Case study:Great Ryburgh End Restoration Scheme

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Location: 52° 48' 16.25" N, 0° 54' 45.19" E

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity, Hydromorphology
Country	England
Main contact forename	Adam
Main contact surname	Thurtle
Main contact user ID	User:Rdryden
Contact organisation	Environment Agency
Contact organisation web site	http://www.environment-agency.gov.uk
Partner organisations	Natural England, Water Management Alliance
Parent multi-site project	Case_study:Wensum River Restoration Strategy
This is a parent project encompassing the following projects	No

Vegetated berm and woody debris creating flow and habitat diversity within link channel – August 2013. Photo credit RRC

Project summary

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The restored reach at Great Ryburgh extends between Great Ryburgh Mill and Sennowe Bridge. A significant length of meandering river channel was completely bypassed by a straightened channel sometime in the mid nineteenth century. The engineered channel was over deep, isolated from the floodplain and lacked both flow and habitat diversity. A feasibility study indicated that the reconnection of 1100m of the original course would significantly improve the ecology and natural functioning of the SSSI and SAC.

A key part of the restoration was to reinstate the original course by plugging the straightened channel and creating a new link to the original course at the upstream end. The height of the plug was set so that it can be overtopped during high flows and functions as an overflow channel. The new link channel was designed to restore some of the geomorphological function lost when the channel was straightened. The downstream end of the straightened channel has been left open to create an ecologically valuable backwater. Although disconnected, the line of the original channel remained and mature alder and willow were evident in places along the margins. The old channel was excavated to match natural geomorphological features as much as possible. Where riverbed gravels were found they were left intact, and supplemented in some areas to create shallow glides.

Deeper pools were dug on the outer bends of meanders and lateral berms and woody debris were installed to increase sinuosity. Backwaters and bays have also been created along the channel to provide fish refuge and additional habitat. Native shrubs and trees, predominantly willow and alder, have been selectively planted to create riparian shade and these have been fenced to protect them from grazing livestock.

Monitoring surveys and results

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2013's post-restoration electro-fishing survey recorded 705 fish representing 12 species, an increase from the 107 fish of 7 species caught in 2012 when the habitat was still quite bare following restoration. These figures compare with 158 fish of 9 caught in a pre-restoration survey in an immediately adjacent reach. Fish density in the restoration site in 2013 was 11.7 individuals per 100m² compared with 5.7 per 100m² in the pre-restoration survey site. Standing crop was 568 grams per 100m² in the restoration site, a small increase on the 508 grams per 100m² recorded during the pre-restoration survey. Numbers of stone loach, bullhead, brook lamprey, brown trout, dace and gudgeon have increased compared with the pre-restoration conditions. Further monitoring will be undertaken in future years to understand more about how fish populations change in response to habitat improvements.

The low level shelves created at summer water level at the channel margins have been colonised by a diverse flora including water mint, water forget-me-not, brooklime and gipsywort. The river channel itself supports a number of typical chalk stream plant species including watercress, water starwort, lesser water-parsnip and whorl-grass.

Lessons learnt

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The in-channel works have been successful and flow diversity and sinuosity has been achieved. The lateral berms and woody debris have vegetated quickly, providing physical habitat and creating additional flow diversity. Marginal vegetation is well established and the banks support an extremely diverse range of species. The planted trees are growing well and several self-seeded trees, predominantly alder, are establishing along the banks.

The new backwaters hold an abundance of fish fry, and trout were observed resting in the pools. In addition, a kingfisher and otter spraint and prints were sighted during the RRC visit. Ecological surveys were carried out in August 2013 and the results of these will determine the extent of ecological recovery following the works. Some adaptive management of the upstream end of the plug has been undertaken. Locally sourced turfs have been used to reinforce the plug and reduce erosion during high flows. Some cattle poaching has occurred at the upstream end of the reinstated channel, and although action is not currently necessary, this will continue to be monitored by the Environment Agency.

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 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: Meander reinstatement on the River Wensum at the Ryburgh Loop, 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 WFD water body codes GB105034055881 WFD (national) typology WFD water body name 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 No 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) 13201,320 m <br />1.32 km <br />132,000 cm <br /> Project started Works started 2011/09/01 Works completed 2011/12/31 Project completed Total cost category 100 - 500 k€ Total cost (k€) 150150 k€ <br />150,000 € <br /> Benefit to cost ratio Funding sources Environment Agency 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 Land drainage, Impoundments (not hydropower) Hydromorphology Quantity & dynamics of flow, Width & depth variation Biology Fish Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Diversification of in-channel features, Soft erosion solutions, Introducing large woody debris Floodplain / River corridor Tree planting, Creation of backwaters 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 http://www.wensumalliance.org.uk/newsletters/RWRSnewsletter dec11.pdf River Wensum Restoration Strategy Newsletter Issue 8 December 2011 http://www.therrc.co.uk/pdata/pdfs/p1908.pdf RRC case study - Great Ryburgh End Restoration Scheme Supplementary Information Edit Supplementary Information