Medmerry managed realignment

Medmerry managed realignment
Name	Medmerry managed realignment
Location	Selsey, West Sussex, England
Coordinates	50.792°N -0.793°W
Status	Completed
Began	2011
Completed	2013
Owner	Environment Agency
Type	Coastal realignment
Cost	£28 million

Medmerry managed realignment is a coastal realignment project on the south coast of England near Selsey, West Sussex, implemented to reduce flood risk and restore intertidal habitat. The scheme converted agricultural land into a new saltmarsh by breaching existing sea defences, creating a large managed realignment site designed to work with natural processes. It was led by the Environment Agency and involved multiple partners, contractors, and stakeholders from local authorities and conservation organisations.

Background and Rationale

The project responded to repeated tidal inundation events and erosion on the English Channel frontage affecting towns such as Selsey, Chichester, and infrastructure serving West Sussex County Council. National policy drivers included guidance from the Environment Agency and planning frameworks influenced by documents from Department for Environment, Food and Rural Affairs and national strategies for shoreline management. The scheme formed part of the shoreline management plan for the Sussex coast and reflected principles found in managed realignment precedents like Kniepsand, Wallasea Island and Pagham Harbour restorations. Financial pressures and technical assessments by consultancies linked to firms working for Arup and other engineering consultancies supported a long-term, sustainable defence option over continuous hard engineering, with policy context influenced by European directives such as the Habitats Directive and national flood risk legislation.

Planning and Design

Design development involved multi-disciplinary input from coastal engineers, ecologists, and planners including teams associated with Royal HaskoningDHV, Mott MacDonald, and the Environment Agency. The approved scheme established a new earth embankment set back from the original frontage, a controlled breach location, and a new tidal gate layout to allow tidal inundation, reflecting techniques documented in case studies like Essex estuaries and Norfolk coast projects. Environmental impact assessments engaged statutory consultees including Natural England, RSPB, and local authorities such as Chichester District Council. Funding arrangements combined public funding from Department for Environment, Food and Rural Affairs and regional allocations coordinated with planning consents and habitat compensation measures tied to European and domestic conservation obligations.

Construction and Engineering

Construction contractors employed heavy earthmoving plant to construct the setback embankment, realign drainage channels, and create control structures drawing on experience from coastal projects at Humber Estuary and Thames Estuary. Techniques included rock revetment placement, clay core embankments, and construction sequencing to maintain access to utilities and roads managed by West Sussex County Council. Project management overlapped with standards used by large infrastructure contractors such as Balfour Beatty and civil engineering practices common to projects associated with Highways England. The breaching operation was carefully timed around tidal cycles and biological windows advised by Natural England and ecologists, and navigation considerations were coordinated with the Maritime and Coastguard Agency.

Environmental and Ecological Impacts

Ecological outcomes aimed to create intertidal saltmarsh, mudflat, and associated coastal grassland habitats benefitting species recorded by conservation groups including RSPB, Sussex Wildlife Trust, and British Trust for Ornithology. Monitoring has documented colonisation by estuarine invertebrates, wading birds known from Slimbridge and Cley Marshes analogues, and saltmarsh vegetation comparable to protected sites like Chichester Harbour. The project provided compensatory habitat relevant to obligations under the Habitats Directive and enhanced biodiversity networks advocated by Natural England and landscape-scale initiatives tied to the South Downs National Park Authority. Some stakeholder concerns referenced potential impacts on agricultural interests and cultural heritage recorded by Historic England, requiring mitigation measures and compensation.

Flood Risk Management and Coastal Defence Outcomes

The scheme reduced overtopping and flood risk for nearby communities by replacing vulnerable frontal defences with a more sustainable, strategically set-back embankment, contributing to flood resilience for settlements including Selsey and facilities managed by Chichester District Council. Hydrodynamic modelling used methods common to studies of the North Sea and English Channel coasts, and outcomes aligned with national resilience aims promoted by Cabinet Office guidance on emergency planning. Cost–benefit analyses compared long-term maintenance liabilities against alternatives, showing lower lifecycle costs consistent with other managed realignment projects such as Wallasea Island. The project also altered local wave and sediment regimes, with monitoring coordinated with university groups experienced in coastal geomorphology at institutions like University of Southampton and University of Portsmouth.

Community Engagement and Socioeconomic Effects

Engagement processes included public consultations with parish councils, local landowners, and organisations such as Selsey Town Council, Chichester District Council, and voluntary groups. Economic effects touched on agricultural compensation, recreational opportunities, and tourism patterns linked to birdwatching networks associated with RSPB and ornithological societies like the British Trust for Ornithology. Local media coverage involved outlets such as the Chichester Observer. Educational partnerships with regional schools and higher education institutions including University of Sussex promoted community science and interpretation at visitor facilities supported by conservation charities and local authorities.

Monitoring, Maintenance, and Adaptive Management

Long-term monitoring programmes coordinate agencies and research institutions including Natural England, the Environment Agency, and academic partners to track geomorphology, habitat development, and bird populations with methods comparable to monitoring at Exminster Marshes and Hollingworth Lake. Maintenance of the setback embankment, drainage infrastructure, and visitor access is managed by local authorities and contractors following adaptive management plans informed by periodic reviews and contingency arrangements similar to protocols used by Marshland management projects. Ongoing adaptive responses address sea-level rise scenarios discussed in national science assessments from bodies such as the Met Office and inform updates to regional shoreline management plans.

Category:Coastal management in England