subject: Dredging Basics [print this page] Dredging involves excavating an area that is at least partly submerged. This can involve anything from a river or lake to the open seas. There can be several reasons for dredging an area, but the most common reason is to gather the sediment from the bottom of the lake or section of ocean and then redeposit or dispose of this sediment elsewhere. In many cases, the reasoning behind doing a dredge of an area is to keep the sediment from building up. In some waterways, for example, if too much sediment builds up, larger ships may not be able to use the waterway. In this same way, dredging can also be used to increase a channels or rivers water capacity to help relieve flooding in some areas.
There are some other uses for dredging. Coastal erosion, caused by the waves over times, can leave some public beaches without a good amount of sand. This makes them less attractive to tourists, which in turn means a drop in income for the surrounding area. Dredging up sediment and sand from the bottom can be deposited on the beach to help rebuild the lost sand. Sand gained from dredging can also be used in land reclamation projects and other construction projects.
Another use of Dredging is in fishing. Some edible crabs, clams, and other seafood can be dredged up from the ocean bottom. After the sand is filtered out, these edible fish can be sent to restaurants and food packaging plants for preparation and consumption. Dredging may be used to search through the sediment for other things, including gold, rare minerals, and, in cases of missing people, even bodies.
Dredging is very important in containment of chemical spills, too. In these cases, as much of the contaminated soil is dredged up as possible and then disposed of in some other, safer location. Doing so right away can help protect the local sea life and restore the area to normal quickly. It also prevents chemicals from getting into seafood and local water supplies.
Some environmentalists have suggested the dredging does impact aquatic ecosystems, and they are correct to some extent. Dredging can dislodge chemicals, including heavy metals, in the benthic substrates of the ocean floor, causing these chemicals to enter the water. The turbulence dredging causes, although very short term, can also cause some disturbances in local species migration and metabolism. Theres also a small chance that the sediment taken from the area will contain something that contaminates the site where it is deposited, although samples of the sediment are usually taken and tested before the sediment is deposited.
However, despite the impact dredging can have on the environment, without dredging, much of todays modern commerce would not be as efficient or as effective. Without dredging to clear harbours, channels, and rivers, cargo ships could not access many ports. Recreational boating, too, would be impaired, with all but the smallest ships able to sail on some lakes, rivers, and seas.
by: Chris tyreel
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