A marine vessel fitted with a device(s) to scrap or suck the sediment deposition over sea bed is known as a dredger (The device used for excavation and scraping of the sea bed is called the Dredge).

In a more general sense, a ship equipped with excavation tool which is capable of weeding off depositions such as sand, gravel, sediments, etc. from the seabed is referred as dredger ship or more commonly a dredger.

Dredgers are of great importance, as they serve the purpose of ensuring the necessary safe bottom clearance for the safer voyages.

The excavation carried out in either shallow or fresh waters with the aim to gather up the sediments located in the bottom to dispose off at another place is called Dredging.

The sediments might be gathered for purposes like:

  • making the water navigation or fishing easier in shallow waters
  • for replenishing the sand on public beaches which might have undergone severe coastal erosion
  • Gold and coal mining
  • Removal of contaminants from the sea bed
  • Reclamation of areas damaged by oil spills or natural calamities
  • Creation of new harbours

Broadly the types of dredgers are classified into three categories (On the basis of the method employed for transportation, of dredged material from the bottom of the sea to the surface of the water):

  • Mechanical dredgers which are suited for working in confined areas and are useful for removing the hand-packed material or debris,
      (i) Bucket Dredgers
      (ii) Bucket Ladder Dredgers
      (iii) Grab Dredgers
      (iv) Backhoe Dredgers
  • Hydraulic dredgers which work on the principle of adding large amounts of process water to change the original structure of the sediments,
      (i) Suction Dredgers
      (ii) Trailing Suction Hopper Dredger
      (iii) Water Injection Dredger
  • Other dredgers which do not fit into the above two categories.
      (i) Jet-lift dredgers and Air-lift dredgers
      (ii) Augur suction dredgers
      (iii) Reclamation Dredger
      (iv) Pneumatic dredgers
      (v) Amphibious dredgers
      (vi) Plough or bed leveler