Influencing Factors Analysis And Numerical Simulation On Erosion Of Yellow Soil In Southwest Karst Area, China

Climate,vegetation,soil,topography and human activity are the main influencing factors of soil erosion,there are different contributions of various factors in different regions on soil erosions.This paper chooses the karst area in southwest China as the research region. The slope(6°,16°,26°,36°),vegetation crown density(0%,40%,70%), rocks crown density(0%,30%,60%) and rainfall intensity(27mm/h,40mm/h,60mm/h,114mm/h) were determined as the erosion influencing factors of yellow soil for this simulation study by the analysis of material and fieldwork in the karst area of southwest China,Meanwhile,an equipment of imulated rainfall was designed which could fulfill the range of rainfall intensity in this area.Taking yellow soil as testing soil,144 processes of soil erosion simulation tests were done by intercombination of all refered factors.Results are as follows:The change trend of runoff ratio increased fast at first,reached the summit between 180-300s and then kept steady under every combination. Runoff ratio of soil surface increased with the increase of rainfall intensity and vegetation crown density,however,the runoff ratio increased at first then decreased with the increase of slopes,kept steady with the increase of rocks crown density,while it decreased with the increase of vegetation-rocks rate under every different combination.Total runoff hardly changes under every different combination of the same rainfall intensity.The change trend of transport rate of sediment yield could be divided into five periods:increase rapidly,decrease fast,increase,decrease and keep steady.Transport rate of sediment yield increased as the same as rainfall intensity under every different combination.It increased with the increase of slopes,decreased with the increase of rocks crown density under every different combination of bare soil and vegetation-covered soil.It increased at first then decreased with the increase of slopes when rainfall intensity is 27mm/h,40mm/h or 60mm/h,and it increased with the increase of slopes when rainfall intensity is 114mm/h under every different combination of vegetation-covered.And it increased at first then decreased with the increase of slopes,decreased with the increase of vegetation-rocks rate under every different combination of vegetation-rocks covered soil.Total sediment yield increased with the rainfall intensity under every different combination of vegetation-rocks covered soil.It increased with the increase of slopes under every different combination of rocks-covered soil and bare soil.It decreased with the increase of vegetation crown density,rocks crown density,vegetation-rocks rate under every different combination of vegetation-covered soil,rocks-covered soil and vegetation-rocks covered soil.It increased at first then decreased with the increase of slopes under vegetation-rocks covered soil and vegetation-covered soil wich rainfall intensity is 27mm/h,40mm/h or 60mm/h.And it increased with the increase of slopes under vegetation-covered soil when rainfall intensity is 114mm/h.The relevance is tight between cumulation of runoff rate,sediment yield and time.