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What is Dredging?

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  • Written By: J.Gunsch
  • Edited By: Lucy Oppenheimer
  • Last Modified Date: 11 September 2016
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Dredging is a process that involves the aquatic excavation of water beds to remove sediments, pollutants, shellfish and other materials. The methods and machinery used in dredging vary widely. Most dredging is done by ships that tow a dredge along the water bed. Self standing dredges and dredge pumping stations are used for routine tasks. A dredge, which is the catch all term for the different types of machinery that perform dredging, can cut away sediment, scoop materials out like a back hoe or suction them through a large pipe to be deposited into a ship, barge or other containment system.

Dredging serves four general purposes:

1) Dredging is preformed to create or deepen waterways to allow large ships to pass. Throughout time, waterways become filled with silt and sediment which require fairly general maintenance in order to be efficient. With ever expanding markets, there is also a demand for the creation of new waterways.

2) Dredging is used to catch seafood. This type of dredging involves dragging a metal mesh net along the bottom of the ocean floor or other large body of water to catch animals such as crabs, fish and squid.

3) Dredging is performed in the attempt to remove pollutants and invasive species of plants from a particular body of water, although this practice is controversial. Removing pollutants this way often causes other environmental problems such as the destruction of habitats of important plant and animal species.

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4) Dredging can be used to remove desired materials from the waterbed such as minerals. It can also be used for land restoration by dumping dredged sediments onto land that has been lost to the sea as in the case of the gulf coast in the United States. Similarly, some beaches are maintained this way by collecting offshore sand and redistributing it along the beach.

Dredging poses many environmental problems. There is the issue of where the dredged material will be disposed. Often the material is dumped in estuaries, which are shallow inlets of a sea or a river mouth. Dumping in estuaries can result in flooding and the destruction of rich habitats. In the United States, laws have been developed under the Clean Water Act to keep dredging activities in check and to minimize environmental consequences. As the environmental effects become more obvious, the dredging industry is working to improve machinery and dredging processes using alternative methods when possible.

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shell4life
Post 5

I know that sand dredging can sometimes be a good thing, because it provides material that can be used to restore and protect beaches. I vacation on the Gulf coast every year, and the beaches there have to be restocked with sand that has been gathered by dredging.

The waves cause so much erosion, and since hotels and condos line these beaches, they have to be preserved, or millions of dollars will be lost. This is a good place for dredgers to dump their extra sediment.

The only issue I have heard people complain about is the protection of sea turtles. They bury their eggs in sand, so when extra sand is dumped on top, the baby turtles may be in too deep to ever dig their way out.

seag47
Post 4

@Perdido – I don't like to think about dredging in that aspect. I always think of crab fishermen when I think of dredging, because my brother-in-law is a commercial crab fisherman.

He told me that they use a net of metal and twine to get the crabs. In the winter, some crabs go into hibernation in the sand on the ocean floor. The dredge has teeth that scour the bottom and disturb the sand, making the crabs float up and get caught in the net of chain.

It must be a cruel awakening. I would hate to be disturbed from a deep sleep only to find myself caught in a net.

Oceana
Post 3

My neighbor hired a dredging company to improve the appearance of the pond in her yard. It had become inundated with green algae, and it looked disgusting. The pond's purpose was to beautify her yard, and it had become an eyesore.

The dredging company used a hose to pump the sludge out of her pond. I'm not sure where they deposited it, but they sucked all the nasty stuff out into a big container and drove away with it.

The results amazed me. They got rid of that layer of bright green film on the top, but they also got rid of whatever was on the bottom, because I could see clearly all the way down after things had settled back out.

Perdido
Post 2

I always wonder when I see lake dredging in progress whether the workers are getting rid of sediment or looking for a dead body. I have heard the term “dredging” in reference to looking for a drowning victim who has sunk many times, so I always associate the word with a negative thing.

Generally, bodies will float to the surface. However, some murderers decide to anchor bodies down with concrete, and this is where dredging comes in handy.

If I see cop cars and investigators standing on the shore while dredging is going on, then I automatically think the worst. If no officers are present, though, then the lake is probably just being dredged of sediment.

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