Editing Dredging (section)

==Purposes==
*'''Capital dredging''': dredging carried out to create a new [[harbour]], [[Berth (moorings)|berth]] or [[waterway]], or to deepen existing facilities in order to allow larger ships access. Because capital works usually involve hard material or high-volume works, the work is usually done using a cutter suction dredge or large trailing suction hopper dredge; but for rock works, drilling and blasting along with mechanical excavation may be used.
*'''[[Land reclamation]]''': dredging to mine sand, clay or rock from the seabed and using it to construct new land elsewhere. This is typically performed by a cutter-suction dredge or trailing suction hopper dredge. The material may also be used for [[flood]] or [[erosion]] control.
*'''Maintenance''': dredging to deepen or maintain navigable [[waterway]]s or [[Channel (geography)|channels]] which are threatened to become silted with the passage of time, due to [[sediment]]ed sand and mud, possibly making them too shallow for navigation. This is often carried out with a trailing suction hopper dredge. Most dredging is for this purpose, and it may also be done to maintain the holding capacity of [[reservoir]]s or lakes.
*'''Harvesting materials''': dredging [[sediment]] for elements like [[gold]], [[diamond]]s or other valuable trace substances. Hobbyists examine their dredged matter to pick out items of potential value, similar to the [[Coin shooting|hobby of metal detecting]].
*'''[[Fishing dredger|Fishing dredging]]''' is a technique for catching certain species of edible [[clam]]s and [[crab]]s. In Louisiana and other American states, with salt water estuaries that can sustain bottom [[oyster bed]]s, oysters are raised and harvested. A heavy rectangular metal scoop is towed astern of a moving boat with a chain bridle attached to a cable. This drags along the bottom scooping up oysters. It is periodically winched aboard and the catch is sorted and bagged for shipment.<ref name="reasons" />
* '''Preparatory''': dredging work and excavation for future [[bridge]]s, [[pier]]s or [[Dock (maritime)|docks]] or [[Wharf|wharves]], This is often to build the [[Foundation (architecture)|foundations]].
* '''Winning construction materials''': dredging sand and gravels from offshore licensed areas for use in construction industry, principally for use in concrete. This very specialist industry is focused in NW Europe, it uses specialized trailing suction hopper dredgers self discharging the dry cargo ashore. Land based old river beddings can be processed in this manner too.
* '''[[Soil contamination|Contaminant]] [[Environmental remediation|remediation]]''': to reclaim areas affected by chemical spills, storm water surges (with [[urban runoff]]), and other soil contaminations, including silt from [[sewage sludge]] and from decayed matter, like wilted plants. Disposal becomes a proportionally large factor in these operations.
* '''[[Flood prevention]]''': dredging increases the channel depth and therefore increase a channel's capacity for carrying water.

===Other===

* '''[[Beach nourishment]]''': this is mining sand offshore and placing on a beach to replace sand eroded by storms or wave action. This enhances the recreational and protective function of the beach, which are also eroded by human activity. This is typically performed by a cutter-suction dredge or trailing suction hopper dredge. <ref>{{Cite journal |last1=Davison |first1=A. Todd |last2=Nicholls |first2=Robert J. |last3=Leatherman |first3=Stephen P. |date=1992 |title=Beach Nourishment as a Coastal Management Tool: An Annotated Bibliography on Developments Associated with the Artificial Nourishment of Beaches |url=https://www.jstor.org/stable/4298052 |journal=Journal of Coastal Research |volume=8 |issue=4 |pages=984–1022 |jstor=4298052 |issn=0749-0208}}</ref>
* '''[[Peat extraction]]''': ''dredging poles'' or ''dredge hauls'' were used on the back of small boats to manually dredge the beds of [[peat]]-[[Moorland#Heather moorland|moor]] waterways. The extracted peat was used as a fuel. This tradition is now more or less obsolete. The tools are now significantly changed.<ref>{{Cite web |title=Dredge-pump Ship deepen the Estuary of the River Venta - redzet.eu |url=https://www.redzet.eu/en/photo/dredge-pump-ship-deepen-the-estuary-of-the-river-venta-V-025-11 |access-date=2022-07-04 |website=www.redzet.eu}}</ref>
* '''Removing rubbish and debris''': often done in combination with maintenance dredging, this process removes non-natural matter from the bottoms of rivers and canals and harbours. {{anchor|Police drag}}Law enforcement agencies sometimes need to use a 'drag' to recover evidence or corpses from beneath the water.
* '''[[eutrophication|Anti-eutrophication]]''': A kind of contaminant remediation, dredging is an expensive option for the remediation of eutrophied (or de-oxygenated) water bodies; one of the causes is like mentioned above, [[sewage sludge]]. However, as artificially elevated phosphorus levels in the sediment aggravate the eutrophication process, controlled sediment removal is occasionally the only option for the reclamation of still waters.{{citation needed|date=July 2018}}
* '''[[Deep sea mining|Seabed mining]]''': is a possible future use, recovering natural metal [[ore]] nodules from the sea's [[abyssal plain|deepest troughs]].<ref name="reasons">{{cite web |title=EuDA - About dredging - Dredging - Reasons for Dredging |url=https://www.european-dredging.eu/Reasons_for_Dredging |website=www.european-dredging.eu |access-date=3 July 2018 |language=en}}</ref>