Maintenance dredging forms an important part of the Commissioners’ channel maintenance works. It is critical to the efficient operation of the Commissioners’ artificially pumped and gravity systems to dredge silt deposits from channel beds, as over time watercourses and drainage channels silt deposits naturally build up as it is carried into them by water flows.
The gradual build-up of silt and decaying plant material along the channel bed prevents efficient water conveyancing during heavy rainfall and pumping events, and can also make statutory navigation of the Commissioners’ system difficult.
The Commissioners periodically undertake channel bed surveys of their watercourses. The survey information is plotted and used to help prioritise and programme future maintenance dredging works, where it is required.
Most maintenance dredging work is pre-planned to be undertaken during the colder winter months. This helps to reduce the impact on local wildlife habitat, ecology and navigation traffic.
Contractors are used to undertake maintenance dredging works, using Long Reach Excavators. They are able to reach out into the water channels and efficiently remove silt to a uniformed pre-determined bed level.
The silt dredgings at this point have a high-water content, and are placed along the back of the grass embankments to dry out sufficiently until they can be re-handled later in the summer months.