Spatial and hydrological analysis methods
GIS-based spatial analysis and digital terrain analyses were adopted to explore the spatial distribution of flow path and predicted onsite soil loss rates. The Spatial Analyst Tools distributed with ArcGIS 10.3.1 were used evaluate the effects of roads and other terrain features on flow directions, while the “flowpath” mode in GeoWEPP was used to estimate the erosion rate for each pixel. The ArcGIS hydrological analysis tool was adopted to calculate the upstream flow length for each pixel and delineate sub-catchment boundaries. The ArcGIS Buffer Wizard was applied to generate 10-m-width buffer belts in the downslope direction of the ridge and roads. There are 13 buffer belts below the ridge and 10 belts below each road segment. The WEPP onsite soil loss rate within each buffer belt was extracted to explore the spatial variation in the estimated soil erosion.