Case study:River Wandle: Butter Hill Phase 3

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Location: 51° 22' 13.33" N, 0° 9' 35.76" W

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity, Social benefits, Urban
Country	England
Main contact forename	Tim
Main contact surname	Longstaff
Main contact user ID
Contact organisation	Wandle Trust
Contact organisation web site	http://www.wandletrust.org
Partner organisations	Environment Agency, Defra, Thames Water, National Lottery's Heritage Lottery Fund
Parent multi-site project	Case_study:Butter Hill restoration project, River Wandle
This is a parent project encompassing the following projects	No

Before & After Butter Hill Phase 3 Works © Wandle Trust

Project summary

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This Project is part of a larger scheme with the overall aim of establishing a population of brown trout in the Carshalton arm of the River Wandle for the first time in over 80 years. For more background on this larger scheme, please refer to the parent project "River Wandle Restoration Project".

Flood risk and hydraulic assessment of the weir and fish pass were carried out in conjunction with Matt Horritt Consulting. Works were delivered with the help of appointed contractors Aquamaintain Ltd under the supervision of South East Rivers Trust staff.   The weir at Butter Hill bridge was partially lowered to restore natural flow to the upstream channel and the fish pass modified to improve its efficiency.

Upstream of the weir the over-straight, over-wide channel was narrowed and modified to create a meandering sequence using a combination of gravel, hazel faggots, chestnut posts and coir geotextile with silt from the channel and brash as backfill.   The banks on both sides of the channel were then re-graded to create marginal and transitional habitats. A variety of marginal plant species were introduced to assist with naturalisation by a team of 15 volunteers.

Downstream, for 300 m, channel narrowing and meandering was continued and gravel and Large Woody Debris was introduced along the whole reach to further diversify the river flow and replicate natural hydromorphological processes, creating habitats for invertebrates and all life stages of fish.

Trees were also removed in phases over a two year period to increase light in selected places and encourage plant growth along the whole 500 m reach.

Monitoring surveys and results

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Please see the parent project (River Wandle Restoration Project) for the final results on this work, combined with the other phases.

Lessons learnt

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Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name WFD water body codes WFD (national) typology WFD water body name Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body National/international site designation Local/regional site designations Protected species present Invasive species present 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) Project started Works started Works completed Project completed Total cost category Total cost (k€) Benefit to cost ratio Funding sources 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 Hydromorphology Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern 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