The natural sediment found on the bottom of our seas and waterways is constantly on the move, passing silt and debris from one location to the next via tides and currents. This poses a challenge to worldwide ports and waterways, who need to keep a certain depth to allow ships to call safely throughout the year, without touching the bottom in the approach, or at berth. There is a dedicated sector of the maritime industry that ensures that those depths are maintained, known as the dredging sector.
Dredging can be defined as ‘excavation-type’ work, where a dredger removes sediments from an estuary, waterway or ocean floor. This work can include cleaning, deepening, or widening of a body of water using a scoop or suction device. In essence, the dredging process consists of the following three elements: excavation, transport of excavated material and then use or disposal of dredged material.
For shipping, dredging is usually done to increase the depths of channels or ports to improve navigation and increase bottom clearance, but it can also be done to reclaim material for use on land or in port development. Materials normally removed can include rocks, bottom sediments, debris, sand, refuse, and plant or animal matter.
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A dredger is a waterborne vessel equipped with a device or devices for scraping or sucking the seabed. A dredger is designed to remove material, such as sand and gravel, from the bed of the sea or other body of water. In American usage any floating vessel equipped with dredging equipment is called a dredge. The most common types of dredgers are trailing suction hopper dredgers and cutter suction dredgers.