Usually metal or plastic pipe but can be a constructed wooden trough.

Underground pipes designed to carry water, both from creeks and/or as part of a flood control or storm sewer system. Apart from the aesthetic and ecological losses of culverting open creeks, culverts create as many problems (or more) than they "solve." Problems include: back-up of flood flows (culverts can only carry a finite amount of water, unlike natural streams which will overflow higher up their banks), leading to flooding of streets, homes, etc.; increasing water pressure and velocity by constraining the water to a small diameter, thereby causing erosion and water quality problems downstream, and preventing fish from migrating upstream; and failure and collapse of the culverts themselves - which will always happen over time - which places overlying structures and downstream areas at high hazard risk.