The Dredging Debate
Dredging is not the silver bullet the Environment Agency keep encouraging us to believe it is. The Wildlife Trusts believe that this practice could make matters worse. Dredging - a reality check, produced by the Chartered Institution of Water and Environmental Management, sets out a clear message that rivers need to be managed in a sustainable way, and it's vital to restore many of the natural process lost through draining land for agriculture, building in the flood plain and failing to address the issues of increased surface water runoff. Through our work on Living Landscapes we have been restoring and conserving river habitats helping better manage flooding at the local level, benefitting people and wildlife.
A single solution is not the answer - a sustainable approach to the management of river systems is required -only through a holistic approach to river management will it be possible to solve the problems of flooding and prevent the misery experienced by so many people in recent winters.
A guidance note from the Environment Agency clarifies what dredging really means and some of the recent studies they have undertaken into its effectiveness. We will continue to keep members up to date on the issue and to invest in our nature reserves and surrounding landscapes to ensure nature's natural processes help communities adapt to the increased flood risk associated with climate change.
Across our three counties work goes into alleviating flood water and there are natural flood attenuation schemes where the natural environment can be used as a sponge forming water storage areas:
Wicksteed Water Meadow – reinstating the meadow and reconnecting with the River Ise (Nene Catchment)
The newly restored water meadow at Wicksteed Park near Kettering, last used over 100 years ago, was originally designed to be intentionally flooded to make the most of the nutrients and warmth in the river water. Now although we can’t intentionally flood the meadow, we can take the opportunity of high river levels to let the water in. Flooding the meadow helps to maintain the wet grassland and swamp conditions that are increasingly uncommon in our highly managed countryside and fantastic for wildlife. It also reduces the amount of water flowing downstream towards the edge of Kettering and Wellingborough.
Barnes Meadow – creation of meanders and wetland areas connected to the river
The river once took a very different course through Northampton. Road improvements and flood defence schemes have moved the river over the years, leaving dead ends like the backwater at Barnes Meadow in Northampton. The backwater is also responsible for feeding a series of ditches and scrapes in the meadow, which flood with water when levels are high, creating habitat for insects and birds. The backwater itself provides a quiet, still area in times of flood which is a refuge for fish and prevents them from being washed downstream.
Nene Valley Backwaters project – dredging and reinstating backwaters / back channels
Over at least the last 250 years the river Nene has been altered to provide navigation for boats. These changes include the straightening of rivers to remove tight meanders, and has left behind the remnant channels as backwaters. Backwaters provide valuable habitat for a range of wildlife including insects, plants, fish and birds, but they have a tendency to fill with silt and gradually dry out. Through a partnership with the Environment Agency, and later through the Nene Valley Nature Improvement Area, we have been identifying, surveying and then enhancing backwaters along the river Nene to improve the wildlife on the river and to increase resilience to flooding, drought, and other effects of climate change.
Meadows at Upper Heyford – arable reversion to flower rich meadows – allowed to flood under periods of peak flow
An area of 13.8ha of arable land adjacent to the river Nene at Upper Heyford was restored to flower-rich hay meadows in 2008. The area has flooded every winter, and sometimes at other times of year, and when it was under arable production each flood would not only damage the crop but take soil and chemicals into the river. Since becoming a meadow the flooding is welcomed, and helps to create suitable conditions for plants like great burnet. The flood water is held on the land for longer and rather than taking pollutants back into the river, the water is actually cleaned by being slowed down and filtered across the meadow.
Nene Valley Gravel Pits such as Irthlingborough Lakes and Meadows– all allowed to flood under peak flow and act as key water storage areas in the Nene Valley
Many of the restored gravel workings in the Nene Valley were designed to act as flood storage areas. The gravel pits themselves and the low lying land around them can hold large quantities of water in times of flood, letting it slowly back into the river when levels begin to subside. This can have benefits, but at the wrong time of year can cause devastation to ground nesting birds.
Great Fen, Cambridgeshire, has an efficient managed system of flood control and drainage
Over a long period, the Great Fen is slowly creating a new landscape to benefit wildlife and people. Where this is happening, water is carefully controlled to create a range of habitats (from large areas of dry pasture to much smaller areas of reed bed and pools of open water) and to protect surrounding neighbouring farm land, houses and infrastructure. At the moment, Woodwalton Fen National Nature Reserve – an internationally important wildlife site and part of the Great Fen - is used to store water during heavy rainfall; however, it is too small to cope with the extreme rainfall events that are becoming more and more frequent. An alternative that continues to protect local people and land is needed. The Great Fen is working closely with the Environment Agency and the Middle Level Commissioners (both Great Fen Project Partners) to identify and create new water storage areas in the Great Fen for times of heavy rainfall. Reedbed, for example, has the capacity to absorb excess water without lasting detriment to wildlife.