Sea Level Rise and Coastal Defences
Sea level rise is probably the biggest impact that climate change will have on residents of Havant Borough and the surrounding area. The borough boundaries include the coasts of Hayling Island, Langstone and Emsworth with a combined population in these areas of about 30,000.
The rise in sea levels is caused by the seas getting warmer (thermal expansion) and land based ice such as glaciers and ice sheets melting, depositing water into the seas. It is estimated that if all of Greenland’s ice melted, the seas would rise by approximately 7 metres. Just a fraction of this would have a major impact on our local coast.
It has been estimated that sea levels are likely to rise by about 1 metre by the end of the century, such a rise will cause a much greater ingress inland than 1 metre and such figures do not take into account high tides, waves, low atmospheric pressure and storm surges.
With the climate warming faster than anticipated, 1 metre is looking optimistic and sea levels could rise by more than this by the century’s end. Anyhow without drastic cuts in emissions the seas will not suddenly stop rising after 2100, in fact there would be an acceleration in the rise as positive feedback mechanisms cause accelerated warming of the seas and melting of the ice.
An example of a positive feedback is when atmospheric warming causes ice and snow to melt. The white reflective surface is replaced by the darker earth and vegetation which will then heat up and add to the atmospheric warming, causing more ice to melt (a ‘feedback’ loop of events). Other positive feedbacks are caused by melting sea ice, methane released by warming Arctic ground and warming increasing the amounts of water vapour in the atmosphere.
There are a number of outcomes to this:
Migration away from the coast
Although sea level rise will not happen suddenly, unless we get to a carbon neutral level of emissions soon, sea levels could eventually rise to a point where Portsmouth, Hayling Island, Emsworth, and Gosport become unsustainable as liveable areas. Hundreds of thousands of people (if Portsmouth is included) in the area would need rehousing inland and farmland on Hayling Island would be lost forever. It is likely that those that are rehoused would need to be accommodated on farmland, further reducing the amount of land available to produce food.
Potential pollution from previously populated sites
If the migration inland is not managed then there could be significant amounts of pollution as waste remaining in previously populated areas leaches into the sea or is washed away as the sea erodes the land and the buildings collapse. The pollution could include plastics, oils, chemicals, asbestos and other toxic materials.
Short term defence against rising sea levels
The cost of protecting Havant Borough’s coastline against a sea level rise in excess of 2 metres is likely to be prohibitive, for example building a 7 metre high wall around Hayling Island would be very expensive and the concrete itself would be a significant cause of carbon emissions. The only solution to prevent this scenario is to cut carbon emissions. However in the short term some protective coastal defences are possible and this is what government agencies are working on now.
Eastern Solent Coastal Partnership (www.escp.org.uk) is the government agency working with local councils to develop coastal defences that protect against erosion and sea level rise. Apart from cutting emissions you can get involved in the consultations organised by them when they seek public opinion. You can also get involved by writing to councillors and MPs or joining Havant Climate Alliance and other campaigning groups.