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Medmerry Managed Realignment – sustainable coastal
management to gain multiple benefits
Environment Agency, Worthing, UK.
Introduction
Construction of the managed realignment scheme at Medmerry is planned to start at the end
of 2011. Coastal realignment has been recommended for this area by both the wide scale
shoreline management plan and the locally focused coastal flood and erosion risk
management strategy. The scheme will both reduce the very significant flood risk for the
local area and create new intertidal habitat to offset losses across the shoreline of the northern
Solent. The urgency to meet both these requirements has driven a tight programme to design
the scheme in outline and gain the major approvals needed for construction of the scheme.
Involvement of local people and groups has been an essential part of designing the
realignment scheme. By including representatives of existing community networks and non
government organisations from the start of the project, their interests were included in
decisions as they were made. This helped gain local support for the Environment Agency’s
proposals and show the real stake that there was for everyone in meeting all of the objectives
of the scheme. Local representatives have accepted the part that the realignment needs to
play in adaptation to secure the long term future for their area. Locally driven groups have
begun to draw up plans for enhancements beyond the scheme to maximise the opportunities
for recreation and access network enhancements in the area.
Location
Medmerry is on the western side of the coastal peninsula approximately 10km south of
Chichester on the south coast of England. The coastline borders the Solent facing towards
the Isle of Wight. The land area is mainly agricultural, with widely spaced small villages
and hamlets. To the west and the east of the site are 2 caravan parks; the Sussex Beach
Holiday Village and Bunn Leisure respectively (Figure 1). Low lying land extends towards
the sole access road to the town of Selsey and the edge of Pagham Harbour 3km inland. The
foreshore and 50 hectares of land adjacent to the defence at Medmerry is designated a Site of
Special Scientific Interest (SSSI), owned and maintained as a nature reserve by the RSPB.
Background
The Environment Agency currently manages coastal defences, inland drainage channels and
associated structures for the area. Defences are formed of two raised shingle banks, separated
by an area of higher ground where the Bunn Leisure holiday park business is located.
Maintaining the defences requires constant work throughout each winter to recycle and reprofile the shingle between tides. Despite this work, storms have caused the bank to breach
14 times since 1994 causing flooding to agricultural land, homes and holiday parks. Around
350 homes and businesses are at risk from coastal floods in addition to thousands of fixed
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caravans and holiday chalets. The sole access road and utilities serving the community of
5,000 households in Selsey are at risk from coastal flooding.
Strategic Issues
Managed realignment at Medmerry is seen as important in long term management of flood
and erosion risk by both the wide scale shoreline management plan and the more local flood
and erosion risk management strategy.
Coastal flood and erosion risk for the coastal peninsula around Medmerry was considered in
the Pagham to East Head Coastal Defence Strategy, (henceforth referred to as the strategy)
completed in 2009. Studies concluded that existing shingle defences are unable to prevent
flooding now and will not remain effective beyond the short term. Implementation of an
alternative way of managing coastal flood risk is needed as soon as possible. Following
appraisal of available options, managed realignment was recommended. New inland
embankments were proposed to be built largely from locally sourced earth and clay, with a
tidal breach allowed to form along the existing coastline.
The strategy recognised the potential for the formation of new intertidal habitat as part of the
realignment but did not include plans to actively form new intertidal areas or secure their
future. Economic appraisal had included evaluation of environmental benefits of creating
new intertidal habitat, contributing approximately 15% to the total economic benefits.
Calculations were based on latest available guidance which makes use of research on already
completed realignments. The strategy recognised that a realignment scheme based only on
managing flood risk for the local area would be unlikely to gain funding and would attract
strong opposition.
The North Solent Shoreline Management Plan (SMP) completed in 2010, assessed issues on a
wider scale for the coastline stretching some 70km westwards from Medmerry. Natural
harbours within the Solent host 4,750 hectares of intertidal habitat that form part of the
Natura 2000 network. The Solent Coastal Habitat Management Plan (2003) reported 100
hectares of intertidal habitat loss across the Solent. The Solent Dynamic Coast Project (2008)
produced for the SMP, confirmed these losses and also estimated that there will be a loss of
600 hectares over the next 100 years through coastal squeeze caused by rising sea levels.
New intertidal habitat is needed to restore the losses already experienced and to offset coastal
squeeze effects from maintaining and renewing existing coastal defences across the northern
Solent. The SMP was completed after the strategy, confirming the managed realignment
recommendation at Medmerry, recognising the importance of the site in creating new
intertidal habitat.
To ensure that legal obligations for protection of habitats and species will be met, while still
allowing protection for people and property, the Environment Agency established the
Regional Habitat Creation Programme (RHCP). In order to take advantage of the opportunity
at Medmerry, following the findings of the Solent Dynamic Coast Project, three farms were
purchased by the Environment Agency at Medmerry. This land, together with the SSSI area
already owned and run as reserve by RSPB, formed the core of the proposed realignment
scheme.
During the production of the strategy, extensive public engagement work was undertaken.
Initially, many people would have preferred an option to hold the line of the existing coast.
They felt that this would provide a better flood defence than managed realignment could.
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The Environment Agency worked with local communities to facilitate a greater
understanding about how managed realignment works and how it was chosen as the preferred
option for managing coastal flood risk at Medmerry. Experience during the development of
the Pagham to East Head strategy and from other managed realignment schemes elsewhere
showed that ongoing support and involvement of local stakeholders would be essential in
promoting the scheme to gain permits and approvals needed for its construction. Many people
still view managed realignment as a lesser option for managing flood risk as it brings the sea
closer to their properties.
One aspect of the strategy which had given rise to particular concern locally, was the impact
on the Bunn Leisure holiday parks situated on low ground stretching inland from the coast at
Medmerry. The line of new defences recommended by the strategy at Medmerry extended
through part of the holiday park. Unless other action could be taken, this would result in the
loss of caravan pitches in areas seaward of the proposed alignment. Bunn Leisure responded
by developing plans to safeguard the future of their site by designing and gaining planning
permission to build their own coastal defences to protect one kilometre of the coast. The
project team has worked with Bunn Leisure in designing the realignment scheme to take
account of the construction and operation of both sets of works.
Scheme Objectives
Appraisal of the realignment scheme began immediately after completion of the strategy.
There was a priority to move quickly to reduce flood risk for the local area, create the new
intertidal habitat and keep the momentum built up by working with local people. Three
objectives were defined to address the separate requirements in implementing the managed
realignment.
 To provide a sustainable flood and coastal erosion risk management scheme with
appropriate standard of protection as cost effectively, quickly and safely as possible.
 Maximise (greatest extent) intertidal habitat and optimise (best use)
freshwater/Biodiversity Action Plan (BAP) habitat on the remainder of the Scheme
area making best use of existing topography taking climate change into account, and;
 Encourage participation during development of the scheme to deliver a product which
can be supported by local people.
The objectives were initially drawn up by the project team and amended following
workshops with others to ensure that the concerns of all stakeholders were adequately
represented.
Designing the Scheme
In designing the scheme, the challenge was to bring the three project objectives together in
order to deliver the habitat and reduce flood risk as soon as possible. Three separate groups
were formed, to work in parallel in defining scheme requirements and details.
 The core team.
 Habitat creation group.
 A Medmerry Stakeholder Advisory Group (MStAG) formed to provide the focus for
engagement with local communities.
The scheme required planning permission, and was subject to an Environmental Impact
Assessment (EIA). It was essential that the Three groups worked together in order to develop
a scheme design that would meet the objectives, and also be acceptable to the planning
authority and local people.
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The core team included engineers, environmental scientists and engagement specialists from
the Environment Agency. Specialist consultants joined the team to complete the
environmental and technical appraisal for the scheme and lead the engagement with MStAG.
The habitat creation group included Natural England, RSPB, local wildlife groups, academics
and local authority officers working with Environment Agency and consultant staff.
The ‘Medmerry stakeholder advisory group’ (MStAG) was established so that all community
groups with an interest in the scheme could be represented in its development. Membership
was limited to a workable number of 20 representatives selected by attendees at an initial
meeting of a much larger group representing local organisations and interested parties.
MStAG meetings were facilitated by specialist engagement consultants who ensured that the
members of the group could see how their issues were included in designing the scheme.
All three of the groups played an essential part in the design process, and development of the
scheme business case and planning application. Each of them fed into the definition of a
number of options to meet project objectives, and helped identify constraints and
opportunities associated with each option.
Constraints and opportunities
Design decisions were influenced by key constraints and opportunities at the site which
covered all three aspects of the scheme objectives:
 Locating the new inland embankments for cost effective flood risk management and
to maximise habitat creation opportunities.
 Determining whether the breach should be engineered or allowed to occur naturally.
Consideration also included whether one or more breaches would work best and
where along the frontage a breach would best be constructed.
 Inclusion of measures to ensure land drainage outside the embankments will continue
adequately following the realignment.
 The possible effect on the coastline bordering the realignment. Ensuring they are
minimal or can be mitigated.
 The need to mitigate for the effect on fresh-water and terrestrial ecology already
present on the realignment site.
 Possibilities for supporting new recreation opportunities as part of the scheme without
extra costs.
 Aspirations for additional recreation and other enhancements which could not be
included in the scheme.
Technical Details
Numerical modelling and coastal process investigations were undertaken to assess the wider
scale impacts on the adjacent coast and to explore how options function in relation to their
stability, development, inundation and habitat creation. The modelling also considered the
impacts of the Bunn Leisure proposals on the proposed options. The results of these
investigations were a key driver in the selection and development of the preferred option.
The history of managed realignment schemes has been summarised by Dixon et. al. (2008)
and Rupp-Armstong et. al. (2008). Medmerry differs from previous managed realignment
schemes as it is the first to promote managed realignment as a flood risk management
measure on the open coast. Previous schemes have largely been promoted for sites adjacent
to estuaries. Medmerry has similarities with the site at Porlock in Somerset where a natural
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realignment was formed by a storm in 1996, but the site at Medmerry is more exposed to
prevailing south-westerly winds and waves. This project’s numerical modelling and coastal
processes studies have applied available tools and knowledge in an innovative way involving
an integrated set of discrete models and investigations. These have included breach and tidal
inlet stability assessments, coastal process investigations and reviews of existing case studies,
hydrodynamic and sediment modelling and habitat mapping. The conclusions of these studies
were combined through expert interpretation by the team’s consultants and scrutinised and
approved by external expert peer reviews.
The importance of sharing major assumptions and outputs from the core project team with all
the groups involved in designing the scheme was recognised from the start. For the technical
design team, this involved consideration of timing and formats of reports to make information
available for comments that could affect the scheme design. Tools for visualising the
finished scheme were important to help those involved understand the details.
Environmental Details
An EIA was required for the project as the planning authority considered that there would be
a significant impact on the local environment. As discussed, the land taken up by the
realignment is mainly used for low-grade agriculture. The EIA highlighted main
environmental impacts including the presence of a number of protected species (water voles,
reptiles and great crested newts), the potential for disturbing unknown archaeology, impact
on public rights of way and the change to the landscape that will take place. The design of
the scheme must incorporate measures to mitigate for the impacts to these receptors from
building the new embankments and creating new intertidal habitat. Water voles are a
particular issue as existing drainage channels provide habitat for a local population
stronghold. The strategy for mitigating these impacts is therefore central to the design of the
scheme.
In creating the new inter-tidal habitat, a key driver is to maximise the area of new habitat
created and the new wildlife opportunities it will offer. Natural development of a stable site
was favoured with minimised need for further intervention. However, details of the scheme
design were carefully considered in order to create the best possible habitat from the outset.
The large material volumes required to build the new embankments will be dug from areas
designed specifically to promote the formation of tidal channels and habitat. In consultation
with the RSPB, opportunities have also been identified for the creation of high level bird
roosting sites for overwintering and breeding birds.
Community involvement
Public acceptance has long been recognised as important in promoting managed realignment
schemes. Engagement planning was a high priority in designing and gaining approval for the
scheme. The team had the advantage of being able to build on previous engagement for the
strategy and SMP in the local area and gain from the experience of implementing schemes
elsewhere. As a result of earlier engagement, local communities generally accepted the
managed realignment option but significant concerns still remained.
 The ability of the proposed inland embankments to withstand storms.
 The loss of agricultural land and recreation opportunities.
 The perception of wildlife interests being prioritised over properties and land.
 Changes to inland drainage.
 Ease of access to the coast and ability to walk between local villages.
 The effect of changes on holiday parks important to the local economy.
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The approach to stakeholder engagement was described by Miller et. al. (2010). It followed
the ‘building trust with communities’ model used within the Environment Agency and
applied a stakeholder engagement plan that focused on three core objectives:
 To provide information about the multiple benefits offered.
 To gain widespread support for the implementation of the scheme.
 To get community input into the design.
The plan specifically included engagement methods to ensure that the concerns already
voiced could be addressed and where possible, resolved. The issues were explored together
with MStAG and were considered in defining the scope of work in planning the scheme.
This enabled people’s main concerns to be fully integrated and local knowledge to be used in
the design.
The potential opportunities of the scheme were considered with MStAG, exploring what
people would like to see included to enhance the local area. Ideas mainly focused on
improving recreational and local tourism opportunities through inclusion of measures such as
footpaths, bridleways and cycle routes linking into the existing network. The views of local
residents who would rather not see their privacy compromised by access enhancements were
also explored among the group.
Regular meetings and workshops were held with MStAG throughout the design of the
scheme where updates were given by the project team, options explored and questions
answered. When differing opinions were raised, the group sought to find a compromise that
the project team could use in its scheme design. In this way, meetings helped to save project
team resource, which might have otherwise been needed to meet with each community group
individually. This approach also allowed for more transparent decision-making.
The planned engagement also enabled requirements to be defined and expectations to be
managed. As the engineering and habitat creation aspects of the scheme were defined, these
were fed into discussions with MStAG together with advice on what was needed to make the
scheme acceptable to the planning authority. Many of the enhanced access requirements
could be included with little extra cost by making use of maintenance tracks on the site.
Other requirements were beyond the scope of the scheme and could not be included.
The project team helped members of MStAG form an ‘aspirations group’ to explore funding
and details of requirements beyond the scope of the scheme. Fully involving local people in
the design process and focusing on the opportunities offered was beneficial both in improving
the scheme’s ability to meet the defined objectives and in gaining local support and
enthusiasm.
Outcomes
A separate plan was prepared to address each of the three project objectives in planning and
gaining approvals for the realignment (Figures 1, 2 and 3).
The engineering construction shown on Figure 1 for the scheme is relatively straightforward.
A total length of 6.7km of new embankments will be constructed stretching up to three
kilometres inland. The height of the banks will vary from less than one metre to more than
four, making use of the natural rise of the land. Land drainage will be channelled into the
realigned area through new outfalls and a new relief channel will be constructed between
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catchments to the west of the scheme area. After the inland banks are built, a single opening
will be cut through the existing coastal shingle bank allowing tidal flows into the site.
Construction will begin in autumn 2011 and will be completed in 2013.
One key finding of the technical appraisal was that the future stability of the scheme depends
partly on having a large enough tidal exchange to ensure the coastal breach does not close.
The larger the volume of water entering and leaving the site with the tide, the less likely it
would be unstable. Sharing this information among each of the three groups enabled all to
realise that the need for maximising the intertidal area supports both habitat creation and
flood risk management objectives.
Reducing Flood Risk
The realigned embankments will reduce the risk of flooding currently faced and the
maintenance required. The banks will be built taking into account sea level rise over the next
100 years. Standard of protection will initially be better than 0.1% (1 in 1000) chance of
flooding in any year, falling to 1% (1 in 100) in 100 years time. The Environment Agency
will continue to work with Bunn Leisure to ensure works are completed to reduce the risk of
coastal flooding across the whole frontage.
Figure 1 Scheme design outline
Habitat Creation
Up to 300 hectares of new intertidal and transitional habitats will be formed by the
realignment to compensate for anticipated coastal squeeze losses across the Solent over the
next 100 years. An estimated 163 hectares of new intertidal habitat will be created shortly
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after construction is completed as illustrated on Figure 2. Medmerry will be an important site
for bird life and conservation management among the northern shores of the Solent and will
help provide habitat connectivity between Pagham Harbour to the east and Chichester
Harbour to the west. In the future, the site will be managed to balance the needs of wildlife
and enhanced recreation opportunities. The scheme includes the formation of new habitat
areas specifically for protected species including water voles which will be displaced by the
realignment. These habitat areas will also be maintained and improved through future
conservation management of the site.
Figure 2 Creation of new intertidal habitats
Community Involvement and Recreation Enhancements
Representatives of local communities have helped design the scheme by defining
requirements for incorporation in the scheme from the outset. The MStAG group helped the
project team resolve the priority of different requirements where there were conflicts or
aspirations could not all be achieved. The Planning Authority’s minimum requirements were
brought together with the environmental needs and engineering design of the scheme.
The scheme design has incorporated enhanced access at Medmerry. New footpaths, cycle
routes, bridleways, car parks and viewing points will be built as shown on Figure 3. A new
access route for emergency vehicles to reach Selsey is included for use when the vulnerable
B2145 road is blocked. An aspirations group has formed to pursue the inclusion of extra
access enhancements linking the realignment area with the wider path and cycleway network.
Planning permission was gained with support from communities in November 2010 and the
business case was approved by the Environment Agency in January 2011. Environmental
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mitigation actions will commence during spring 2011 and construction will start as
programmed in autumn 2011.
Figure 3 Access and enhancement proposals
Conclusions
When considered on its own, the engineering design for the managed realignment scheme
was relatively straightforward. Working to achieve multiple objectives made the design
process more complex. Encouraging the involvement of stakeholders with potentially
conflicting interests from the start required time, effort and resources but the dialogue
promoted helped those involved to understand each others’ positions and reach agreed
solutions.
The scheme has been designed to meet the requirements to reduce coastal flood risk, enhance
nature conservation by creating new intertidal habitat and incorporate the local priorities for
improved recreation and access opportunities. Those involved in designing the scheme have
helped explain and promote the scheme to the wider local communities and gain support as
its planning application was considered.
The vulnerability of the peninsula around Medmerry to coastal flood and erosion risks has
been recognised increasingly over the last ten years. Local groups have been considering
strategies for adapting to changes that will occur. Work on the managed realignment scheme
has provided a focus for local people to be involved in helping shape the future landscape of
the area and the opportunities that are presented as it changes.
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References
Economic Valuation of Environmental Effects Guidance. (Environment Agency, 2010)
Managed Realignment Electronic platform - www.intertidalmanagement.co.uk
Medmerry Managed Realignment Project Appraisal Report (Environment Agency, 2010)
Miller, S., Giacomelli, J., Hyam, P., Pearce, J., Lewis, P., Pizer, L., and Wilson, G.,
‘Designing the ‘right’ scheme through community involvement: lessons learned from
community engagement on a coastal protection scheme.’ Defra and Environment Agency
Flood and Coastal Risk Management Conference (2010)
North Solent Shoreline Management Plan (2010)
Pagham to East Head Coastal Defence Strategy (Environment Agency, 2009)
Rupp-Armstrong, S., Scott, C. and Nicholls, R., 2008. ‘Managed realignment and regulated
tidal exchange in northern Europe – lessons learned and more.’ Defra 43rd Flood and Coastal
Management Conference, Manchester July 2008. 9p.
Solent Coastal Habitat Management Plan (2003)
Somerset Coastal Change website - www.somersetcoastalchange.org.uk