Estimation Of Soil Erosion In Small Washed Of Karst Upland Based On GIS

Rocky desertification is the final stage of soil erosion in karst area.In the karst area of Chongqing,there are distinguished differences between downslope and upslope on erosion characteristics and influence factors.Therefore,make a study of soil erosion characteristic and influence factors in agricultural area of Karst Mountains,take on great importance to degraded ecosystem restoration and water and soil erossion prevention of Karst Mountains in Chongqin.This paper takes the small washed of Muduhe located in Karst ecological fragile area in Chongqing as an example,trying to analyze the characteristic of soil erosion on distribution of grade,different land use and different grade,which based on the date of rainfall,DEM,soil and rocky desertification,and introduction of rocky desertification factorαin RUSLE by using GIS and modified RUSLE.Besides,it also evaluated the potential soil erosion and discussed the capability of soil conservation of land use types;Had a simulation on controlling measures of soil erosion and verified the results after changing the controlling measures of soil erosion in the Muduhe small watershed.The conclusion is as follows:(1) The average soil erosion modulus of the Muduhe small watershed is 1804t/km~2·a,which belongs to the light erosion.In the Muduhe small watershed that above the srong erosion area is only accounts for 8.97%of total watershed area,but the amounts of soil erosion accounts for 35.06%of the total watershed amounts.The reason why this area is sloping land that strongly intervened by human activities,which needs taking emphases management.(2) From the perspective of the ratio of erosion amount,the sloping land takes the largest proportion which accounts for 81.07%of total erosion amounts,young forest accounts for 7.30% following sloping land.Other land-use types account for a comparatively small proportion.So we may come to a conclusion that sloping land is the main land-use types impact soil erosion in Muduhe small watershed.(3) The area of strong erosion and extremely strong erosion is mainly distributing over 15～25°and 25～35°,and the largest soil erosion amount distrubut between 8°and 25°,which takes a proportion of 80.86%of the total area.So we get that land-use types between 8°and 25°was the source of soil and water loss in Muduhe small watershed.(4) In Muduhe small watershed,the annual average potential soil erosion modulus is 39506t/km~2·a,and its total annual potential soil erosion is 8.76×10~5t,with the average capability of soil conservation as 20.89.Muduhe small watershed has a stronger capability of soil conservation. From the difference of land-use types,we may see that the sloping land and paddy field have a largest amount of potential soil erosion,the young forest,woodland and spinney have a largest soil conservation in unit area;and from the capability of soil conservation,we may see that the paddy field has the greatest capability of soil conservation which can attain 554.55,the waste grassland and sloping land whose capability of soil conservation is the lowest.(5) The leading factor of the soil erosion is land-use types in Muduhe small watershed,so the key measurement is to adjusting the structure of the land-use types,the way is proper changing the land of vegetation coverage low and poor management.The paddy field,terracing,sloping and economic fruit forest that have been regulated is respectively 753.55 hm~2,85.96 hm~2,336.06 hm~2 and 408.37hm~2,with the proportion of 1:0.114:0.446:0.542.As for the sloping above 25°and waste grassland,we tend to use water conserved forest,while young forest we tend to use blockading administration and repair planting,which can enhance the combination of tree,shrub and grass,thus strengthen the function of soil and water conservation.(6) Through using simulation of controlling measures of soil erosion,the change of soil erosion amount is visible in the Muduhe small watershed.The average soil erosion modulus is reducing to 1180 t/km~2·a which decreased by 34.59%,and annual soil erosion amount is reducing to 26173.73t/a. That is to say,the advantage of measure of soil erosion is obvious.