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ABPmer
Quayside Suite
Medina Chambers
Town Quay
Southampton
SO14 2AQ
2013
Managed realignment
United Kingdom
Sussex Coast (Sussex)
-0.8244
50.751
Lagoon
Mudflat
Reedbed
Saltmarsh
Transitional Grassland
Extra habitat landward of seawall (including 6km of new water vole ditch to landward)
302 Hectares
Compensation
Flood Risk Management
Reduce Flood Protection Costs
Create a More Natural Shoreline
Provide a Recreational Facility
The Medmerry Realignment is an innovative and large-scale coastal management project. It is the only open-coast managed realignment in the UK and remains (as of January 2020) the only such project to involve deliberately creating a breach through a mobile shingle barrier.
This project was carried out by the Environment Agency (England) in 2012 and 2013 to provide coastal flood protection and to create a large expanse of coastal habitat.
The design included the following:
1) A new 7 km long embankment at the back of the site (up to 2.5 km from the seafront)
2) A network of ponds and ditches behind the embankment to provide a flood storage and drainage function as well as to create valuable freshwater wetlands (including mitigation areas for protected water vole and reptiles)
3) A 300 hectare (ha) area of new coastal habitat and farmland in front of the embankment (i.e. on seaward facing side) which was designed to include:
3a) Around 183 ha of lower lying intertidal habitat that is regularly inundated by the tide
3b) Around 117 ha of higher elevation land that does not get inundated by the tide and includes a mix of transitional grassland and areas used for grazing and agriculture
4) Four sluice structures within the embankment to allow freshwater to drain into the main site and out to coastal waters when required
5) Preparatory landscaping and channel excavations in front of the embankment to facilitate freshwater drainage and ensure tidal waters efficiently flood and ebb over the new intertidal areas (which also helps to maximise the amount of intertidal habitat created).
As one of the final key stages of the project’s implementation, the shingle barrier fronting the site was breached on 9 September 2013. This allowed tidal waters to inundate the lower lying areas within the site and create large expanses of new intertidal habitat in front of the new flood embankment.
The shingle barrier had previously been mobile and required regular (typically annual) reshaping to minimise the risk of coastal flooding.
The breach in this barrier was 110 m wide and included a 30 m wide deeper central inlet channel (at a depth equivalent Mean Low Water Neap (MLWN) tide level).
This project has provided valuable lessons about working with nature and about engaging with and involving local communities in coastal management decisions.
ABPmer
Quayside Suite
Medina Chambers
Town Quay
Southampton
SO14 2AQ