Culvert
A culvert is a structure that allows water to flow under a road, railroad, trail or similar obstruction. Typically surrounded by soil, culverts may be made from pipe, reinforced concrete or other material.
Illustration: Culvert
Photograph: Culvert
Source: The image above illustrates the key components of Culverts.
A. Headwall: Helps retain the sloping ground above the box culvert or drainage pipes.
B. Flared wings: Helps to retain the sloped ground adjacent to the box culvert or drainage pipe.
C. Gabions, or energy dissipaters: Wire mesh containers filled with rock.
D. Box culvert or drainage pipe: A square or rectangular concrete structure usually made of corrugated metal or concrete.
TxDOT Visual Dictionary