Sill

Structure located in the minor bed of a watercourse to fill an excessive bed depression caused by the extraction of materials or by a structure for example. It can be a low structure normally submerged, built for various purposes, possibly to stabilize the water level/flow rate ratio in a stream at a station, or the top of a dike or of any other structure, or of a natural levee, on which water can flow when it reaches a sufficient level.