How are rills and gullies similar?
Runoff begins as sheets of water flowing over than soil surface that soon builds velocity and becomes riverlets that erode small channels (rills 1) that grow in width and depth to become large channels (gullies 1). Water velocity increases with the size of the channel. Water flowing in the largest channels (gullies) has the most erosive power and can carry the heaviest sediment load, while runoff flowing in sheets have the least erosive power and carry the lighest sediment load.
