what is culvert

A culvert is a structure that channels water past an obstacle or to a subterranean waterway. It is typically embedded so as to be surrounded by soil and may be made from a pipe, reinforced concrete, or other materials. Culverts are commonly used both as cross-drains to relieve drainage of ditches at the roadside and to pass water under a road at natural drainage and stream crossings. They come in many sizes and shapes, including round, elliptical, flat-bottomed, open-bottomed, pear-shaped, and box-like constructions. The type and shape of culvert selected depend on factors such as requirements for hydraulic performance, limitations on upstream water surface elevation, and roadway embankment height. Culverts may also be bridge-like structures designed to allow vehicle or pedestrian traffic to cross over the waterway while allowing adequate passage for the water. The common types of culverts include pipe culvert, box culvert, arch culvert, bridge culvert, and metal box culvert. The design of culverts is based on hydraulic, water surface elevation, roadway height, and other conditions. Culverts help prevent roadway or railway flooding and protect cables that run from one side of a roadway or railroad to another.