CULVERT. It is frequently necessary to make a passage for water under roads, railways, banks, canals, etc. The drain made to carry the water in such cases is called a culvert. It may be either flat or arched, and is usually built strongly of masonry or brickwork. The introduction of ferro-concrete affords a ready means of constructing culverts strongly and economically; a con crete arch for such work is sometimes made with reinforcing rods laid in spiral form. The derivation of the word is apparently from Fr. couloir, a water-way.