American Oceans

What Is Dredging?

Dredging is the removal of silt from the bottom or banks of rivers, lakes, streams, and other bodies of water. This is done for a variety of reasons.

dredging silt removal in bodies of water

The main goal is to enhance the depth of bodies of water, such as rivers because silt buildup can make it difficult for vessels to navigate through it.

A dredge is a machine that sweeps or suctions silt from the bottom of rivers or is used to mine resources beneath the water’s surface.

While current dredges feature computer-assisted instrumentation, the basic excavation procedures of dredges have remained unchanged since the late 1800s.

dredging machine performing basic excavation procedures

To collect sediment, the dredge is either partially or completely submerged. Traditionally, the dredged or dug-up material is transported to a separate area.

Prior to new environmental guidelines, the recovered dredge was dumped at sea, which can harm marine species such as shellfish.

If the material is free of contamination, it is usually reused; nevertheless, shipping and treating material off-site comes at a considerable expense.

ship using dredging material harmful for the site

And when dredged material is harmful, a genuine concern develops. As a result, treating it on-site may be preferable.

Does dredging kill fish?

Dredging is costly, and according to The Ecosystem Agency, it is damaging to the environment. They believe it can undermine riverbanks as well as bridge and weir foundations.

According to the agency, dredging can also result in the loss of breeding grounds for fish, as well as the extinction of some species and the destruction of the habitat of river bank fauna such as otters and water voles.

Dredging also has a negative influence on crops in areas where it is used to de-silt rivers that are primarily meant to meet the region’s irrigation demand.

Because, in addition to silt, necessary minerals are dredged out, leaving the resulting water and land deficient in nitrates and phosphates.

Also, if dredging is done for cleaning purposes, the toxic material to be removed raises the issue of safe disposal.

If it is disposed of on land, it will render the land barren, and if it is disposed of in a less important water body, it will affect the living animals in that body of water.

What is the purpose of dredging?

Dredging is the process of removing sediment and other items from the bottom of a body of water.

Dredging is required at ports due to the natural building of sand and silt caused by rivers, currents, and streams carrying sand and particles.

Dredges are used in ports all over the world to widen and deepen access levels, assuring safe navigation, gaining a competitive advantage by welcoming huge boats, cleanup, and flood management.

Millions of tonnes of bottom sediments are dredged in our seas and ports each year.

Dredging on a regular basis helps to avoid issues created by the natural process of sand and silt pouring downstream and filling river and sea channels, as well as harbors.

Dredging also facilitates port expansion to handle the growing shipping market: the shipping sector is expanding, and ships are becoming larger. Ports must excavate silt in order to build or expand a port.

Is dredging bad for Rivers?

The capacity of a river is insignificant in comparison to the catchment from which it takes its water.

Dredging can enhance the flow of a river, but this is likely to result in faster and more dangerous floods downstream when the water reaches the nearest metropolitan bridge.

If you cut it off from its floodplain by turning it into a deep trench, you might be able to increase its capacity from 2% to 4% of the water traveling through the catchment.

You will have accomplished nothing while creating a slew of new issues.

Once again, the U.S, Environmental Protection Agency points out that there are several issues with river dredging. Firstly, doing so can be very expensive and usually has to be repeated multiple times.

As well as this, The removal of riverbank vegetation, such as trees and bushes, reduces bank stability and promotes erosion and siltation- making rivers more dangerous.

They also note that If the river channels are dredged but structures are not realigned, ‘Pinch Points’ will form. This would raise the possibility of flooding at the structure. That implies more money and danger.

How does dredging affect climate change?

The usage of fossil-fuel-powered machines and motors is perhaps the most significant contributor to climate change in the present era.

Dredgers are included in this category, and while many organizations have switched to cleaner technologies, many others continue to use these sorts of dredges.

There is a worldwide movement to reduce the quantity of carbon dioxide emitted into the atmosphere as a byproduct of fossil fuel combustion engines. Many dredging businesses are extremely conscious of their fuel use and byproduct creation.

That is why dredging businesses are collaborating with other sectors and fields to reduce the number of fossil fuels they use or to develop technology that will allow them to be completely independent of fossil fuels.

While there is no doubt that gas-powered dredgers have an influence on environmental health, in many circumstances, the job these dredgers conduct has an equally good impact. 

Dredging is widespread around beaches, rivers, ports and harbors, lakes, and ponds. All of these places are being impacted by rising sea levels and increased precipitation levels as a result of more frequent storms.

These storms can cause severe flash floods that can destroy entire villages. Dredges are used to build infrastructure that channels floodwaters away from homes and businesses while also preventing key rivers from flooding.

Dredging is also being implemented in beach restoration projects, environmental cleanup initiatives, and even in the preservation of habitat for native fish and wildlife. 

Dredgers were commonly employed to cut away large swaths of the earth in the past. While they were and continue to be engineering wonders, similar projects today are not environmentally friendly, and for good reason.

Instead, dredging companies are looking more closely at the natural landscape that surrounds each of their worksites to see how they could make use of existing elements to improve the performance of their operations while decreasing the quantity of material they must remove from the site.

How does dredging affect water quality?

Dredging has the greatest impact on estuary water quality because of chemical exchanges between the water and distributed silt.

Estuarine sediments have significant quantities of ammonia when they are first distributed. This boosts microscopic plant production, which leads to increases in pH, dissolved oxygen, and BOD.

In general, the initial impact of dispersing dredged materials is that heavy metals in the water are drained.

However, some metals may be expelled from the sediment over time, increasing the concentration of metals in the water. Dredging operations can spread contaminated materials, exacerbating the pollution problem.

One example is the spread of oxygen-consuming chemicals, nutrients, and hazardous elements clinging to sediments into the water.

This can alter the oxygen level of the sediment or increase the concentration of nutrients or hazardous contaminants.

Dredging has the potential to affect marine animals, however, the impacts vary by species and region, as well as by what dredging equipment is used. 

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