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Dredging

Dredging, or sediment management, is the removal of sediment from a river channel.

Rivers naturally change shape and direction through time. They move sediment, comprising of silt, sand, gravel, pebbles, cobbles, and boulders, when there is high flow. The amount of sediment moved will normally increase during and after large floods, often resulting in significant changes in rivers.

Climate change is resulting in more extreme weather and increased flood events, which increase the rate at which rivers change. We are already starting to see these changes and we need to adapt.

Dredging and flooding

Dredging is often viewed as the solution to flooding on the basis that the channel is made bigger so it can contain more water.

The space created by removing sediment from a river is often small compared to the the volume of water generated during flood events. Even if dredging reduces flood risk locally, it is likely that this simply passes the problem downstream.

While dredging is required in some circumstances, it is usually not the most effective or sustainable approach to managing flood risk in a catchment.

Changing the way sediment is transported in rivers often results in unexpected changes, such as increased erosion that can spread upstream and downstream. This eroded sediment can quickly refill the space that was created by dredging, as well as damaging river habitats and ecosystems, worsening the situation.

Natural processes, involving the erosion, transport, and deposition of sediment within rivers mean that any benefits of dredging are often short term.

For more information, you can listen to the Farming and Water Scotland podcast which involved SEPA colleagues discussing how land managers can work with us to manage water flow on farm. Focusing on what farmers can do regarding ditches, drainage and dredging on farm we discuss the rules and guidelines which must be followed. Through our discussion we focus on the management actions, which can be done without involvement from SEPA, to the licencing process.

How we regulate dredging

Dredging is a regulated activity. In most cases there are conditions or rules within an authorisation which must be complied with.

There are some activities you can do to reduce the risk of flooding or increase resilience and recovery from flooding on a river where no authorisation is required, such as clearing debris, vegetation, and maintaining man-made ditches. There are also some small-scale sediment removal/dredging activities which are subject to General Binding Rules (GBRs), such as removing sediment from within ten metres of a culvert, where a set of rules must be followed, but no application is required.

Where written application for authorisation is required, we will assess the risk of impacts to the water environment and ensure that appropriate mitigation measures are deployed to prevent pollution.

More information on authorisations and the application process can be found on the Engineering section of our website.

Get in touch

We are here to help. We can advise you and help with the application process or to discuss the General Binding Rules.

Let's work together to ensure our water environment is protected, and that we are adapting to the challenges posed by the changing climate.

Dredging guidance