Abstract: Topography significantly affects soil erosion, and topographic factors are the key parameters in the water erosion models. Topographic factors in the study of modelling regional soil erosion are mostly extracted from medium and low resolution DEMs, but the extracted slope gradient tends to decrease while the extracted slope length tends to increase, which significantly affect water erosion estimation. This study reviewed the research progresses in the scaling effects of topographic factors and the associated effects on water erosion estimations. Results showed that the scaling effect of topographic factors widely exists in different terrain type areas, but the laws of slope attenuation and slope length expansion are quite different. The scaling effect of topographic factors is related to terrain complexity, and is affected by the terrain information spatial frequency, calculation method and truncation method of topographic factors. The slope gradient and slope length factors in different regions have different sensitivities to DEM resolution, and their effects on water erosion estimation are therefore different. At present, scientists have achieved fruitful results regarding the basic laws of slope gradient attenuation and slope length expansion. However, the mechanism of slope attenuation and slope length expansion, the coupling mechanism of slope and slope length factor scaling effect, the influence mechanism of slope topographic alters caused by human activities on the scaling effects, the regional applicability, geomorphological principles, and uncertainty analysis of topographic factor transformation models need to be strengthened in follow-up research.

Key words: topographic factors, DEM, scaling effects, water erosion estimation, literature review