Dredging facts for kids

A grab dredge

Dredging is like a big underwater digging project! It's when special machines dig up material from the bottom of a lake, river, or ocean. Sometimes, they even dig in areas that are temporarily filled with water.

People do dredging for many reasons. It can help make waterways better, change the shape of land and water, or build things like dams and dikes. Sometimes, they even dig to find valuable minerals or sea creatures.

Most of the time, this digging is done by a special floating machine called a dredger.

Dredging happens in many places and for different goals. But the main reasons are usually to find useful materials or to make the water deeper.

Dredgers are generally sorted into two main types: suction dredgers and mechanical dredgers.

What is Dredging For?

Dredging is a very important activity that helps us manage our water environments. Here are some of the main reasons why people dredge:

• Making Waterways Deeper: One common reason is to make rivers, harbors, and canals deep enough for large ships to pass through safely. This is super important for trade and travel.
• Creating New Land: Sometimes, the material dug up from the water is used to create new land areas. This can be for building, farming, or even creating new islands.
• Protecting Coasts: Dredging can help move sand to beaches that are eroding (wearing away). This protects coastal areas from storms and helps keep beaches nice for people to enjoy.
• Finding Valuable Materials: Dredgers can also be used to find and collect valuable things like sand, gravel, gold, or other minerals from the seabed.
• Cleaning Up Waterways: In some cases, dredging helps remove pollution or unwanted mud from the bottom of rivers and lakes, making the water cleaner and healthier.

How Do Dredgers Work?

Dredgers are special boats or machines designed to dig underwater. They use different methods to scoop up or suck up material from the bottom.

Suction Dredgers

Suction dredgers work a bit like a giant vacuum cleaner. They use powerful pumps to suck up a mixture of water and material (like sand, mud, or gravel) from the seabed.

• Trailing Suction Hopper Dredgers: These are large ships that sail slowly, dragging a long pipe along the seabed. The pipe sucks up material, which is then stored in a large hold (called a hopper) inside the ship. Once full, the ship sails to a different location to unload the material.
• Cutter Suction Dredgers: These dredgers have a rotating cutter head at the end of a ladder. The cutter head breaks up hard material like clay or rock, and then a powerful pump sucks the loosened material through a pipeline. This material is often pumped directly to a nearby land area or another barge.

Mechanical Dredgers

Mechanical dredgers use physical tools like buckets or grabs to scoop up material.

• Grab Dredgers: These dredgers have a large clam-shell-shaped bucket that opens and closes to grab material from the bottom. They lift the material and then drop it into a barge or onto the shore.
• Bucket Dredgers: These are older types of dredgers that use a continuous chain of buckets to scoop up material. As the chain rotates, each bucket digs into the seabed, lifts the material, and then empties it into a chute.
• Backhoe Dredgers: These are like giant excavators mounted on a barge. They have a large digging arm with a bucket that scoops material from the bottom, similar to how an excavator works on land.

Images for kids

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  Reconstruction of the mud-drag by Leonardo da Vinci (Manuscript E, folio 75 v.)

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  Reconstruction of the mud-drag

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  The dredge drag head of a suction dredge barge on the Vistula River in Warsaw, Poland

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  The Geopotes 14 lifting its boom on a canal in The Netherlands. (gēopotēs is Greek for "that which drinks earth")

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  Bucket dredging

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  Old Dutch bucket dredging vessel Hollandsch Diep 4

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  Mallard II near the Dumbarton Bridge in 2021

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  French hopper dredger Daniel Laval at work on the Seine estuary (2018)

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  Grab (clamshell) dredge Njord of the Manson Construction Co. fleet in the Port of Oakland, California

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  The excavator of a Yukon dredge.

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  April Hamer at Lakes Entrance, Victoria Australia

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  The Orisant a trailing suction dredger in the port of IJmuiden, Netherlands

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  Grab dredging in Victoria Harbour, Hong Kong

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  Alexander von Humboldt of the Jan De Nul fleet

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  Sand mining

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  HR Morris of the Manson Construction Co. fleet, a Cutter Suction Pipeline Dredge, working on Mission Bay, San Diego, California

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  Dredge ship with barges on Neva bay in Saint Petersburg, Russia

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  Top view of a suction dredger on the Nandu River, Hainan, China

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  Cutterhead of dredge Bill Holman, Louisville, Kentucky, USA, Ohio River mile 607, July 2002

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  Xcentric Ripper XR120 is a large jackup leg backhoe dredger

See also

In Spanish: Dragado para niños