Case study:Enhancement of the River Crouch following a pollution incident

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Location: 51° 37' 12", 0° 32' 5"
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Project overview

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Status Complete
Project web site http://www.vimeo.com/106173104
Themes Fisheries, Habitat and biodiversity, Hydromorphology, Social benefits
Country England
Main contact forename Trevor
Main contact surname Bond
Main contact user ID User:Tbond
Contact organisation Environment Agency
Contact organisation web site http://www.gov.uk/government/organisations/environment-agency
Partner organisations Basildon District Council, Essex Wildlife Trust
Parent multi-site project
This is a parent project
encompassing the following
projects
No
A gravel bar formed at the confluence of the River Crouch and Runwell Brook

Project summary

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The River Crouch at Wickford Memorial Park is a high priority waterbody that is currently failing to achieve its Water Framework Directive (WFD) objectives for hydromorphology. In addition, the river is failing for a number of water quality elements including dissolved oxygen and phosphates. Following a pollution incident in 2009 and the subsequent court case, Anglian Water Services (AWS) volunteered to commit funding of £15,000 for a restoration project on the stretch of the Crouch immediately downstream of the Memorial Park Bridge. The principle aim of this project was to improve the ecology of the River Crouch at Wickford by employing targeted, low-cost river restoration techniques. More broadly, the project has helped fulfil the objectives of the WFD by focusing on those quality elements for which it is currently failing.

The project involved the installation of several large woody-debris flow deflectors. Because of the high flood risk nature of the upstream town of Wickford, particular care was given to the stability of the features created. A belt and braces approach to the project ensured ecological gains without compromising the flood-risk function of the River Crouch.

Monitoring surveys and results

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Lessons learnt

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Image gallery


The existing river had a straight planform
The first step in the deflector installation was to dig out a trench in the bank
The second step in the deflector installation is to lower the large woody-debris into the trench
Step three in the deflector installation is to stake and brace the large woody-debris. By linking all the elements together and using screws to fasten the material, the likelihood of structure failure is minimised
The final step is to cover the debris with soil and then repair the bank to its former condition
The deflectors were set at different heights in the water so that they would operate under a range of flow conditions
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Catchment and subcatchment

Catchment

River basin district Anglian
River basin Combined Essex

Subcatchment

River name River Crouch
Area category 10 - 100 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 77
77 m
0.077 km
7,700 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Improved grassland
Waterbody ID GB105037028550



Site

Name River Crouch
WFD water body codes GB105037028550
WFD (national) typology Low, Small, Calcareous
WFD water body name River Crouch
Pre-project morphology Straightened
Reference morphology Straightened
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present Yes
Species of interest
Dominant hydrology Groundwater
Dominant substrate Gravel
River corridor land use Urban
Average bankfull channel width category 5 - 10 m
Average bankfull channel width (m)
Average bankfull channel depth category 2 - 5 m
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) 600
600 m
0.6 km
60,000 cm
Project started 2012/12/21
Works started 2014/09/08
Works completed 2013/09/20
Project completed 2014/10/10
Total cost category 10 - 50 k€
Total cost (k€)
Benefit to cost ratio
Funding sources Anglian Water

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design Less than 1 k€ Environment Agency Trevor Bond
Stakeholder engagement and communication Less than 1 k€ Environment Agency Michael Neale
Works and works supervision 10 - 50 k€ Environment Agency Tony Miles
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Pollution incident
Hydromorphology
Biology
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Bank reprofiling
Floodplain / River corridor
Planform / Channel pattern
Other Woody-debris flow deflectors
Non-structural measures
Management interventions
Social measures (incl. engagement) Interpretation boards
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



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Supplementary Information

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