2.4 Extraction of morphological features of gullies
The gully recognition and DEM data were imported into ArcGIS software to extract the morphological features of gullies (e.g., number, length, width, area, frequency, density, and dissection degree) using Spatial Analyst and 3D Analyst tools. The attribute calculation function is used to obtain the projected gully length, which is divided by the cosine value of the corresponding slope to obtain the gully length. The distance measurement function is used to calculate gully width from the horizontal distance of five equally spaced sections. The gully area is the gully width multiplied by the corresponding gully length. Gully frequency is the number of gullies per unit area of the watershed, reflecting the erosion intensity of gullies in the watershed. Gully density is the total length of gullies per unit area of the watershed, reflecting the length characteristics of gullies in the watershed and the degree of surface fragmentation. The dissection degree of gullies is the total area of gullies per unit area of the watershed, reflecting gully development in the watershed.