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Contact for More Information: darrent@essexwt.org.uk
The Chelmer Valley Nature Reserve is a small local nature reserve that runs through the centre of Chelmsford; it incorporates a number of habitats including some relic fen meadows and wet woodland but also a large amount of amenity grassland.
A key feature of this Local Nature Reserve is the River Chelmer which runs through the park for around 2.5km before heading into Chelmsford City Centre.
The river is heavily impounded and is characterised by slow flows and historically has been deepened, widened and dredged leading to poor floristic diversity. The aim of this project was to attempt to reverse this by introducing faster flowing water, providing edge habitat and reconnecting the floodplain.
We achieved this by putting in a number of interventions, including bank reprofiling. In the case of the project at Chelmer Valley Local Nature Reserve, this meant forming and creating five berms out of historical dredgings. The soil is then placed into the main river bank and compacted using an excavator, to approximately a third of the channel.
The main purpose of these berms was to improve local flow velocity. This has a number of benefits for the river; the sped up flow prevents silt from settling on the riverbed and exposes gravels. These exposed gravels and faster flowing columns of water are the most biodiverse areas in the river providing great habitat for insects and fish, especially fish fry.
In addition to constricting the flow and revealing gravels; these features also provide a number of other benefits. They provide an interface between the water environment and the terrestrial environment, allowing flora and other interesting flowers to develop, offering habitat for a wide range of invertebrates both aquatic and terrestrial.
As a final complementary feature, the bank reprofiling also reconnects the floodplain, allowing floodwater to be stored in the floodplain away from houses and property. Historical management of the site means that a lot of water is funnelled down the river at the same time until it hits a hard object when it hits the hard object such as a sluice or a weir it backs up, this means that rivers can sometimes flood. By allowing water onto the floodplain higher up the catchment it prevents the water getting to the structure quite so quickly and can reduce flooding. Also by storing water in the floodplain it also means that we are hopeful of creating new habitat, in this case, a mosaic of wetlands and fen meadows.
The project was undertaken in March 2017, with the earthworks lasting about a week. Within four months the berms and bank re-profiling had completely vegetated over and had completely stabilised to provide new habitat.
The new features form a new bankside, gently sloped and reduce the channel by about a third. This makes the channel narrower and the flow quicker. There is no need to bring in vegetation as the natural seed bank will quickly establish and bind the new feature together. Angles and length vary depending on what the characteristics of the site are. In locations like here at Chelmer Valley LNR, these solutions are quick, simple and easy ways to establish some flow dynamics. Perhaps more suitable than woody debris in these locations due to depth of the channel and width of the channel which would offer some logistical challenges to installing woody debris.
Within four months the berms and bank re-profiling had completely vegetated and had stabilised to provide new habitat.
This project was funded by the Catchment Partnership Action fund and was undertaken by the Essex Wildlife trust in partnership with the Environment Agency on behalf of the Combined Essex Catchment Partnership (Essex Rivers Hub).
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The topics below represent the pressures that many waterbodies in the Combined Essex catchment face. They have been divided into six main categories, but it is quite often that these categories can overlap as pressures relate to each other.
