Comparative Study Based On The Different Evaluating Methods Of Soil Erosion In Lianshui Basin Of Red Soil Area

There were many soil erosion monitoring methods.However,research reports are rare in three aspects:1) what were the differences among these methods;2) which method can provide more accurate quantitative amount of soil erosion.On the basis of analyzing rainfall and terrain factors,this paper did research in the soil erosion state of Lianshui basin in Jiangxi Province through selecting three conventional methods of soil erosion monitoring,including RULSE model,visual interpretation and basin export observation.First,this thesis revealed the trend of rainfall erosivity in this basin.We found the differences among these models by selecting six different models of rainfall erosity which had been applied to red soil areas.Secondly,we analyzed the terrain factors through establishing two DEM which scales are 1:100000 and 1:50000 respectively,and found difference between two DEM.We obtained the quantitative estimating amount of the RUSLE model referring to the previous soil erodibility factor K value,vegetation factor C and measure factor P.Finally,we made maps of soil erosion intensity and land use by visual interpretation for five years including 1975,1991,1995,2000,2005.By these analyses above,the results were as follows:(1)The soil erosion area changed alternately high and low based on RUSLE model, and the soil erosion area reached up to be biggest in 2005.The soil erosion area reduced annually based on visual interpretation.The gap of erosion area ratio between RUSLE model and visual interpretation was 4.8%,-3.1%,13.8%,1.9%and 21.5%respectively.The soil erosion area based on RUSLE model was bigger than visual interpretation except 1991 in 5 years.(2) The soil erosion intensity grade was divided into 3 grades including slight, moderate,intensity.The intensity grade included strong and severe grade.The Change trend in slight area was same as the trend in whole basin.The moderate and intensity soil erosion area based on visual interpretation was bigger than RUSLE model respectively. (3) The change trend of annual amount of soil erosion based on RUSLE model and basin export was similar.It changed alternately high and low.The amount of soil erosion of visual interpretation reduced annually.The changed trend of annual rainfall was similar with RUSLE model and basin export,and the changed trend of visual interpretation was similar with sensory evaluation.(4) The annual erosion obtained from RUSLE model of the five years was 1.42,1.05, 1.43,0.95 and 2.47 times than that of visual interpretation.The annual erosion obtained from RUSLE model of the five years was 1.06,1.96,1.53,3.03 and 2.52 than that of conversion basin soil erosion based on basin export observation if the delivery ratio was 0.3.