a structure or excavation at the foot of a chute, drop, or spillway to reduce open the energy of the descending runoff or stream

A stilling basin is a basin constructed to dissipate the energy of fast flowing water. The stilling basin area is located just downstream of the spillway crest between the training/retaining walls.

A basin downstream from a dam that receives the discharge from tunnels or conduits or overflow from a spillway.

An area ahead of the weir plate large enough to pond the liquid so that it approaches the weir plate at low velocity, also called "weir pond."

An enlarged area in a channel that is deep enough to reduce flow velocity.