Southsea Coastal Schemea


Project outline

8,077 homes and 704 non-residential properties in Southsea are at risk of flooding from the sea. Current defence levels only offer limited protection from coastal flooding and the existing structures have residual lives of less than 10 years, with two major failures in recent years. 
The Southsea Coastal Scheme will stretch 4.5km along Southsea’s frontage and will reduce the risk of significant flooding for over 100 years. It presents a unique opportunity to stimulate regeneration, creating a vibrant place for business and leisure as well as protecting the cultural and heritage features that are important to us all. 
Recommendations from the North Solent Shoreline Management Plan and the Portsea Island Coastal Strategy were used to develop a list of coastal defence options, which were taken to public consultation in November 2014. The preferred option has been progressed to an outline concept design, which has been submitted to Defra as part of an outline business case. The project will now move through the Design Development, Consultation, Principal Design, Consenting and Detailed Design phases before commencing construction. 
The project is being led by Portsmouth City Council and Eastern Solent Coastal Partnership. The outline concept design was undertaken by Royal HaskoningDHV. Balfour Beatty have been appointed as principle contractor through the the Scape Procure framework. A multidisciplinary design team, led by Arup and supported by Ramboll, have been commissioned to undertake the detailed design. The scheme is funded and assured by the Environment Agency, Defra and HM Treasury. 
Design development work commenced in August 2017, and principal design work is scheduled to be completed by July 2018.  Consenting / Licensing and Full Business Case submission is programmed for October 2018. Construction is anticipated to commence in April 2019. 


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Detailed project information


This project has the opportunity to:
  • Reduce coastal flood and erosion risk to people and property
  • Improve and enhance the coastal environment
  • Enable regeneration of the Southsea frontage
  • Promote high quality urban design
  • Improve access to and the enjoyment of the coast

£949.7m worth of assets including 8,077 homes and 704 commercial properties in Southsea are at risk from flooding from the sea over the next 100 years. Modelling has shown that a major flood event would result in 4,114 properties inundated with water with a further 3,963 properties indirectly affected by the flooding through loss of access. 

In the worst affected areas water would be fast flowing with depths over 4 meters deep posing a considerable danger to public safety (See picture below). Five scheduled ancient monuments, multiple nationally and locally listed structures, three conservation areas, one registered park and key infrastructure also lie within the area at risk. 

Flood extent showing depth of water (Present day 1 in 200 year event)

The Southsea Coastal Scheme will replace 2.8 miles (4.5km) of ageing coastal defences from the Royal Garrison Church to Eastney Barracks.

With current defences reaching the end of their existing life (some dating as far back as World War II), it is important that we adapt our coastline to reduce flood risk moving into the future. An overview of the historical development of Southsea can be seen here.

If improvements are not undertaken the current defences will continue to deteriorate with an increasing risk to property and lives. Sea level rise and the increase in extreme weather events predicted over the next 100 years will continue to put Southsea’s coastal defences under increasing pressure.

Recent seawall failures in Southsea

The project aims to mitigate increasing risks of flooding from the sea, and high tides & winter storms.

The coastline has been divided into seven sections to allow future construction to be phased, to minimise disruption during the works. The work is likely to take up to six years to complete once construction gets underway. Click here for our background document on the Southsea Coastal Scheme.

Who is developing this scheme?

The Eastern Solent Coastal Partnership, on behalf of Portsmouth City Council, are leading this project to develop options to reduce flood risk into the future.

The Southsea Coastal Scheme is one of the largest coastal defence schemes in the UK. The new defences will stretch 4.5km along Southsea’s frontage from Long Curtain Moat to Eastney Barracks and will reduce the risk of significant flooding for over 100 years.

Southsea Castle - SketchPyramids Frontage  - Sketch

Potential design concepts for Southsea seafront

The development of the scheme is guided by the North Solent Shoreline Management Plan, a high level policy document setting out a framework for future management of the coastline. For more information on this and its relation to the Portsea Island Coastal Strategy, click here.

The scheme is being delivered by an Integrated Delivery Team (IDT) incorporating Portsmouth City Council, Eastern Solent Coastal Partnership, Balfour Beatty, Arup and Ramboll.

Previous consultations

A big thank you to all who attended our previous consultation back in November 2014. The events were very successful, with several hundred people attending and providing feedback on the plans. To view this exhibition report, please click here.

Coastal defence options

The preferred option for the scheme is a sloped revetment with a setback defence. This was selected from a long list of hard and soft engineering options after assessment against Social, Environmental, Technical and Economic factors. The total cost of delivering the scheme based on the concept design is £87.4m (including contingency).

Map showing the 7 sub-frontages of the Southsea scheme

How is the project funded?

Portsmouth City Council have been allocated £5.9m of grant funding from central government to progress the design phase of the project. This comes following approval of the schemes Outline Business Case by the Environment Agency, Defra and HM Treasury.

On completion of the initial design phase in late 2018 the council will present a Full Business Case to government to apply for the funding for the construction works.