Case study:Salmons Brook River Restoration at Laymer Road

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Location: 51° 37' 46", -0° 4' 1"
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Project overview

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Status Planned
Project web site
Themes Fisheries, Flood risk management, Habitat and biodiversity, Social benefits
Country England
Main contact forename John
Main contact surname Bryden
Main contact user ID
Contact organisation Environment Agency
Contact organisation web site
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
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Project summary

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This stretch of river has been subject to a previous project undertaken by the Environment Agency’s predecessors the National Rivers Authority in 1994. This installed 5 small weirs and a toe boarding along a significant length of the river. These structures would now be seen as inappropriate due to the their impact on the morphology of the stream and the requirements of the Thames River Basin Management Plan. The proposal therefore is to removal the silt traps, regrade banks, meander river and remove the check weirs and toe boarding.

The Salmons Brook is an urban river running through Enfield, London. The river has large number of issues including water quality due to urban diffused pollution and physical modifications including weirs and hard banks. For this reason the catchment (water body) has been designated as Heavily Modified for urbanisation and flood protection in the Thames River Basin Management Plan with a target of getting the river into Good Ecological Potential by 2027. The section of river from the A10 (TQ3342994308) to Latymer Rd (TQ3389694053), has been identified as section which could be improved relatively significantly through relatively minor interventions. Once the river exists the A10 culvert it passes between 2 allotments with a small footpath running on top of the left bank. At the end of the allotments there’s a footbridge across the river where the left bank opens into a small recreation ground, with the right bank being a housing estate. The informal footpath follows the top of the left bank to Latymer Rd dividing the river from the a junior school.

The investigation needed to be completed and costed by April 2011. The consultants (whoever wins the work) will be required to undertake a detailed level survey of this stretch of river and develop options to remove these structures and restore the river to a natural morphology. The consultants should look to develop only in channel options as its not feasible to meander the channel – although regrading might be viable in some areas. Its believed that there should be two options produced 1) Complete removal or notching of the weirs, 2) replacement of the weir’s by a series of fixed gravel riffles. However if the consultants believe that there would be another viable option then they should fully investigate and present this. The consultants will also be required to investigate if the toe boarding can be removed as well.

Aspects to consider with the investigation include the reason for the installation (erosion control) of the structures and the future consequence of there removal on the surrounding areas. The consultants also need to consider cost of instillation as there is a limited budget available for installation and therefore a cost efficient solutions needs to be developed.

Monitoring surveys and results

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Lessons learnt

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Catchment and subcatchment


River basin district Thames
River basin London


River name Salmons Brook
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m) 136
136 m
0.136 km
13,600 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Suburban
Waterbody ID GB106038027960

Other case studies in this subcatchment: Alma Road Rain Gardens, Bury Lodge Wetlands, Enfield Town Park Wetlands, Glenbrook Wetlands, Grovelands Park Wetlands, Houndsden Road Rain Gardens, Laymer Road Silt Trap and Recreational Ground, Rewilding Enfield's Urban Rivers, Salmons Brook Flood Alleviation Scheme, Montagu Recreation Ground site, Salmons Brook at Grange Park


WFD water body codes GB106038027960
WFD (national) typology
WFD water body name Salmons Brook
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
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)
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Average unit stream power (W/m2)

Project background

Reach length directly affected (m) 500 m
0.5 km
50,000 cm
Project started 2008/01/01
Works started
Works completed
Project completed
Total cost category
Total cost (k€)
Benefit to cost ratio
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Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
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Reasons for river restoration

Mitigation of a pressure Flood risk management, Pollution incident, Urbanisation
Hydromorphology Continuity for sediments, Channel pattern/planform, Substrate conditions
Physico-chemical Specific non-synthetic pollutants, Specific synthetic pollutants
Other reasons for the project Recreation


Structural measures
Bank/bed modifications Toeboard removal, Weir removal
Floodplain / River corridor
Planform / Channel pattern
Non-structural measures
Management interventions
Social measures (incl. engagement) Improved public access
Other Economic benefits


Hydromorphological quality elements

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Before measures After measures Qualitative Quantitative

Biological quality elements

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Physico-chemical quality elements

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Any other monitoring, e.g. social, economic

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Monitoring documents

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Supplementary Information

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