in all the rainfall experiments,the subsurface flow,rock-soil interfacial flow and underground fissure flow had not sediment,It shows that the mechanism of underground soil leakage was different from that of surface hydraulic erosion-transport process.(3)The rainfall intensities,slope gradient and rainfall times had effect on rainfall transformation.When rainfall intensities were 50 and 75 mm/h,more 22% rainfall transformation formed rock-soil interfacial flow of none underground fissure slope,more 18% rainfall transformation formed underground fissure flow of underground fissure slope;but rainfall intensities was 100 mm/h,more 41% rainfall transformation formed surface runoff in two slope.When slope gradient was 5°,in none underground fissure slope,more 50% rainfall transformation formed rock-soil interfacial flow,in underground fissure slope,more 61% rainfall transformation formed underground fissure flow,but with increased of slope gradient,rainfall transformation main formed surface runoff and subsurface flow,it accounts for 15.45%-20.42% and 26.36%-29.10% of the rainfall,respectively.For none underground fissure slope,more 39% rainfall transformation formed rock-soil interfacial flow at the first and second times rainfall,however,more 44% rainfall transformation formed surface runoff and subsurface flow at the third time.For underground fissure slope,more 51% rainfall transformation formed underground fissure flow among three times rainfall.Therefore,the rock-soil interfacial fissure changed rainfall transformation mechanisms of slope,rainfall transformation mainly formed rock-soil interfacial flow in none underground fissure slope,while rainfall of underground fissure slope mainly formed underground fissure flow.(4)The rock-soil interfacial flow had effect on rainfall transformation and soil erosion.With compared to underground fissure slope,the surface runoff yields and subsurface flow yields of none underground fissure slope increased 7.28%-270.41% and-24.75%-73.88%,respectively.The surface sediment yields increased 7.35%-294.69%.Therefore,rock-soil interfacial fissure changed process of runoff and soil erosion. |
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