Case study:Ironbridge Farm

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Location: 51° 55' 42", 0° 31' 6"
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Project overview

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Status In progress
Project web site http://www.essexrivershub.co.uk
Themes Habitat and biodiversity, Water quality
Country England
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
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
The wet woodland at Ironbridge which will be enhanced

Project summary

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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

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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.

Lessons learnt

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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.


Image gallery


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Catchment and subcatchment

Catchment

River basin district Anglian
River basin Combined Essex

Subcatchment

River name Pant
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m) 130
130 m
0.13 km
13,000 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB105037041180



Other case studies in this subcatchment: Millfield Plantation 2, Plough Hill Farm Meander and Wet meadow restoration


Site

Name Ironbridge Farm
WFD water body codes GB105037041180
WFD (national) typology
WFD water body name Pant
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body Yes
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present Yes
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 250
250 m
0.25 km
25,000 cm
Project started 2012/04/01
Works started 2016/08/07
Works completed
Project completed
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design Essex Wildlife Trust Kieren Alexander
Stakeholder engagement and communication Essex Wildlife Trust Kieren Alexander
Works and works supervision Essex Wildlife Trust Kieren Alexander
Post-project management and maintenance Essex Wildlife Trust Kieren Alexander
Monitoring Essex Wildlife Trust Kieren Alexander



Reasons for river restoration

Mitigation of a pressure
Hydromorphology Structure & condition of riparian/lake shore zones, Channel pattern/planform
Biology Invertebrates, Macrophytes, Fish
Physico-chemical Specific non-synthetic pollutants
Other reasons for the project Habitat creation, Landscape enhancement


Measures

Structural measures
Bank/bed modifications Habitat restoration
Floodplain / River corridor Creation of backwaters, Creation of wetland, Creation of pond
Planform / Channel pattern Habitat restoration, Creation of backwater
Other UK BAP habitat creation/restoration
Non-structural measures
Management interventions Ensuring biodiversity, Woodland management, Promoting riparian vegetation
Social measures (incl. engagement)
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



Additional documents and videos


Additional links and references

Link Description
http://www.essexrivershub.org.uk For more information on this and other projects in Combined Essex catchment

Supplementary Information

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