<Dd> For suction - type excavation out of water, see Suction excavator . </Dd> <P> These operate by sucking through a long tube, like some vacuum cleaners but on a larger scale . </P> <P> A plain suction dredger has no tool at the end of the suction pipe to disturb the material . This is often the most commonly used form of dredging . </P> <P> A trailing suction hopper dredger (TSHD) trails its suction pipe when working . The pipe, which is fitted with a dredge drag head, loads the dredge spoil into one or more hoppers in the vessel . When the hoppers are full, the TSHD sails to a disposal area and either dumps the material through doors in the hull or pumps the material out of the hoppers . Some dredges also self - offload using drag buckets and conveyors . </P>

When water and sediment are emptied out into the river what is this known as