Managed Retreat as a Viable Option for Coastal Management
There has long been a threatening presence to the low lying flat land of the southern coastline of England and the Welsh coast from the sea. This is due to the increasing intensity of weather events and the ever rising sea levels. (1)
Sea level rise
Since 1993 sea level rise is estimated to be increasing between 2.6 and 2.9 millimetres per year. (2) This increase is expected to continue for centuries due to the long response time for parts of the climate system and slow inertia. It has been estimated that for each degree Celsius of temperature rise there is, we will see a sea level rise of approximately 2.4 metres. (3)
The cause of this observed sea level rise is due to two mechanisms:
- Thermal expansion: when the ocean water expands as it warms due to the increase in ocean heat content. (4)
- The melting of vast stores of land ice such as ice sheets and glaciers.
Both these factors have the potential to considerably affect human populations and marine ecosystems in coastal and island regions. (5) As a result, many of the 30 million people living near the UK's coastline will need to anticipate how climate change will affect them in the future. (6)
Coastal Management Options
In order to protect these coastal regions, councils will be forced into making a difficult decision to choose some form of coastal management; there are four key techniques that can be considered:
- Hold the line – maintain existing coastal defences
- Advance the line – build new defences further out at sea to dissipate the energy of the sea and reduce the stress on existing defences.
- Retreat the line (Managed Retreat) – relocate residents in danger zones and let the sea reclaim the land.
- Do nothing – let the land flood and deal with it as it comes (approach usually used in unpopulated areas) (7)
The U.K.’s Environment Agency along with many Councils are experimenting with this kind of coordinated retreat for the hardest to defend coastal areas. It’s a controversial approach for a relatively small nation. However, the recent wild winter storms are starting to change attitudes, therefore strategic surrender suddenly seems like it may be the smart, sustainable solution. (8) This is mainly being utilised along the south coast of England and the Welsh coast with around fifty communities already earmarked for some form of retreat. (9)
One example of this is the picturesque coastal resort of Fairbourne in Cardigan Bay, Wales. The local council have stated that they intend to abandon the sea defences due to the increased cost of maintenance and ultimately surrender the village to the mercy of the sea. This has caused house prices to plummet, meaning residents are struggling to sell up and move on from the area. In turn, this has invoked legal battles with land owners looking for compensation from the local authority. However, the council argues that the risk of overtopping of the current defences, or worse still breaching would have immense consequences and put people’s lives at risk. (10)
Another area where this approach is being put to the test is a scheme at Medmerry in West Sussex where 7km of shingle banks are being constructed 2km inland. The Environment Agency state that this will reduce the risk of flooding to hundreds of homes and will produce a wet land/salt marsh habitat which will attract many different species encouraging increased tourism due to the broader ecosystem. (11) This form of coastal realignment not only moves the sea wall further inland, it also creates a powerful buffer zone of marsh that can absorb storm energy. (8)
Managed retreat has the potential to be a very cost effective solution to the inevitable future sea level rise. It has the ability to naturally replenish nearby beaches due to the encouraged coastal erosion, providing protection and balance to the surrounding coastline. It can also produce large areas of saltmarsh which can offer habitats for a vast array of different species and will in turn attract tourism to these areas. However, a certain amount of land will be destroyed in the process of managed retreat resulting in loss of settlements, farmland and natural habitats. This loss of land can lead to fierce legal battles between residents in the proposed area and councils who have decided to retreat the current coastal defences. Therefore, it’s often not seen to be a socially acceptable option to explore and due to the poor monitoring of current and past managed retreat schemes it’s led to there being little evidence to base future projects on, causing them to be extremely unpredictable. (12)
1. Sea surrender plan to ease flood fears on south coast, 2013. Available at: http://www.bbc.co.uk/news/science-environment-24770379
2. Christopher S. Watson, Neil J. White, John A. Church, Matt A. King, Reed J. Burgette & Benoit Legresy Unabated global mean sea-level rise over the satellite altimeter era, 2015.
3. IPCC FAQ 5.1: Is Sea Level Rising?, in IPCC AR4WG1, 2007.
4. Albritton et al., Technical Summary, Box 2: What causes sea level to change?, in IPCC TAR WG1, 2001.
5. Fischlin; et al., "Section 4.4.9: Oceans and shallow seas – Impacts", in IPCC AR4 WG2 2007, Chapter 4: Ecosystems, their Properties, Goods and Services, p. 234
6. Climate change 'will wreak havoc on Britain's coastline by 2050', 2011. Available at: http://www.theguardian.com/environment/2011/mar/06/climate-change-coastline-joseph-rowntree
7. Coastal Management, Available at: https://geographyas.info/coasts/coastal-management/
8. One English Town’s Innovative Response To Sea Level Rise, 2014. Available at: http://thinkprogress.org/climate/2014/04/09/3422063/england-town-sea-level-rise/
9. Sea level threat to force retreat of communities in Wales, 2014. Available at: http://www.bbc.co.uk/news/uk-wales-26125479
10. Village of the DAMMED, 2016. Available at: http://www.dailymail.co.uk/news/article-3442264/Welsh-village-decommissioned-warnings-lost-sea.html
11. Sea surrender plan to ease flood fears on south coast, 2013. Available at: http://www.bbc.co.uk/news/science-environment-24770379
12. Wolters, M., Bakker, J.P., Bertness, M.D., Jefferies, R.L. & Moller, I. . Saltmarsh erosion and restoration in south-east England: squeezing the evidence requires realignment. Journal of Applied Ecology, 2005.