Case study:Dagenham Brook de-silting

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Location: 51° 34' 36", -0° 2' 26"
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Project overview

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Status Complete
Project web site
Themes Flood risk management, Habitat and biodiversity
Country England
Main contact forename Colin
Main contact surname Street
Main contact user ID
Contact organisation Environment Agency
Contact organisation web site http://www.gov.uk/government/organisations/environment-agency
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
Project picture

Project summary

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Reduce flood risk improve channel conveyancing, improve health and safety for light water course maintenance. Reduce flood risk and channel capacity, remove dangerous deep pockets of heavily contaminated silts. WFD driven.

A 1.5km long ditch, which historically had been over dredged and subsequently not been maintained for years due to difficult access and inconsistent deep silt, required an over haul.

It was anticipated that there was 4,400t of silt to be removed, half of which was expected to be hazardous Land and Water Services could see flaws in the historic silt test results and therefore undertook additional sampling and detailed testing which enabled the silt to be reclassified as 100% non-hazardous. Furthermore rather than dredging down to the previously over dredged hard bed level, Land & Water designed a solution which reduced the volume of silt to be removed, and therefore the cost of the works, but provided the Environment Agency with a firm and level bed for future access and maintenance (*1)

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Catchment and subcatchment

Catchment

River basin district Thames
River basin London

Subcatchment

River name Lee (from Tottenham Locks to the Tideway)
Area category 1000 - 10000 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m) 141
141 m
0.141 km
14,100 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Urban
Waterbody ID GB106038077852



Other case studies in this subcatchment: Blackhorse Lane Waterfront Park, Essex Wharf, Hackney Marsh recreation grounds, Hackney Marshes - Wick Field recreation ground, Lea Bridge Waterway Wall Improvements, Lee Navigation by Walthamstow Marshes, Springfield Marina, Tottenham Lock Floating Ecosystem


Site

Name
WFD water body codes GB106038077852
WFD (national) typology
WFD water body name Lee (from Tottenham Locks to the Tideway)
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)
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) 2000 m
2 km
200,000 cm
Project started 2009/01/01
Works started
Works completed 2009/01/01
Project completed
Total cost category 100 - 500 k€
Total cost (k€)
Benefit to cost ratio
Funding sources Environment Agency Flood and Coastal Risk Management

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
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Flood risk management
Hydromorphology
Biology
Physico-chemical Specific non-synthetic pollutants, Specific synthetic pollutants
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Removal of sediment
Floodplain / River corridor
Planform / Channel pattern
Other
Non-structural measures
Management interventions
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://http://www.land-water.co.uk/dredging-dagenham-brook 1

Supplementary Information

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