Case study:Ironbridge Farm
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- 1 Project overview
- 2 Image gallery
- 3 Catchment and subcatchment
- 4 Site
- 5 Project background
- 6 Reasons for river restoration
- 7 Measures
- 8 Monitoring
- 9 Additional documents and videos
- 10 Additional links and references
- 11 Supplementary Information
|Project web site||http://www.essexrivershub.co.uk|
|Themes||Habitat and biodiversity, Water quality|
|Main contact forename||Kieren|
|Main contact surname||Alexander|
|Main contact user ID||User:KierenAlexander|
|Contact organisation||Essex Wildlife Trust|
|Contact organisation web site||http://www.essexwt.org.uk|
|Parent multi-site project|
| This is a parent project
encompassing the following
The river restoration at Ironbridge Farm builds on the work undertaken at Little Waltham meadows on the River Chelmer and the nearby Local Nature reserve at Bocking Blackwater.
As with all of these works the aim of the project is to improve the water-body under the Water Framework Directive. Currently the River Pant is failing under Water Framework Directive for a number of reasons including diffuse pollution, fish passage, point source and physical modification. It should be noted that this area does suffer from low flows during the summer months, especially if the Abberton scheme which transfers water from the Ouse to Abberton is closed.
There are some local issues with the river in this area, that are largely typical of those found elsewhere in Essex. Namely the disconnection of the river from the surrounding floodplain, this has led to a reduction in quality and type of Riparian habitat, in this case specifically wet woodland which is drying out and fen meadows which are decreasing in number and quality. Interestingly and of some note, the site at Ironbridge Farm and the surrounds are a Local Wildlife Site (LoWS) this means they have been recognised as an outstanding site in the context of Essex. Largely the site is notified for its mosaic of habitat but a key element of this is the presence of wet woodland and Fen meadow. So, besides contributing to raising the WFD status of the site, it is also contributing to the rehabilitation of the LoWS in the shape of an enhanced wet woodland and and enhanced Fen meadow.
In order to achieve this, a plan has been designed which will increase the seasonal inundation and flooding of the woodland and fen meadow. This will have the multi benefits of reconnecting the floodplain, reducing flooding and improving water quality.
A simple pipe will be installed which has been set to a level which will not only protect low flows but achieve the desired ecological effects. The level of the pipe was calculated by taking measurements on days of known flows and supported by Mannings equation.
It is hoped that the pipe level (nominally 44.30OD) will allow the site to flood 4 or 5 times during the winter months, an existing land drain will also be diverted to feed into the woodland.
In addition to the installation of a pipe there will also be some limited earthworks to help the water move around the site in an effective manner and also to provide further enhancement of the local wildlife site. There will be around 15 to 20cm's taken off the existing field surface to delineate a channel and hold water. The spoil created by this will then be used to create a small bund which will stop any uncontrolled water spreading across the floodplain.
A number of considerations had to be considered before undertaking this work, most notably in this case the presence of trees on the site. This resulted in a number of tree assessments being undertaken in order to manage and mitigate any impact on the tree's including HERAS fencing, root protection tracks and a number of arrangements put in place to protect these trees.
Work should be undertaken in August 2015, all the necessary consents are in place and a contractor has been appointed to undertake the works.
Monitoring surveys and results
A key component of this project is to rehabilitate and enhance the LoWs including Fen Meadow and Wet woodland. Therefore any monitoring will focus on any improvement is this habitat. There will also be fixed point photography, before, after and as the site develops.
There are some significant limitations to Manning's equation, especially in waters that are heavily impounded as most Essex rivers are. This means that any attempts to use this equation to work out the flow and height of the water is limited, this adds a degree of complication to any water height and flow calculations. If this is the case, then water heights from specific days or contact with the local EA hydrologist is recommended to allow real time calculations to be taken at times of known flow.
Catchment and subcatchment
Select a catchment/subcatchment
Other case studies in this subcatchment: Millfield Plantation 2, Plough Hill Farm Meander and Wet meadow restoration
Cost for project phases
Reasons for river restoration
Hydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Additional documents and videos