آب‌باریکه

thumb|right|A downslope view of part of the erosion|eroding rill network from [[County Tyrone, Northern Ireland. See below for a close-up view of a single rill]] In hillslope geomorphology, a rill is a shallow channel (no more than a few inches/centimeters deep) cut into soil by the erosive action of flowing surface water. Similar but smaller incised channels are known as microrills; larger incised channels are known as gullies.