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How is dredging a river done?

Dredging is an essential maintenance process within rivers that is used to manage the build-up of sediment, and with so many rivers throughout the UK water network, dredging is the method used to maintain navigability, improve water flow, and minimise the risk of flooding. In our latest blog post, we take a closer look at the process of river dredging and the benefits.

What is dredging?

Dredging requires the use of specialised equipment that is designed to remove sediment, debris and material build-up from rivers, channels, streams, and canals. The process involves the excavation, removal, and transportation of sediment build-up to ensure the depth and capacity of the important waterways is maintained. There are also times when the depth and width of waterways needs to be increased to allow for larger vessels or increased traffic, and dredging is the process which achieves this.

How are rivers dredged?

1. Surveying and planning

At the start of every dredging project a detailed survey is completed to allow engineers to assess the sediment accumulation, environmental impacts, and the conditions within the riverbed and surrounding banks. Specialist equipment is used to gather data such as water flow rates, flood zones, sediment analysis, water quality, fish populations and potential protected species, with the results used to create an effective dredging plan.

2. Dredging techniques

  • Dredging pumps and suction pipes – This is a method for removing materials from riverbeds, with materials transported via barges to disposal sites. For large scale projects, hydraulic jets are often used alongside suction hopper dredgers. This method tends to cause major disruption to the riverbed, and while it is popular with those searching for key materials, it isn’t a technique used by The Rothen Group.

  • Mechanical dredging – A combination of long reach excavators, crane boats and floating dredgers featuring cutter heads are used to physically remove sediment from canals and rivers. These mechanical techniques are ideal for deeper channels and awkward sites, especially as long reach excavators can reach up to 70m, and here at The Rothen Group we are pleased to offer a wide variety of mechanical machinery.

  • Drilling and blasting – Although not a common technique within UK waterways due to the soft sediment types, there are situations where these methods are used to remove rock or particularly hard sediments.

3. Disposing of sediment

There are many situations where the removed sediment can be used within new projects, such as the creation of wildlife habitats, land reclamation and to replenish marshes, beaches, and dunes. If this is not possible, sediment is transported to approved disposal sites in accordance with environmental guidelines.

Does dredging a river reduce the risk of flooding?

Yes, dredging is a method used to reduce the risk of flooding which is a significant risk in many areas of the UK. However, the effectiveness will depend on several factors, including:

  • Increasing the capacity of the waterway – When sediment is removed from the waterway the depth and width naturally increases, which allows the channel to carry more water during period of heavy rainfall, therefore reducing the risk of flooding.

  • Improved channel flow – By removing the debris and sediment which creates blockages the flow of the water improves, which allows water to drain into the necessary catchment areas to prevent flooding.

  • Targeted flood risk reduction – There are situations where localised dredging is used to reduce flood risks, such as natural constrictions and bends. By removing the deposits which reduce the channel size, the overall risk reduces, and floodplain management is more effective.

While the above benefits clearly help to alleviate flood risks, there are additional techniques and solutions which need to be implemented to create an efficient flood prevention strategy. With the impacts of rainfall, topography, land use and river basin management all impacting the risk of flooding, an effective strategy needs to be created which includes everything from dredging and drainage through to floodplain zoning and forecasting.

How does dredging impact rivers?

Although dredging is an excellent way to improve waterway navigation and reduce the risk of flooding, there are some impacts on the overall ecosystem which need to be considered during every project. Throughout the UK, environmental regulations and guidelines are in place to ensure dredging projects are completed in a sustainable way.

This is why it is so important to hire a professional team such as The Rothen Group, as we can work closely with bodies such as the Environmental Agency to ensure proposals and works completed are fully compliant with the relevant environmental standards.

  • Disruption of sediment – Removal of sediment can disrupt the aquatic ecosystem and the overall stability of the banks. The Rothen Group engineers always consider these risks and within every project our team work hard to maintain the ecological systems which support the diverse habitats, and we take steps to ensure excess sediment is not removed or disrupted.

  • Water quality – Although temporary, the disturbance of sediment within the waterway can reduce the water quality as fine particles are resuspended within the channel. These will settle and our team plan dredging projects to ensure disruption is minimised and localised, which helps to improve sunlight penetration and oxygen levels.

  • Removal of habitats – There are many protected species which use the UK waterways as spawning grounds and habitats, which could be impacted by the removal of flora and flora within waterway ecosystems. We work hard to complete detailed environmental assessments and continually monitor ecological disturbances during projects to ensure that our dredging strategy minimises potential habitat risks.

As a team, our engineers and operators have extensive experience in liaising with agencies, environmental experts, and the local communities. This allows us to create dredging project plans which strike the careful balance required between maintaining and improving navigability, reducing flood risks, and protecting the waterway ecosystems.

The Rothen Group – An experienced dredging team that deliver exceptional results

As a company, we have the in-house experience, expertise and machinery required to complete dredging projects of every scale, and we are proud of our commitment to approaching every project with precision and care. To discuss your dredging requirements in more detail, please contact our team and together we can create a plan which preserves the efficiency and resilience of the UK waterways.

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