A new report by the Institution of Civil Engineers and the Royal institute of British Architects predicts that major cities including Portsmouth could be largely under water by the end of the century and so have to rethink the way they are organised.

The report explores managed retreat from the coast. For example: Hull's historic city centre would be limited to an island reached by bridges and Venetian-style water taxis, while in Portsmouth large parts of Portsea island would be given back to the sea while new "hillside living" developments would be built on densely packed hillside terraces, akin to the towns of Italy's Amalfi coast.

There's going to be an exhibition linked to this report at Portsmouth Cathedral from 15-27 Feb which will include illustations and designs for the proposed new cities.

15th – 27th  February -  Exhibition -  Flood: Facing Up to Rising Sea Levels Joint project between RIBA Building Futures and the Institution of Civil Engineers scrutinising the current practice of coastal flood management in the urban context.

To read the Guardian article

To read the report Facing up to Rising Sea Levels. Retreat? Defence? Attack?,

Response from Bret Davies Coastal Engineer Havant, Portsmouth & Gosport Coastal Partnership

Introduction

Portsmouth is the home of the Royal Navy and the City is proud of its distinguished maritime heritage but it is also a City of ideas and development and given its proximity to the sea the Council recognises the need to adapt to climate change and rising sea levels.

In order to do this sustainable management of the long-term flood and coastal erosion risks is required in order to balance the needs of the population with the needs of an internationally important environment.

The Coastal Partnership was set up between neighbouring coastal authorities - Portsmouth City Council and the Borough’s of Havant and Gosport to deliver a more strategic approach to managing the risks associated with the shared coast allowing economies of scale but also strengthening the team on strategies, coastal monitoring and asset management.

With the limited space available Portsmouth faces a considerable planning challenge from the South East plan to accommodate an additional 14,700 residential units by 2026. The emerging Portsmouth Plan (the Core Strategy) is seeking the space, through sequential testing within the existing city boundary to accommodate this. The City Council does not work in isolation and experiences issues that are shared across South Hampshire and the Partnership for Urban South Hampshire was set up to deliver strategic solutions to shared.

The case study referred to today clearly shows the combined issues we face as an authority.

Initial Opinion

We were surprised that this report only covers the present day 2010 to 2100 years and not 2100 years to 2200 because we are developing detailed studies which give us the current long-term sustainable option for the city through the Portsea Island Coastal Strategy Study, the Portchester to Emsworth Coastal Flood and Erosion Risk Management Strategy and the emerging North Solent Shoreline Management Plan which is going to public consultation next month.

Unfortunately we have not been engaged through development of your report which is rather ironic because your report states on page 4: “a recurring theme is of inadequate consultation, co-operation and unity between public agencies” but I won’t dwell on that. The reports’ shock and awe approach is exactly what the coastal and flood risk community require in order to engage the public and to move forward with issues such as Coastal Change and Community led schemes.

Challenges NOT constraints:

As a Council we are regularly faced with the challenges that you refer to in your paper – limited resources, We have been actively trying to address the issue of ‘above design conditions’ (Page 4) when we submitted the coastal strategy for Portsea Island we directly asked the Environment Agency to consider this. However, due to the constraints of the current business justification process, limited resources and the current economic situation we must seek other creative opportunities for investment and incorporate adaptability in any design solution. Where sites for regeneration are emerging around Portsmouth’s coastline as a Council we will look at funding opportunities not only from flood risk pots or developers but from external contributions such as art, recreation or tourism grants to increase opportunities. The Cleveley sea defences is a great scheme and is often referred to as best practice, we see it as a benchmark that we are looking to exceed!

The emerging North Solent Shoreline Management Plan will give central Government a feel for what investment is necessary for the short, medium and long-term and is trying to set realistic policies where “doing nothing” is a distinct and realistic possibility. Within the Portsmouth area consideration of multiple criteria: people, environment, heritage, infrastructure etc is a showstopper. The importance of retaining the City to the local, regional and national economy far outweighs the losses.

Communication – it is always good to visualise who needs to be involved in a project and at what level, your flow diagram/image is a good representation of this confusion and we are developing the Surface Water Management Plans “Washing Wheel” for our own specific needs. We see communication as the mechanism to overcoming the challenges we face to avoid any missed opportunities but also to educate the public or to educate our peers.

Through the planning process we ensure developers are fully engaged and aware of their responsibilities. The Partnership for Urban South Hampshire hosts a website where developers and the public can freely access information on flood risk issues across the PUSH region that would otherwise be difficult to compile and we engage the public on how best to make their private property flood resistant or resilient.

Timescale – the coastal community always looks over a 100 year horizon and due to the flood risk from the sea to Portsmouth our planning decisions look at the year 2115. We acknowledge that 10 years down the road the science will have changed and we will be working to another data-set – therefore adaptability is essential in everything we do.

As science develops so does our knowledge – only last summer it was discovered that Portsea Island is subject to deviations in height. A student from the University of Portsmouth discovered that during a high tide the island of Portsea would move up by several mm due to an apparent ‘floating effect’

OPTION 1 - Portsmouth Retreats the What if? Scenario!!!

Portsmouth is made up of large areas of reclaimed land and large areas of open space are old landfill sites, therefore the impacts of retreating would release contaminants in to the international designated harbour, combine this with the potential loss of the peninsula’s, which act as control points, at the harbour entrances leading to increasing wave energies in the harbour which could lead to an increased rate of erosion and a rapid loss of mudflat and saltmarsh!

Q – Was consideration given to the implications of allowing the sea to reclaim contaminated land?

Relocating the M27 would be a PUSH wide initiative and the decision for this change would need to be mutually agreed across the region.

Managed Realignment (or Retreat) has been considered by both the emerging North Solent SMP and the Portsea Island Coastal Strategy Study. Due to the existing community at risk and lack of suitable space to realign in Portsmouth it is not feasible to do this but the North Solent SMP has recognised that it may, subject to studies, be considered to the unpopulated but heavily designated site of Farlington Marshes.

HOW DO WE RETREAT FROM A POPULATED AREA? Communities? Eg. Northney, Emsworth & Langstone

OPTION 2 – Portsmouth Defends

·        “We no longer need to defend the inner perimeter of the harbours” – Q - what would happen in the event of the tide gates failing?

·        Gates would defend areas that may not need protecting, perhaps this solution is more of an “attack” solution?

·        How would the threat of underwater attack be managed or even afforded to a fleet of Navy vessels in open water? Have the Royal Navy been approached?

·        This option demonstrates a significant use of public open space. How would the public feel about the loss of open space and their beach? The impacts on loss of tourism to the city could be far reaching.

·        Actively encouraging development in the flood plain!

·        CAN THE DEFENCES THEMSELVES BE DESIGNED IN SUCH A WAY THAT CAN MAKE THEM ECONOMICALLY AND COMMERCIALLY VIABLE? It is a great question, the answer is probably yes, why not?

OPTION 3 – Portsmouth Attacks

We need to be open minded about this approach, we have already seen many solutions to this issue globally and could be a self-sufficient lifestyle if combined with green energy solutions (wind/tidal power)

SUMMARY

This is an academic hypothetical what if? piece of work and will not influence the current decision making process but does provide food for thought. The City of Portsmouth provides an interesting case study because it has all the characteristics of the UK within a relatively small geographical area - an urban population surrounded by sea, a diverse coastal habitat and limited space for development but the City is already preparing for the long-term future. The City Council are developing long-term coastal flood and erosion risk management strategies for the Cities coastline that look at the impact of sea level rise over the next 100 years and the emerging Portsmouth Plan will determine what type of development we want to see, where it can be suitably located and address how we are going to make it happen.

All the work we have done to date indicates that investment in the city as it is, is currently sustainable and we will continue to, in your terms, “defend” the city. Unless the rules change ofcourse …  

Questions for the RIBA/ICE team:

1. we would be interested to see where this goes from here, will it be going to Government?
2. Have any of these options been costed?
3. What about the target for the South East Plan? Do we still continue with the requirement of 14,700 dwellings or is the challenge now to relocate 40,000 properties and provide an additional 14,700 on top of that?

• Environment
• Sea level

British coastal cities threatened by rising sea 'must transform themselves'

Hull and Portsmouth could be dramatically remodelled, suggests report

 

• Buzz up!
• Digg it (64)

• Robert Booth
• guardian.co.uk, Friday 15 January 2010
• Article history

Hull: Venice of the North? A dramatic sunset over the nearby Humber bridge. Photograph: John Giles/PA

 

Hull could be transformed into a Venice-like waterworld and Portsmouth into a south coast version of Amalfi,