Case study:Ravensbourne/Pool confluence weir bypass channel

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Location: 51° 26' 22.64" N, 0° 1' 34.70" W

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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	No

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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 Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this 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) 132132 m <br />0.132 km <br />13,200 cm <br /> 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 Edit 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 Edit project background Reach length directly affected (m) 10 m0.01 km <br />1,000 cm <br /> 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 Edit reasons for restoration Mitigation of a pressure Barriers to fish migration Hydromorphology Biology Fish Physico-chemical Other reasons for the project Measures Edit 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 Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit 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 Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information