Case study:Harbertonford Flood Alleviation Scheme
To discuss or comment on this case study, please use the discussion page.
- 1 Project overview
- 2 Image gallery
- 3 Catchment and subcatchment
- 4 Site
- 5 Project background
- 6 Reasons for river restoration
- 7 Measures
- 8 Monitoring
- 9 Additional documents and videos
- 10 Additional links and references
- 11 Supplementary Information
|Project web site|
|Themes||Flood risk management, Social benefits|
|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 & Harbertonford Parish Council|
|Parent multi-site project|
| This is a parent project
encompassing the following
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, the Environment Agency, South Hams District Council and Harbertonford Parish Council, costing £2.6 million. Its aim 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.
As part of the bed-lowering technique, a series of pool-riffle sequences were constructed within the channel through Harbertonford - a best practice approach for habitat enhancement, proposed by the River Restoration Centre (www.therrc.co.uk). These would provide both improved spawning habitat and habitat for adult fish.
- Channel lowered by 600mm through Harbertonford using pool-riffle sequences, to increase channel capacity, to withstand 28 cumec flow (1:10 year event). Also widened in areas to further increase capacity. Two weirs lowered to minimise backwater effect (Crowdy Mill and Mill Leat).
- Zoned clay-core embankment dam constructed 2km US of Harbertonford, with 4.1 ha flood storage reservoir (150, 000 cu. metre capacity), capable of withstanding up to 1:40 year event.
- Flood wall installed along a portion of the river, through Harbertonford. Replaced earth bank. Surface drainage systems improved.
Community Involvement - Local primary school visited site during construction of dam and have continued to visit 'reservoir' site, to study ecological development.
Monitoring surveys and results
Catchment and subcatchment
Select a catchment/subcatchment
Cost for project phases
Reasons for river restoration
Hydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Additional documents and videos