A channel resulting from erosion and caused by the concentrated flow of water during or immediately following heavy rains A gully generally is an obstacle to farm machinery and is too deep to be obliterated by ordinary tillage (A rill is of less depth and can be smoothed by ordinary tillage )
A rift or narrow depression running up cliffs and hillsides In descent, best avoided, unless it is a well-known and easily followed route Often contains running water and loose rock