Difference Analysis Of LS Factor Algorithms In The Typical Geomorphologic Areas Of Loess Plateau

Aiming to investigate the overall variation characteristics of LS factor and soil erosion of difference methods to calculate LS of gullies different in geomorphic type and resolution,typical gullies were picked out in loess tableland、Loess ridge and loess hill,the results of the paper are summarized as follows:The LS factor value obtained by liu bao-yuan algorithm from high to low is: the gully developed on Loess ridge,the gully developed on loess tableland,the gully developed on loess hill,the LS factor value obtained by Moore and Desmet algorithm from high to low is: the gully developed on loess tableland,the gully developed on Loess ridge,the gully developed on loess hill.Whatever algorithm we use,the LS factor value of loess hill is always the lowest,However,the LS factor value of loess tableland and Loess ridge will change with the different of calculation method,In liu bao-yuan algorithm,In addition to the slope factor,the slope length factor is also considered,so the amount of erosion of Loess ridge is greater than that of loess tableland,In Moore and Desmet algorithm,besides the slope factor,the unit catchment area and catchment area are mainly considered rather than Slope length,so the amount of erosion of loess tableland is greater than that of Loess ridge.Compared with the existing research,the results of liu bao-yuan algorithm are basically same,the Moore algorithm are inconsistent because the maximum and minimum values of LS factor are far from 37.3% of the existing research in 10~20 range,the percentage of area in the Desmet algorithm is lower than the existing study,which is quite different from that.The reason may be that Moore and Desmet algorithm are summarized based on a large number of experiments abroad,although the formula is universal,it is not applicable to some special topography.When it is used to calculate the LS factor of loess plateau in China,the difference of district is unavoidable,so it is better to make appropriate conversion to the parameters.When the grid size increases,in liu bao-yuan,Moore and Desmet algorithm,the area proportion of LS factor in low rang increases as well,while the proportion of LS factor in high rang is decreased,the proportion of LS factor in the intermediate rang is not very variable.The reason is that When the grid size increases,each grid accommodates more terrain information,Some local topographic features are easily integrated and simplified,so terrain becomes more smooth,the area proportion of LS factor in low rang increases,Accordingly,the proportion of LS factor in high rang is decreased.With the reduction of resolution,the maximum amount of loss of area percentage of LS factor grades in liu bao-yuan algorithm appears in 0~5 range,in Moore and Desmet algorithm appears in 5~10 range and greater than 20 range,and the magnitude of loss in Desmet algorithm is More serious than Moore algorithm.It means that the range sensitized to resolution in liu bao-yuan algorithm appears in low rang,in Moore and Desmet algorithm appears in high rang,and Desmet algorithm is more sensitive than Moore,Similarly,the error of algorithm from high to low is : Desmet,Moore,liu bao-yuan.In general,when calculating the LS factor of loess plateau,the most suitable one is liu bao-yuan algorithm,followed by Moore algorithm,and finally the Desmet algorithm.