This study took Shangnan County

located in the upper reach of the Yangtze River

as the experimental research area

using Quantitative Remote Sensing Model（QRSM. Digital elevation model (DEM) of the research area was constructed with a GIS software platform

with the gradient and slope length factor (SL) derived based on the soil erosion factor algorithm-specific software. The factors influencing the generation of the high precision digital elevation model (DEM) were analyzed. The accuracy and error of the produced DEM were also checked. In particular

the solutions to the derivation of the terrain pixel factor SL of water boundary slope

slope factor

slope length

slope length factor and concave point problem and reflux technology processing were developed. The results indicated that

in Shangnan County

the slope area located on the 15° to 25° degrees was 530.51 km2

accounting for 22.93% of the total area. The slope area on the 25° to 45° degrees was 1 083.32 km2

accounting for 46.82% of the total area. The slope area on the 15° to 45° degrees accounted for 70% of the total area. This area was the main cause driving the serious soil erosion in Shangnan County

this results of this study were consistent with the actual status of the study area. This research extended the application of the QRSM to the upper reaches of the Yangtze River

being meaningful for further monitoring and forecasting of soil erosion across the whole of the Yangtze River Basin. Our study is also valuable for soil erosion monitoring in other small catchments

both theoretically and practically.