A culvert is a structure or pipe that allows water to flow underground in order to avoid an obstruction, such as a road or railway. Historically, culverts have even been used to divert watercourses under new housing developments. Culverts can take a number of forms, such as plastic pipes, brick-lined tunnels or concrete structures, and may be used to form a bridge-like structure to carry traffic. Generally, where culverts form part of a watercourse, they will be the responsibility of the Riparian Owner to maintain.