Abstract:

Topography significantly affects soil erosion, and topographic factors are key parameters in water erosion models. Topographic factors in existing modelling of regional soil erosion are mostly extracted from medium and low resolution DEMs,resulting in under-estimated slope gradient and over-estimated slope length,significantly affecting water erosion estimations. This study reviews 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. These scaling effects are influenced by terrain complexity,spatial frequency of terrain information,calculation methods,and truncation techniques. The sensitivity of slope gradient and slope length factors to digital elevation model(DEM) resolution varies by region,leading to differential impacts on water erosion estimations. While scientists have made considerable achievements in elucidating the fundamental laws of slope gradient attenuation and slope length expansion,several critical areas need to be further explored,including the mechanisms underlying slope gradient attenuation and slope length expansion,the coupling mechanisms of slope gradient and slope length factor scaling effects,the impact of topographic alterations caused by human activities on scaling effects,the regional applicability,geomorphological principles,and the uncertainty analysis of topographic factor transformation models.

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