Case study:Harbertonford Flood Alleviation Scheme

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Location: 50° 23' 27.36" N, 3° 43' 19.76" W

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Project overview

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Status	Complete
Project web site
Themes	Flood risk management, Social benefits
Country	England
Main contact forename	Nick
Main contact surname	Elbourne
Main contact user ID	User:NickRRC
Contact organisation	River Restoration Centre
Contact organisation web site
Partner organisations	Environment Agency, DEFRA, South Hams District Council and Harbertonford Parish Council.
Parent multi-site project
This is a parent project encompassing the following projects	No

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Project summary

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The River Harbourne flows through the village of Harbertonford, which has been flooded on 21 separate occasions over the past 60 years - of which 6 flood events occurred between 1998 and 2000. The catchment is highly 'flashy', with little warning for residents prior to a flood.

The Harbertonford Flood Alleviation Scheme was a joint project funded by DEFRA and the Environment Agency, costing £2.6 million. The primary aim of the project was to reduce the risk of flooding through the implementation of engineered flood alleviation solutions. A zoned clay-core embankment dam ('Palmer's Dam') with a 4.1 ha (150,000 cu m) reservoir storage area was constructed 2km upstream of Harbertonford, in conjunction with 600mm of bed level lowering and channel widening through Harbertonford to increase channel capacity (to accommodate flows up to 28 cumecs - 10 year flood. A flow control system was installed at the reservoir outlet to permit normal river flow, with automated flood control gates to throttle flows during a flood event. In addition, a flood defence wall was installed and surface drainage systems improved. Together, these measures were built to prevent flooding in Harbertonford up to a 1 in 40 year flood event.

On 7th July 2012, a 1 in 40 year flood event occurred and Palmer's Dam was overtopped for the first time since its construction. This resulted in the flooding of some properties in Harbertonford, however flooding was limited to a few lowlying homes and the flood peak was significantly delayed, giving increased warning time.

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Catchment and subcatchment

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Site

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Name	Harbourne at Harbertonford
WFD water body codes	GB108046005170
WFD (national) typology	Low, Small, Siliceous
WFD water body name	Harbourne River
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	Slate/shale, overlain by alluvium.
River corridor land use	Agriculture.
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Average bankfull channel width (m)
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Project background

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Reach length directly affected (m)
Project started
Works started
Works completed	2002/09/01
Project completed
Total cost category	more than 10000 k€
Total cost (k€)	35000003,500,000 k€ <br />3,500,000,000 € <br />
Benefit to cost ratio
Funding sources	DEFRA, South Hams District Council, Harbertonford Parish Council

Cost for project phases

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Reasons for river restoration

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Mitigation of a pressure	Flood risk management
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Measures

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Monitoring

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Monitoring documents

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Additional links and references

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Link	Description
http://ec.europa.eu/ourcoast/download.cfm?fileID=950	Environment Agency - 'Harnessing the Harbourne'
http://harbertonford.org/index.php/Local/HowItWorks	Harbertonford News

Supplementary Information

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