Case study:Long Eau (Great Eau)

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Location: 53° 21' 22.58" N, 0° 6' 55.08" E

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Project overview

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Status	Complete
Project web site
Themes	Flood risk management, Habitat and biodiversity, Land use management - agriculture
Country	England
Main contact forename	Nick
Main contact surname	Elbourne
Main contact user ID
Contact organisation	Lincolnshire Chalk Streams
Contact organisation web site	http://www.lincswolds.org.uk/chalk-streams/lincolnshire-chalk-streams
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

Long Eau floodplain 2005

Project summary

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Flowing from the Lincolnshire Wolds to the North Sea, the Long Eau drains a small catchment of 22.3 km2, but together with the Great Eau has a catchment area of 112.3 km2. Before restoration, the river had become embanked and channelised to protect adjacent agricultural land from flooding. The flood banks were steeply sloped directly into the channel. Dredging and removal of bankside vegetation was part of the maintenance regime, which had removed morphological features, in channel habitats and natural substrate. Historically the Long Eau had a history of washlands, regularly flooding the land adjacent to the river. Three sites were chosen along the Little ands Great Eau to demonstrate the relocation of flood banks and the provision of flood storage areas on neighbouring land. A secondary objective was to enhance habitats. An environmental stewardship scheme offered a ten year grant scheme to farmers/landowners, some of whom were already supportive of the idea of nature conservation. Long Eau at Manby- Left floodbank was lowered to just above ground level. The adjacent field was widened and flattened to act as an over spill area (1 in 10 slope). Material generated from embankment removal was used to infill and Internal Drainage Board drain which ran through flood storage area. This drain was re located behind the new embankment to maintain land drainage. The new embankment slopes were 3:1 to a height of 2.5-2.7 meters. Ledges and berms were created along the channel to increased habitat potential. Performance 1995-2001- Since completion flood protection has increased, as water spills onto new floodplain when channel reaches 2.6m or above. Below this level 75% of floodplain will retain water up to 0.5m for up to 4 months. This provides an important habitat for wetland birds. Lapwing and redshank have bred at the site. The Environment Agency estimates a saving of £400-500 a year on the previous maintenance regime.

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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 Witham Subcatchment River name Long Eau Area category 10 - 100 km² Area (km2) Maximum altitude category 100 - 200 m Maximum altitude (m) 110110 m <br />0.11 km <br />11,000 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Arable and Horticulture Waterbody ID GB105029061670 Site Edit site Name Long Eau at Manby WFD water body codes GB105029061670 WFD (national) typology WFD water body name Long Eau Pre-project morphology Embanked, Over-widened, Over deepened Reference morphology Set back defence 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 Artificially regulated Dominant substrate River corridor land use Intensive agriculture (arable), 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) 900900 m <br />0.9 km <br />90,000 cm <br /> Project started 1992 Works started 1995/05/01 Works completed 1995/07/01 Project completed 1996/01/01 Total cost category 50 - 100 k€ Total cost (k€) Benefit to cost ratio Funding sources environmental stewardship scheme 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 50 - 100 k€ Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Flood risk management Hydromorphology Biology Physico-chemical Other reasons for the project secondary objective of habitat improvement Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Displacement of flood defences, Lowering of embankments Planform / Channel pattern Creation of backwater 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 Supplementary Information Edit Supplementary Information