Scaling Effects And Re-scaling Of Slope Length And Steepness Factor(LS)

Slope length and steepness factor(LS)is an important terrain factor that affects regional soil erosion.In regional soil erosion evaluation mapping,the LS factor is generally extracted and calculated by coarse resolution DEM.With the decrease of DEM resolution,the phenomenon of slope attenuation and slope length expansion occurs,which makes the LS factor cannot accurately express the relationship between terrain and soil erosion.Understanding the relationship between DEM resolution and LS is an urgent problem to be solved in regional soil erosion assessment.This paper analyzes the scale effects and main control factors of LS factors in different terrains around the world with different resolution data,and downscales the coarser resolution data to evaluate its effect.The main conclusions are as follows:(1)With the decrease of the DEM resolution,the LS value shows a downward trend in micro-undulation,small relief and medium relief region,and the spatial distribution mainly changes as the range of obstacle values decreases;in large and medium relief,large relief,and extremely large relief region,the LS value showed an upward trend,and the main change in the spatial distribution was an increase in the larger value range.(2)With the decrease of DEM resolution,the rate of slope decrease is less than the rate of increase of slope length;in micro-undulation,small relief and medium relief region,the decrease rate of S factor is greater than the increase rate of L factor,namely the slope steepness factor(S)is the main control factor;in large and medium relief,large relief,and extremely large relief region,the decrease rate of S factor is less than the increase rate of L factor,that is,the slope length factor(L)is the main control factor of LS scaling effects.(3)The LS factor after downscaling is more similar to the high-score data in the macroscopic spatial pattern,and is more similar to the 30 m resolution(before downscaling)data in the image texture(the ability to express terrain features such as channels),that is,the spatial frequency loss caused by the decrease of DEM resolution is not recovered.In the geomorphic area(except for micro-undulations).The average value of the LS factor after downscaling is close to the high score data,and the histogram intersection area of the highresolution and down-scaled data is greater than the histogram intersection area of the high-score and coarse-resolution data.The result shows that the downscaling effect is better.