Dredging
Dredging is the excavation and removal of sediment and material from the bottom of channels, berths and harbours to create or maintain sufficient water depth for ships. It divides into capital dredging — deepening or widening to a new depth, for example to accommodate larger vessels — and maintenance dredging, the ongoing removal of silt that naturally accumulates and would otherwise reduce depth.
Because ever-larger ships need deeper water, dredging is central to a port's ability to stay competitive and handle modern tonnage — an under-dredged channel restricts the draft, and therefore the cargo, of ships that can call. Dredging is carried out by specialised vessels and is subject to significant environmental regulation, since it disturbs the seabed and must manage the disposal of dredged material and effects on water quality and marine life. Depth, and the dredging that sustains it, is a fundamental constraint on port capacity.
Ports live and die by their depth — as ships grow, a channel that isn't dredged deeper limits the cargo vessels can bring, and silt constantly threatens to shallow it. Dredging is the costly, environmentally sensitive work that keeps a port able to take modern ships. It is a fundamental, ongoing constraint on port competitiveness.
What is the difference between capital and maintenance dredging?
Capital dredging deepens or widens to a new depth; maintenance dredging removes accumulating silt to preserve existing depth.
Why do ports dredge?
To provide and maintain the water depth that larger ships need, since insufficient depth limits vessel draft and cargo.