Water Drop

(or overfall), in hydraulic engineering, a water-conveying structure in a conduit, floodgates, or other waterline; the structure is designed to unite two sections situated at different levels when there is a marked change in the longitudinal profile of the course. With respect to their structure, water drops are classified as step-type (the most common), in which the reaches of a channel are joined by vertical walls and horizontal areas, or steps; overhang-type; tubular-type; shaft-type; inclined-type; and combination-type. According to the nature of the water motion in them, they are classed as open, semipressurized, and pressurized. Water drops are constructed of concrete, reinforced concrete, stone, brick, metal, or wood.