Evaluation And Mapping Of Soil Erosion In The Pearl River Basin Based On GIS And CSLE Model

Soil erosion is a serious threat to the ecological environment and the sustainable development of the region,which hinders the healthy soil to provide normal ecosystem services,and has become an environmental problem concerned by many researchers at home and abroad.The Pearl River is the third largest river in China.Located in the South of the subtropical zone,The Pearl River Basin is humid and rainy,and the Karst landforms are widely distributed.The Pearl Delta,located in the lower reaches of the Pearl River Basin,is an important engine of China’s economic development.Compared with the North China,the research on soil erosion in the Pearl River Basin is relatively weak,in addition to the soil and water conservation monitoring bulletins,no form of overall and comprehensive understanding of whole basin.There is no publicly published map of soil erosion rate with higher resolution in the Pearl River Basin.At the same time,the potential danger of soil erosion in the Pearl River Basin is high,and the current research and treatment are not compatible with the prisperous economy of the Pearl River Basin,and can not satisfy the needs of water and soil conservation and ecological construction.Therefore,it is urgent to make use of modern science and technology to systematically study the soil erosion in the Pearl River Basin.Based on the CSLE model,this study used two methods,map algebra and spatial interpolation,to map the soil erosion in the Pearl River Basin(including Hainan Province and other regions),and analyzed the spatial pattern,main controlling factors and soil erosion sensitivity of soil erosion.The main conclusions are as follows:(1)The main characteristics of the study area are high rainfall erosive power,high vegetation coverage and steep slope.Soil erosion is affected by many factors,but the main influencing factors vary from region to region.Located in the south of the subtropical zone,the Pearl River Basin has high rainfall and good vegetation coverage,but the slope of the hilly area is steep.The high value of slope length factor can be seen in Yunnan-Guizhou Plateau,eastern mountainous region and Wuzhi Mountain in Hainan Province,which is the main inducing factor of soil erosion.Vegetation coverage in the study area is high,which is the main inhibiting factor of soil erosion.(2)Map algebra and spatial interpolation can be used to map soil erosion rate in the study area.In this study,two calculating methods,map algebra and spatial interpolation,were used to map the soil erosion rate in the study area.The mean values of soil erosion rate were 791.78t/(km~2·a)and 615.37t/(km~2·a),respectively,which were close to each other(the difference was less than half of the allowable loss in this area).Soil erosion was widely distributed in the study area,mainly concentrated in the coastal areas of Guizhou and Yunnan provinces,central Guangxi and Guangdong provinces,among which the area of intense and extremely intense erosion was small and distributed on scattered sloping farmland.Compared with the mapping results of map algebra and spatial interpolation,the spatial interpolation is more close to the actual situation of soil erosion,because the spatial interpolation method is based on the sampling survey unit to obtain more detailed and accurate imformation of soil and water conservation measures,it can be used as the first choice for mapping regional soil erosion.(3)Land use type is the main controlling factor of soil erosion.In the whole study area and each area of soil and water conservation regionalization,the order of influence degree of each factor from large to small is basically land use,water conservation measures(especially B factor),topography,soil and precipitation.Land use type is the main controlling factor affecting soil erosion rate.Generally speaking,soil and rainfall have little influence due to the high vegetation coverage in the study area.The interaction of the two factors is the synergistic enhancement of land use type and other influencing factors on the formation of soil erosion,which further indicates that land use type is the main controlling factor of soil erosion amount.(4)The mountainous and hilly areas of the Dianqiangui and the mountainous and hilly areas of Nanling are highly sensitive to soil erosion.The soil erosion sensitivity in the study area was mainly slightly sensitive.In the soil and water loss control management,Attention should be paid to the improvement of the soil structure in the mountainous and hilly areas of the Dianqiangui,We should concentrate on adjusting the gradient and slope length(e.g,)to change the terrain,in south China coastal hills in Taiwan and Hainan and the hilly region of the two,The occurrence of rainstorm events and the soild structure should be paid attention to,and the research of regional land use structure adjustment,etc.At the same time,the comprehensive control of soil and water loss should be considered in the mountainous and hilly areas of the Dianqiangui and the mountainous and hilly areas of Nanling.