Medmerry is located in a low lying area between the communities of Selsey and Bracklesham on the western side of the Manhood coastal peninsula, approximately 10km south of Chichester in West Sussex. Medmerry has long faced problems with flooding from the sea, with regular breaches of the shingle bank, most recently in 2008, when over £5m of damage was caused. The solution was managed realignment where new defences are built inland from the coast, the existing defence, the shingle bank, is breached and a new intertidal area is allowed to form seaward of the new defences.
The completed scheme is the largest managed realignment of the open coast in Europe, and the first in the UK on the stretch of coast most threatened by coastal flooding. It has been recognised locally,nationally and internationally as an exemplar project. The scheme has significantly reduced the risk of coastal flooding to the residents of Selsey and the surrounding communities, whilst also providing more than 180 hectares of important new intertidal habitat, providing compensation for losses in the Solent as a result of rising sea levels. Mitigation areas of freshwater and terrestrial habitats have also been created. It has incorporated extensive public access, created economic growth opportunities and realised maintenance savings of £300,000 per annum.
The Environment Agency is responsible for managing the coastal frontage, inland drainage channels and associated structures for the Medmerry area. In 2009 they appointed Jacobs as principal designer to deliver a coastal flood alleviation scheme for the Medmerry area, from initial assessment through to detailed design and construction supervision; including undertaking a statutory Environmental Impact Assessment and obtaining planning consent.
The environmental design was co-ordinated by the Environment Agency NEAS team. This included a landscape brief to restore a historic wetland landscape and meet the following objectives:
– To create an innovative, safe and sustainable site with a naturalistic character, exceptionally rich in wildlife and natural beauty, inspiring for people while functioning as a natural coastal zone and flood defence
– To design the site so it can be constructed in a cost effective way that minimises environmental impact, engages the community and responds to the challenges of climate change
– To create a regional exemplar of a multi-functional coastal site
The principle element of the scheme is a new 7km flood embankment, parts of which are almost 2km inland from the open sea, which is tied into the existing shingle ridge at its seaward extents by two rock armour revetments at the eastern and western extent of the scheme. 100% of excavated material was reused on site to construct the embankment and additional viewpoints. With the new flood embankments in place a breach was made in the existing flood defence, the shingle beach, in September 2013.
Local communities were concerned about their vulnerability to coastal flooding and addressing these concerns was essential to successful completion of the scheme. To reflect the multiple needs of the scheme, the project team worked with stakeholders to agree three broad objectives which remained throughout development and construction:
– Sustainable flood and coastal erosion management
– Maximise intertidal and freshwater habitat creation
– Community involvement
Working in partnership with the RSPB from the earliest stages was key to the success of the project, and maximised habitat delivery, ensuring that it was fully integrated with the engineering design and scheme construction. The scheme has created a 400ha mosaic of naturally functioning and developing intertidal, freshwater and terrestrial habitats. Of this around 183ha will develop as intertidal habitat including saltmarsh, mudflat, saline lagoons and transitional grasslands, which will protect the regional integrity of Natura 2000 habitats in and around the Solent. Additional freshwater and terrestrial habitat have been created, which will enhance the conservation status of UK priority habitats and species. Key habitats are ponds, coastal flood plain grazing marsh, fen, lowland meadow and reedbed. The habitats are designed to be resilient to climate change so that they are sustainable long term, and will also contribute to the achievement of Biodiversity 2020 targets. The originally intensively managed arable farmland is now converted to low intensity mixed farmland around the perimeter of the scheme and will be sensitively managed for vulnerable farmland bird species.
Medmerry also provides a major boost for green tourism and is under the management of the RSPB as a nature reserve, providing access, education and volunteering opportunities. It provides for improved public health associated with access to the countryside and wildlife and additional growth has been brought to the area by allowing businesses to operate all year round without the risk of flooding.
