Case study:Saving Chiswick Eyot

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Location: 51° 29' 15.00" N, 0° 14' 45.00" W

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Project overview

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Status	In progress
Project web site	http://www.savingchiswickeyot.com
Themes	Economic aspects, Environmental flows and water resources, Fisheries, Flood risk management, Habitat and biodiversity, Hydromorphology, Land use management - forestry, Monitoring, Social benefits, Water quality, Urban
Country	England
Main contact forename	Martin
Main contact surname	Richardson
Main contact user ID	User:Mobilitydream
Contact organisation	Natural History Museum
Contact organisation web site	http://www.nhm.ac.uk
Partner organisations	Royal Holloway University of London, MoLA, Fullers Brewery, University of Leicester, Thames21, Port of London Authority, DHI, Thames Tideway, The British Geological Survey
This is a parent project encompassing the following projects

Eyot erosion

Project summary

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Project team

Dr. Dave Morritt, Royal Holloway University of London. Dr. Paul Clark, Natural History Museum, London. Martin Richardson, PhD student RHUL & NHM.

Project

Chiswick Eyot is a small, historically important island in the Thames near Chiswick Mall that is subject to erosion. We are working with an ‘ecosystem’ of partners to address the problem of maintaining the island employing best practice techniques. An initial 3D scan of almost the entire island was conducted in 2016 in association with the University of Leicester and Leica Geosystems. The scan was repeated in 2017. Analysis of the scans will provide greater understanding of the processes at work and enable visualisation of any changes occurring as well as determination of the rate of erosion. In addition, several hundred digital photographs were taken of areas of particular interest over a 3 year period to provide a visual record, these will also be used to develop point clouds as supplementary data.

Bi-monthly conventional topographic surveys of part of one bank were undertaken by MoLA in 1999 and 2000 allowing for decadal scale assessment of the erosion rate. High resolution aerial photographs and digitized historical Ordnance Survey maps are available dating back to at least the 1930s and these will be used to assess changes in surface area and any migration of the banks generally. We have engaged with the local community and formed partnerships with other organisations including Thames 21, the River Restoration Centre, Leica Geosystems, DHI, MoLA, and Royal Holloway University of London.

Monitoring surveys and results

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Very accurate baseline surveys have been completed.Preliminary assessment indicates a current rate of retreat of the banks at around 1m per decade, or approximately 10cm annually.A large amount of material has accumulated behind the facines which are being well maintained.

Lessons learnt

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Restoration work using traditional willow withes has resulted in improved overall appearance and accretion to some areas of the bank. Vegetation is not growing in the silt perhaps because of a lack of oxygen. Seepage from the bank toe area is keeping the silt mobile in some areas. The current approach employed by Thames21 of incremental maintenance appears to be successful and demonstrates a very good cost vs. benefit ratio, especially since partners have started to make contributions towards costs. Withies planted on the flat surface of the island by the Old Chiswick Preservation Society are growing well and the willow holt, which is pollared annually, appears to be in very good condition. The withies produced by the pollarding are then bundled by the OCPS and volunteers and used to provide structure behind the fascines.

It might be useful at this point to consider additional techniques such as rolls of rocks (rocks bundled into mesh 'socks') at the areas of the bank toe with seepage but it is unknown currently if this is permitted in the area. Thames21 has also mentioned using different species of aquatic plants.

Image gallery

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Tree and slumping bank

Detail holes in the banks of Chiswick Eyot.

Using the Leica P40 scanner

Accretion behind restoration structures on the north bank of the Eyot

Complex erosion pattern

Comparison 2002 to 2010 bottom of bank

Detail from a laser scan 2016

LiDAR data

Photogrammetry of part of the bank 2016

Photogrammetry point cloud of restored bank 2016

Photogrammetry model made this year of the East bank

More detail of the East bank. Photogrammetry 2017

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 Thames Middle Area category Less than 10 km² Area (km2) Maximum altitude category Maximum altitude (m) Dominant geology Ecoregion Great Britain Dominant land cover Urban Waterbody ID GB530603911402 Other case studies in this subcatchment: Barking Creek near A13, Barking Creekmouth, Chambers Wharf, Cuckolds Haven Nature Area, Greenwich Peninsula, Lower River Roding Regeneration Project, Mill Pool, Wandsworth Riverside Quarter Site Edit site Name WFD water body codes GB530603911402 WFD (national) typology Intertidal WFD water body name Thames Middle 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 Yes Species of interest Chinese mitten crab (Eriocheir sinensis) Dominant hydrology Dominant substrate River corridor land use Urban 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) 290290 m <br />0.29 km <br />29,000 cm <br /> Project started 2014/12/23 Works started 2015/06/01 Works completed Project completed Total cost category 50 - 100 k€ Total cost (k€) Benefit to cost ratio Funding sources Commercial partners. Local charities. Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design 1 - 10 k€ Natural History Museum Paul Clark Stakeholder engagement and communication Less than 1 k€ Royal Holloway University of London Martin Richardson Works and works supervision 100 - 500 k€ Natural History Museum Diana Catovan Post-project management and maintenance 1 - 10 k€ Natural History Museum Paul Clark Monitoring 1 - 10 k€ Natural History Museum Diana Catovon Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Invasive species Hydromorphology Structure & condition of intertidal zone Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Bank stabilisation, Restoration of natural vegetation, Removal of invasive plants, Removal of invasive species Floodplain / River corridor Planform / Channel pattern Bank restoration Other Non-structural measures Management interventions reducing bank side collapse (another main source of sediment) Social measures (incl. engagement) Awareness raising, Community involvement, Citizen participation in the restoration project 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