Case study:Ravensbourne/Pool confluence weir bypass channel

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Location: 51° 26' 23", -0° 1' 35"
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Project overview

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Status Complete
Project web site
Themes Fisheries
Country England
Main contact forename Peter
Main contact surname Gray
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
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Project summary

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The existing bypass channel does not function. Requires a redesign to push more flow through it and to make it more attractive to fish. This structure just upstream of the confluence of the Ravensbourne with the Pool River. It is a sloping-back weir with a head loss of about 437 mm. Some eel passage is likely to be possible at low flows, however it is likely to be a significant barrier to fish passage.

Monitoring surveys and results

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Lessons learnt

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August 2012 update - Confluence bypass channel is not complete, due to the presence of Japanese Knotweed the project could not be totally completed, a deflector was put in and the channel dug but it is not working. In base of visit in August: the channel is dry.


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Catchment and subcatchment

Catchment

River basin district Thames
River basin London

Subcatchment

River name Ravensbourne (Catford to Deptford)
Area category 100 - 1000 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m) 132
132 m
0.132 km
13,200 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Urban
Waterbody ID GB106039023270



Other case studies in this subcatchment: Broadway Fields/ Seagers Distillary, Catford Greyhound Stadium, Cornmill Gardens (QUERCUS), Ladywell Fields (QUERCUS), Ladywell Fields Phase 2, Ladywell Fields to Cornmill Gardens, Ladywell Fields toeboarding, Lewisham College weir, Linear Park, QUERCUS Ravensbourne... further results


Site

Name
WFD water body codes GB106039023270
WFD (national) typology
WFD water body name Ravensbourne (Catford to Deptford)
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) 10 m
0.01 km
1,000 cm
Project started 2012/01/01
Works started
Works completed 2012/01/01
Project completed
Total cost category 10 - 50 k€
Total cost (k€)
Benefit to cost ratio
Funding sources Defra WFD funded

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 Barriers to fish migration
Hydromorphology
Biology Fish
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications
Floodplain / River corridor
Planform / Channel pattern Bypass channel
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

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Before measures After measures Qualitative Quantitative


Monitoring documents



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Supplementary Information

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