Columbia subject headings:
Erosion.
Geomorphology--Arid regions.
Hydrology.
Slopes (Physical geography)
Harvard subject headings:
Geomorphology.
Landforms.
Soil erosion.
Soil piping (Hydrology)
Subsurface drainage.
Princeton subject headings:
Erosion.
Geomorphology--Arid regions.
Hydrology.
Slopes (Physical geography)