Case study:River Little Ouse at Thetford

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Location: 52° 23' 56", 0° 44' 55"
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Project overview

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Status Complete
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.

Monitoring surveys and results

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Lessons learnt

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Image gallery


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
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Catchment and subcatchment

Catchment

River basin district Anglian
River basin Cam and Ely Ouse (including South Level)

Subcatchment

River name Little Ouse River
Area category 100 - 1000 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 68
68 m
0.068 km
6,800 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB105033043400



Site

Name River Little Ouse at Thetford
WFD water body codes GB105033043090
WFD (national) typology
WFD water body name Little Ouse
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

Reach length directly affected (m) 900
900 m
0.9 km
90,000 cm
Project started 1994/04/01
Works started
Works completed
Project completed 1994/07/01
Total cost category 10 - 50 k€
Total cost (k€) 17.3
17.3 k€
17,300 €
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

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

Structural measures
Bank/bed modifications Creation of pools and riffles
Floodplain / River corridor Creation of backwaters, Habitat creation, Habitat restoration, Creation of pond
Planform / Channel pattern Reconnection of cutoff meander
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other


Monitoring

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

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

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



Additional documents and videos


Additional 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

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