Pipeline dredges use hydraulic dredging to remove sediment in nearshore areas, and the dredged material is discharged through a pipeline leading to a beach or diked area. The ship's hull is filled with dredged material and the ship moves the material to a designated disposal site where it is dumped through doors in the hull. Hopper dredges are vessels that employ hydraulic dredging, and they are often used in the open ocean or in areas where there is vessel traffic.

Most of the dredging that occurs in the United States is hydraulic dredging. It lifts sediment from the bottom by metal clamshells or buckets without adding significant amounts of water, and the dredged material is usually transferred to a barge for disposal at a particular site. Mechanical dredging is typically used to dredge small amounts of material. Hydraulic dredging involves suspending the sediment, which mixes with water to form a slurry, and pumping it to a discharge site. Technology currently used to dredge sediment from a harbor, bay, or other marine bottom consists of hydraulic or mechanical devices. An object is dragged along the bottom with the prevailing current this suspends the sediment and the current carries the suspended material away from the area. One of the oldest types of dredging is agitation dredging, which uses a combination of mechanical and hydraulic processes and dates back over 2,000 years. Hundreds of millions of cubic feet of sediment are dredged from marine bottoms annually in the United States and throughout the world. Dredging is also used to collect sediment (usually sand and gravel) for construction and other commercial uses. If dredging were not done, harbors would eventually fill in and marine transportation would be severely limited.

Maintenance dredging is required because sediment suspended in the water eventually settles out, gradually accumulating on the bottom. Dredging sediment to construct new ports and navigational waterways or maintain existing ones is essential for vessels to be able to enter shallow areas. Dredging is a process to remove sediment.

What is a dredge