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.