What Is Dredging, and Why Is It Important?

What Is Dredging, and Why Is It Important - Merchant Navy Info - Blog

Dredging involves removing sediment that seeps into the water to clear waterways for ships to pass through. Providing enough space for the construction of important bridges, levees, and dams. And removing silt, noise, and pollutants from the water bed.

What Is Dredging?

It involves the excavation of naturally deposited sediments or man-made debris. Such as stones, sediment, building debris, trash, and animal and plant materials. From the bottom of a shallow marine or freshwater body. It is included. An excavator operator releases it onto the side or bottom of a body of water. The sharp blades of the rotating cutter bar loosen the dirt on the ground, and the submersible pump sucks it up. Ultimately, a treatment vessel or garbage hauler empties the material at the disposal site.

Dredging generally refers to the excavation of sediment collected from the ocean floor and its disposal elsewhere. The oldest known dredging operations are peat excavation and maintenance dredging. Maintenance dredging is a broad term that includes the removal of sediment. And the cleaning, widening, or deepening of a body of water using suction or skimming devices (commonly referred to as dredging).

When Did Dredging Begin?

With the dawn of civilization, goods began to be transported via inland waterways and oceans. However, this transport depended on the capacity of the ship. Which in turn depended greatly on the depth of the water. Siltation, a natural phenomenon in which silt and sediment accumulate on the ocean floor, has always been a threat to shipping, and people have begun to combat the problem of siltation to ensure travel safety.

However, due to a lack of equipment to remove the silt, they began digging it out by hand, which was inefficient and limited to shallow channels. In the 15th century, the increase in maritime trade necessitated the development of bed scrapers, such as the ‘Zeeuwse Krabbelaar,’ a primitive bed leveler.

These floor leveling and scraping devices were used to pick up and dispose of sediment. These dredgers evolved from old factories to modern suction dredgers. Mills, he developed around 1575. It is a type of dredging equipment used to excavate harbors. The watermill had a rotating chain connected to wooden boards, and these wooden boards dug out the mud.

Importance Of the Dredging Process 

Dredging is a very important activity in the maritime industry. This is useful for the following purposes: 

  1. Contributes to safer travel by calming underwater traffic and maintaining proper ground clearance.
  2. Dredging increases the depth of shipping channels, ports, and anchorages, allowing the free flow of maritime traffic.
  3. Dredging is sometimes used to harvest marine resources such as shellfish and mollusks. Therefore, dredging operations will help in studying these great species of marine life.
  4. Dredging is a key requirement to facilitate the construction of networks of bridges, dams, and other civil works in water bodies.

These are just the right dredging tools to remove the required amount of mud in the water of various compositions, allowing civil engineers to achieve superior designs with amazing accuracy.

Different Dredging Methods 

The dredging process combines digging soil beneath the water and removing or extracting that soil from the excavated surface by creating any vacuum or simple suction. Technology that supports the latest excavators. However, the basic method of excavating with an excavator has remained unchanged since the late 19th century. There are three main types of excavators, depending on how debris is removed from the site: 

Mechanical Dredging 

Mechanical dredging uses mechanical tools, such as buckets and grabs, mounted on large barges to collect sediment and place them on a waiting barge until the solids settle. Backhoes and clam dredgers, named after the shovel they use, are the most common types of mechanical excavators that can be used in small areas. Mechanical dredging is usually carried out near the coast. Therefore, mechanical dredging is used to remove onshore or coastal sediments. Dredged sediment is picked up and deposited on nearby land or water or, in most cases, loaded onto another barge designed to transport the sediment. If dredging is done close to an embankment, the sediment can be transferred directly to trucks or rail cars.

Hydraulic Dredging 

During hydraulic dredging, centrifugal pumps remove sediment from the dredging site. Material from the canal floor is sucked into the pipe. Sediment is mixed with water to form a sludge mixture, making it easier to transport by pump. Depending on the pumping distance and a booster pump can be installed to move the sediment through a larger vessel to the nearest shore and maintain a constant production rate. One of the important advantages of the hydraulic dredging method is that sediment can be transported directly to onshore facilities, eliminating the need for other transport media and equipment, and saving additional labour and time.

The Advantages Of the Hydraulic Dredging Method Are: 

  1. Reduced capital costs 
  2. Reduced equipment and transportation usage 
  3. Reduced energy and emissions compared to  mechanical dredging methods 
  4. Safe and efficient 
  5. Hydrodynamic dredging 

Excavator 

Depending on the classification, these can be further classified into different types. Types of Mechanical Excavators These are held in place using anchor piles called spuds.

Bucket Excavator

A  bucket excavator is a stationary excavator that typically uses a winch to rotate in an arc around the excavation site. The waste end is equipped with a bucket to remove sediment and sediment. When turned upside down, the sediment is lowered onto the barge.

Digger: 

This is a stationary excavator with a grab as the digging tool (two equivalent shovels or shells operated hydraulically). Because of its design, it is also known as a clamshell excavator. There are different versions of grippers available for deep-sea processing.

Backhoe Dredger:  

Also known as a fixed-arm dredger, it is a fixed excavator typically mounted on a barge or operating near shore. The dredging equipment is a semi-open shell with a fixed-length hydraulic arm and is used in shallow waters and near ports.

The Main Types Of Hydraulic Excavators Are: 

Suction Shovel: 

A stationary shovel is commonly used in sand mining. It is also the perfect device for removing sludge from sewage treatment plants and other areas where large amounts of sediment need to be removed. The excavator’s suction pipe is inserted into the sand deposit, and a water jet is used to transport the sand upwards from the excavation site. Depending on the location and available transport arrangements, the sediment can be pumped by sucking it into a pipeline, transporting it to a landfill, or loading it onto a barge.

Cutting Head Suction Excavator: 

This is another stationary excavator with a cutting head at the suction end for loosening the ground to be excavated. Similar to a shallow suction dredger, sediment is suctioned and pumped to land or to a barge via a discharge pipeline. Depending on the characteristics of the surface to be dredged, cutting heads can be made of different designs and materials. Helps remove sediment from hard surfaces.

Towing Suction Dredger: 

It is a self-propelled vessel equipped with dredging equipment and a hold or hopper device for filling excavated material during pre-set dredging operations. This type of excavator can open the floor of a ship’s hold and lower the excavated material to a designated location. This dredger is mainly used in open waters such as canals, rivers, and estuaries.

Landfill Dredging: 

This is not the dredging itself but the equipment that assists in dredging operations. It is used to empty the hopper barge of sediment using a suction pipe that can be lowered into the hold of the hopper barge. Additional water can be sprayed to create a sediment slurry to facilitate suction and transport to the desired location or shoreline depot.

Impact of Dredging 

However, just as every coin has two sides, despite all the positives in the process, dredging also has its negative sides. These negative points are also important because they tend to affect the existence and life of marine habitats. The negative effects of dredging are explained below. When dredging is carried out for marine engineering or the construction work,  large quantities of water need to be removed and stored elsewhere. This poses some storage problems but has a major impact on the plant and animal life that inhabits this water. This is because the mineral composition of the water changes before and after dredging and redeposition to the water source after construction.

Dredging operations are used to desilt rivers and have a major impact on local crops, which are primarily used to meet local irrigation needs. Important minerals are dredged along with the mud, so the resulting water and soil are low in nitrates and phosphates. Even if dredging is used for cleanup purposes, removal of toxic waste presents problems for safe disposal. When disposed of on land or in other less important bodies of water to fertilize the soil, it harms the organisms in those bodies of water.

Conclusion 

The excavation industry has developed throughout the world over the past two decades. It serves multiple purposes at the same time, including cleaning, maintenance, disposal, transportation, and excavation. This makes it easier to navigate in the water and makes it easier to fish even in shallow rivers. It helps remove pollutants from waterways and restore damaged areas through restoration efforts. However, one of the important things to keep in mind when dredging is to safely dispose of the removed goods. Please dispose of it in a place that will not cause serious damage to the terrain or living things. Additionally, dredging changes the mineral composition of the water in some areas. Precautions must be taken to monitor changes caused by changes in mineral composition.

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