Slough
The Cyclopedic Law Dictionary · Walter A. Shumaker and George Foster Longsdorf; ed. James C. Cahill · 1922
The Cyclopedic Law Dictionary
A swale or slough is a natural depression or natural water course into which surface water may be cast by open or covered drains wholly upon one's own land, without incurring liability to owner of lower land.
157 Iowa 6.