Case study:River Ogwen and Nant Francon

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Location: 53° 7' 56.89" N, 4° 1' 53.96" W

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Flood risk management, Land use management - agriculture
Country	Wales
Main contact forename	Hugh
Main contact surname	Jones
Main contact user ID
Contact organisation	Natural Resources Wales
Contact organisation web site	http://naturalresourceswales.gov.uk/
Partner organisations	National Trust, Environment Agency
Parent multi-site project
This is a parent project encompassing the following projects	No

Restored bed level and bank profile following restoration (Nov 2012)

Project summary

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The Ogwen is in a mountainous location of Snowdonia below Llyn Ogwen (Lake Ogwen), and flows northwards through the Nant Ffrancon valley. During the 1960s the river was deepened by dredging over a 4km length downstream of the waterfall in an attempt to reduce the frequency of flooding over the valley floor to improve livestock grazing. Over the following 30 years the river flushed virtually all bed gravels through the system and scoured the river bed and banks. The reach became severely denuded of any stable habitat for flora and fauna, the once thriving salmon fishery declined and flooding was still troublesome to farmers. Four boulder cascades were created and pool and riffle sequences created in the upper reach. Some runs of gravel were introduced and shoals were created on the inside of bends. A major erosion site was reinstated using a willow mattress technique.

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Restored Island - Nov 2012

Restored section - Nov 2012

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district Western Wales River basin North West Wales Subcatchment River name Ogwen - upper Area category 10 - 100 km² Area (km2) Maximum altitude category 1000 - 2000 m Maximum altitude (m) 10361,036 m <br />1.036 km <br />103,600 cm <br /> Dominant geology Siliceous Ecoregion Great Britain Dominant land cover Acid Grassland Waterbody ID GB110065054160 Site Edit site Name River Ogwen WFD water body codes GB110065054160 WFD (national) typology WFD water body name Ogwen - upper Pre-project morphology Over deepened Reference morphology Pool-riffle 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 Salmonids Dominant hydrology Dominant substrate Gravel River corridor land use Agricultural (Livestock) 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) 900900 m <br />0.9 km <br />90,000 cm <br /> Project started 1998/09/01 Works started Works completed 1998/11/30 Project completed Total cost category 50 - 100 k€ Total cost (k€) 5656 k€ <br />56,000 € <br /> 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 Supplementary funding information Of the £48,000 (€56,000) project cost- £8,000 (€9,300) was spent on a flood model and £5,000 (€5,800) was spent on design. Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Flood risk management Hydromorphology Channel pattern/planform, sediment transport Biology Fish Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Installation of cascades, Creation of pools and riffles Floodplain / River corridor Planform / Channel pattern Morphology of the bed altered 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 Fish Yes Yes Yes Yes No Improvement 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 http://www.therrc.co.uk/pdf/manual/MAN 5 3.pdf Manual of River Restoration Techniques entry (RRC) http://www.therrc.co.uk/pdf/manual/MAN 8 4.pdf Manual of River Restoration Techniques entry (RRC) Supplementary Information Edit Supplementary Information