Case study:River Little Ouse at Thetford

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Location: 52° 23' 56.36" N, 0° 44' 55.03" E

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Project overview

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Status	In progress
Project web site
Themes	Flood risk management, Habitat and biodiversity
Country	England
Main contact forename	Chris
Main contact surname	Gregory
Main contact user ID
Contact organisation	British Trust for Ornithology
Contact organisation web site	http://www.bto.org/
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

Little Ouse following restoration

Project summary

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In 1991 the site and adjacent land were purchased by the BTO to create a wetland bird reserve. The Little Ouse had previously been straightened and flowed in a trapezoidal channel. In-stream habitat was poor, macrophytes were confined mainly to the shallow margins and the substrate was dominated by sand with some silt and gravel. The Environment Agency were approached to assist with restoring flows to the original, meandering course which remained as a damp depression. By restoring flows to the old channel 900m of diverse river habitat with varied morphology and a connection to the floodplain was gained. Problems have been experienced with the breaching of several banks at meanders and the development of permanently ponded areas (the original design was aimed at encouraging seasonal inundation to create suitable nesting habitats for waders such as lapwing). Several attempts have been made to repair these breaches with techniques such as blue clay banks and pre-seeded coir matting Further remediation works are planned for September 2013 and will consist of the creation of 'living revetments'. The approximate cost of this additional work is £6,000.

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Image gallery

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Reopening the meanders

Breach of meanders - 2002

Bank reinforcement - Oct 2003

Breach of reinforced bank - March 2004

Pre-seeded coir matting - Dec 2005

Erosion of coir matting - April 2008

Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name River Little Ouse at Thetford WFD water body codes GB105033043090 WFD (national) typology WFD water body name Pre-project morphology Artificial channel, Straightened, trapezoidal Reference morphology Sinuous meander 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 Wading birds (e.g. Lapwing) Dominant hydrology Dominant substrate Gravel River corridor land use Agriculture (arable) 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 1994/04/01 Works started Works completed Project completed 1994/07/01 Total cost category 10 - 50 k€ Total cost (k€) 17.317.3 k€ <br />17,300 € <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 Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Restore floodplain connectivity Hydromorphology Width & depth variation, Channel pattern/planform Biology Invertebrates, Macrophytes Physico-chemical Other reasons for the project Creation of wetland area for wading birds Measures Edit Measures Structural measures Bank/bed modifications Creation of pools and riffles Floodplain / River corridor Creation of backwater and ponds, New habitats construction, Reconnect and restore historic aquatic habitats Planform / Channel pattern Re-connect old 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 Width & depth variation No Yes Yes No No Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Invertebrates: Diversity No Yes No Yes No Improvement Macrophytes No Yes Yes No No Deterioration 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 1 7.pdf RRC Manual of River Restoration Techniques entry Supplementary Information Edit Supplementary Information