At Marseille, dredging phases are recorded from the third century BC onwards, the most extensive during the first century AD. The seven arms of the Nile were channelled and wharfs built at the time of the pyramids (4000 BC), there was extensive harbour building in the eastern Mediterranean from 1000 BC and the disturbed sediment layers gives evidence of dredging.

History Īncient authors refer to harbour dredging. Disposal can be to infill sites, or the material can be used constructively to replenish eroded sand that has been lost to coastal erosion, or constructively create sea-walls, building land or whole new landforms such as viable islands in coral atolls. The extract can be disposed of locally or transported by barge or in a liquid suspension in pipelines. ĭredging is a four-part process: loosening the material, bringing the material to the surface (together extraction), transportation and disposal. Dredging can be done to recover materials of commercial value these may be high value minerals or sediments such as sand and gravel that are used by the construction industry. It keeps waterways and ports navigable, and assists coastal protection, land reclamation and coastal redevelopment, by gathering up bottom sediments and transporting it elsewhere. These environmental impacts can significantly hurt marine wildlife populations, contaminate sources of drinking water and interrupt economic activities such as fishing.ĭescription Excavator dredger in Neeme harbour, Estonia (April 2023)ĭredging is excavation carried out underwater or partially underwater, in shallow waters or ocean waters. Dredging systems can either be shore-based, brought to a location based on barges, or built into purpose built vessels.ĭredging has significant environmental impacts: it can disturb marine sediments, leading to both short- and long-term water pollution, destroy important seabed ecosystems, and can release legacy human-sourced toxins captured in the sediment. Usually the main objectives of dredging is to recover material of value or use, or to create a greater depth of water. In all but a few situations the excavation is undertaken by a specialist floating plant, known as a dredger. Possible reasons for dredging include improving existing water features reshaping land and water features to alter drainage, navigability, and commercial use constructing dams, dikes, and other controls for streams and shorelines and recovering valuable mineral deposits or marine life having commercial value. For the fishing boat, see fishing trawler.ĭredging is the excavation of material from a water environment.

Sand dredging companies