中文摘要：

地形（LS,slope length factor and slope steepness factor）因子是通用土壤流失方程和修正通用土壤流失方程USLE/RUSLE（universal soil loss equation,revised universal soil loss equation）应用到流域或区域尺度时较难提取的因子。基于坡面水文学和土壤侵蚀学,对流域地形因子的原理、方法、流程进行了讨论。考虑了三维坡面水流发散和汇聚、泥沙沉积、沟道截断等条件,基于GIS技术,提出了基于多流向的地形因子估算方法,设计了LS_TOOL工具。该方法与已有AML（ARC Macro Language）和C＋＋方法计算的坡度坡长结果在空间分布、运行效率等方面进行对比,结果表明：采用多流向方法,计算合理,符合地形因子计算的值域范围;空间结构比AML和C＋＋方法好,与地形相关性较高;效率远高于AML方法,由于增加了沟道提取,其效率稍低于C＋＋方法。该方法可方便的应用于流域和区域尺度下的地形因子估算。

英文摘要：

The universal soil loss equation （USLE） and revised USLE （RUSLE） are often used to estimate soil erosion at regional landscape scales, however the method of extracting the topography （LS） factor is the main limiting factor. The principles, methods, processes for extracting topography factor from watershed scale were discussed based on slope hydrology and soil erosion. With the consideration of the flow divergence and convergence, sedimentation, channels conditions, an estimation method for topography factor was proposed based on multiple flow direction algorithm and GIS. A tool named LS-TOOL was designed for calculating. Comparing with the two methodologies of AML（ARC Macro Language）and C＋＋）, LS_TOOL delivers improved the LS factor. The results showed that results calculated by LS TOOL was more closely with the reality of the Xiannangou catchment than results by AML and C＋＋ in spatial pattern, and LS_TOOL was more efficient than AML and a little bit lower efficient than C＋＋. This research indicated the LS_TOOL can automatically calculate topography factor for watershed and regional scale.