Natural processes in many rivers means silt will return and accumulate in the same places very quickly, sometimes only weeks after dredging and desilting is carried out, therefore any increase in channel capacity will be short-lived. In the majority of cases, they are not the most efficient or sustainable ways of reducing flood risk and may actually increase flood risk to downstream communities. When used with other flood risk management measures as part of a catchment based approach dredging and desilting can be effective and justified. Does dredging and desilting prevent flooding?

Therefore the level of dredging and desilting has decreased in the UK over recent decades. In the past this has sometimes come with unintended consequences including increasing flooding downstream.ĭredging and desilting are not as effective at reducing flood risk as other options, are often expensive and can be harmful to the environment. In the UK, dredging and desilting have historically been carried out for a broad range of reasons: to drain land, maintain flows to mills, abstract sand or gravel for construction or to improve navigation, in addition to preventing flooding. It is undertaken less frequently and is a bigger exercise. We use dredging to describe removing a range of materials or for making the channel larger by removing the bed and channel side material.

Dredging and desilting are methods that we use to remove an accumulation of silt material, such as fine gravels or soils that have been washed into rivers from surrounding land in the catchment, from the bottom of rivers to temporarily increase the flow.ĭesilting is usually undertaken more frequently to remove recent deposits of silt to the bed level of a river.

Why do we dredge up the past