Dredging is carried out for the following reasons:

Navigation dredging

Navigation dredging: to create or extend harbours, basins, canals, marinas and other facilities. This may be new work – known as capital dredging – or maintenance dredging when it is regularly done to maintain existing waterways.

Construction and reclamation

Construction and reclamation: to provide construction materials like sand, gravel, shell and clay. These materials are used as fill to construct new land areas, such as artificial islands for industrial and residential zones and airports, causeways and highways, as well as for dams, dikes and wildlife habitats.

Beach nourishment

Beach nourishment: to provide fill material to restore beaches that have suffered from erosion. This restoration serves a dual purpose – to improve areas for recreation for residents and tourists, but also to build dunes that protect the hinterland from high tides and floods.

Flood control

Flood control: to improve or maintain the discharge and flow of rivers, channels and other waterways by maintaining, increasing or realigning watercourses or by constructing control structures such as dams, dikes or levees.

Offshore energy

Offshore energy: to level the seabed for underwater foundations upon which oil and gas platforms and monopiles for windmills at sea are placed, as well as laying pipelines, cables and tunnels and backfilling them with rock for stability.

Environmental remediation

Environmental remediation: to remove or remediate underwater pollutants to improve water quality. Remediation dredging can clean-up contaminated waterways as well as settlement or sludge ponds, or mine tailing ponds and rehabilitate contaminated industrial areas, known as ‘brownfields’, which can then be redeveloped.

Mining

Mining: to recover minerals, gems, precious metals and fertilisers, or to remove the overlying material to reach such deposits.

General

General: to maintain irrigation canals and reservoirs and other water infrastructure that are crucial to conserve scarce fresh water supplies.
Given the broad range of types of dredging, no one solution fits all challenges. To ensure the most cost-effective and environmentally sound operations, close cooperation is necessary from the start amongst project owners, contractors and consultants, and stakeholders.