Case study:Pymmes Park Wetlands

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Location: 51° 37' 5.38" N, 0° 4' 15.68" W

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Project overview

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Status	Complete
Project web site
Themes	Environmental flows and water resources, Flood risk management, Habitat and biodiversity, Monitoring, Social benefits, Water quality, Urban
Country	England
Main contact forename	Ian
Main contact surname	Russell
Main contact user ID
Contact organisation	London Borough of Enfield
Contact organisation web site	http://enfield.gov.uk/
Partner organisations	London Borough of Enfield, Friends of Pymmes Park, Thames21
Parent multi-site project	Case_study:Rewilding Enfield's Urban Rivers
This is a parent project encompassing the following projects	No

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Project summary

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The Moore Brook, is a lost river, which drains a catchment area of roughly 350 hectares and flows from Winchmore Hill to Edmonton (Pymmes Park Lake) passing through Firs Farm Recreation Ground. As it drains a large catchment, the Moore Brook picks up a large amount of urban runoff contaminated with phosphates, nitrates, heavy metals, hydrocarbons and oils from footpaths and roads. It has been culverted since the 1950’s, and as a result has been prone to plumbing misconnections. This pollution accumulates throughout the catchment causing problems further downstream when it enters Pymmes Park Lake, and is particularly prominent during periods of dry weather. The London Borough of Enfield highlighted that the ongoing complaints from the smell and pollution of the lake required a holistic approach in managing. This lake directly outfalls into Pymmes Brook, one of the most polluted tributaries of the River Lea.

The London Borough of Enfield and Thames Water took on large scale project to resolve possible misconnections in the catchment. 800 misconnections were resolved, but to manage residual pollution from road runoff and additional misconnections a series of cascading wetland cells to capture dry weather flows, immobilise and filter pollutants from the stream before it entered the lake were introduced.

A total catchment of 294Ha is treated by the four cascading wetland cells. 216Ha of this catchment passes through the Firs Farm Wetlands, which introduces a “first treatment phases” upstream of the Lake. A total of 0.6Ha of wetlands has been constructed across the Moore Brook Catchment, in Pymmes Park and Firs Farm. As a result, Pymmes Park Wetlands filters around 85% of all dry weather flows entering the lake.

Monitoring surveys and results

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London Borough of Enfield has compiled pollution records and water quality data from the past, and has been collecting water quality data on Biological Oxygen Demand, Suspended Soilds and Nutrients for three years.

A Water Quality monitoring programme is now in place with Thames21, measuring parameters such as:

- Dissolved Oxygen and Biological Oxygen Demand

-Nutrients (nitrates, phosphates and ammonia)

- Faecal Coliforms

Lessons learnt

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Image gallery

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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 Pymmes Brook (Salmons Brook to Lee, includes Part of Lee Navigation B) Area category 10 - 100 km² Area (km2) Maximum altitude category Less than 100 m Maximum altitude (m) 2626 m <br />0.026 km <br />2,600 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Urban Waterbody ID GB106038027910 Other case studies in this subcatchment: Firs Farm Wetlands Site Edit site Name Pymmes Park Wetlands WFD water body codes UKGB106038027910 WFD (national) typology WFD water body name Pymmes Brook (Salmons Brook to Lee, includes Part of Lee Navigation B) Pre-project morphology Closed culvert Reference morphology Desired post project morphology Heavily modified water body Yes National/international site designation Local/regional site designations Protected species present No Invasive species present No Species of interest Dominant hydrology Surface Water Runoff Dominant substrate Clay, Gravel River corridor land use Urban - Culverted, Parklands, Grassland 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 Poor Water Quality of Lake Hydromorphology Quantity & dynamics of flow Biology Physico-chemical Oxygen balance, Nutrient concentrations, PH, Biological Oxygen Demand, Total Suspended Solids, Heavy Metals, Hydrocarbons Other reasons for the project Improving Health and Wellbeing of local park users Measures Edit Measures Structural measures Bank/bed modifications Deculverting, Ponds and pools inside the wetland Floodplain / River corridor Reedbed creation, Creation of wetland, Creation of wetland, Deculverting, Extensive planting, Sustainable urban drainage ponds (SUDs), Floodplain creation Planform / Channel pattern Other Non-structural measures Management interventions Reduced pollution Social measures (incl. engagement) education; public amenity and perception, Community involvement 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