Case study:Meander reinstatement on the River Wensum at the Ryburgh Loop

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Location: 52° 48' 11.48" N, 0° 55' 7.97" E

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Project overview

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Status	Complete
Project web site	http://www.therrc.co.uk/rrc_case_studies1.php?csid=76
Themes	Fisheries, Habitat and biodiversity
Country	England
Main contact forename	Rob
Main contact surname	Dryden
Main contact user ID
Contact organisation	Environment Agency
Contact organisation web site	http://www.environment-agency.gov.uk
Partner organisations	Wensum River Restoration Strategy
Parent multi-site project	Case_study:Wensum River Restoration Strategy
This is a parent project encompassing the following projects	No

The reconnected meander - the Ryburgh Loop

Project summary

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Site background The River Wensum is a chalk SSSI and SAC river currently stated as being in unfavourable condition. Located to the southeast of the Norfolk town of Fakenham the meander loop at Great Ryburgh Common was bypassed in the 1950’s when the River Wensum was straightened, widened and deepened as part of a land drainage improvement scheme.

The river restoration work undertaken involved reinstating a former meander, increasing channel sinuosity and flow diversity. The work was part of the wider River Wensum Restoration Project.

Objectives To re-instate the natural river form and function by re-connecting the old meander. It was designed so that at normal flows all the flow would go down the old meander and at high flow, part of the flow would be diverted into the straightened channel. To re-connect the old meander by removing the silt layer from the old channel whilst retaining the existing gravel substrate where it still existed.

Design The old meander was carefully excavated leaving the riverbed gravels intact where they already existed. In addition new gravels were added to create shallow glides. Deeper pools were dug to provide refuge ares for fish and other aquatic species. The existing straightened channel was plugged such that in normal flow conditions, the river flows around the re-connected meander. The straightened channel therefore acts as a flood relief channel at times of high flow and as a quiet backwater during normal flow. In addition, channel narrowing was achieved by creating a bund along the line of the new bank, and this was covered with coir matting and was planted up with live plants.

Subsequent performance – RRC’s views (2011) Eighteen months on, the site is fully vegetated and functioning well as a re-connected meander. The original gravel bed was exposed during excavation and the use of adaptive management allowed these original features to be incorporated into the on-the-ground works. The Environment Agency OPS team was used to do the works as they had experience of doing similar work(at Bintree further down the catchment). Prior to re-meandering, the channel was straightened and over-wide. The project has recreated the natural chalkstream habitat, with pool and riffle sequences. The substrate now has macrophytes growing along much of its length. By allowing high flows to pass down the old straightened channel the flood capacity has been increased, and during normal flows the old straightened channel acts as a backwater habitat.

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Ryburgh Common pre works

Ryburgh Common pre-works

Ryburgh Common before works

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district Anglian River basin Broadland Rivers Subcatchment River name Wensum US Norwich Area category 100 - 1000 km² Area (km2) Maximum altitude category Less than 100 m Maximum altitude (m) 9898 m <br />0.098 km <br />9,800 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Arable and Horticulture Waterbody ID GB105034055881 Other case studies in this subcatchment: Great Ryburgh End Restoration Scheme, River Wensum Restoration, Reach 10 Lenwade, River Wensum Restoration, Reach 3a Costessey, River Wensum Restoration, Reach 9 Attlebridge, River rehabilitation on the River Wensum at Swanton Morley, Sculthorpe Moor Restoration Scheme, Wensum River Restoration and Floodplain Enhancement, Wensum River Restoration and Floodplain Enhancement, Pensthorpe Site Edit site Name Ryburgh Loop WFD water body codes GB105034055881 WFD (national) typology WFD water body name River Wensum Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body No National/international site designation EU - Special Area of Conservation Local/regional site designations UK - Site of Special Scientific Interest Protected species present Yes Invasive species present No Species of interest Dominant hydrology Dominant substrate River corridor land use Improved/semi-improved grassland/pasture 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) 600600 m <br />0.6 km <br />60,000 cm <br /> Project started 2010/10/01 Works started Works completed Project completed 2010/12/31 Total cost category 1 - 10 k€ Total cost (k€) 10.510.5 k€ <br />10,500 € <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 paid in pound 105,000 Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Hydromorphology Channel pattern/planform Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern Reconnection of cutoff meander 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 Great Ryburgh Fact Sheet 2 Great Ryburgh Fact Sheet 1 Additional links and references Edit links and references Link Description http://www.therrc.co.uk/rrc case studies1.php?csid=76 RRC case study Supplementary Information Edit Supplementary Information