What is changing our coastline?

What causes coastal erosion?

The causes of coastal erosion and the reasons why one area erodes more quickly than another are due to the complicated interaction of many different factors including the following:

• force exerted by waves and storms erodes the coastline

• current and tidal movements can result in sediment being deposited along the coast

• geology of the coastline will affect the speed at which erosion takes place

• presence of artificial sea defences in one location can affect rates of erosion in another location

• climate change events such as sea level rise and increased storminess can speed up the erosion process

What are coastal defences?
Coastal defences aim to reduce erosion and flooding of the coast and as such protect land, houses and businesses from falling into the sea. Nature provides its own defences against the sea such as sand dune systems, cliffs and saltmarshes. They absorb and dissipate the force of the sea and reduce the risk to people and property. Artificial sea defences such as a sea wall, an earth embankment or groynes placed across the beach also protect our coast from erosion and flooding. However these types of artificial defences are unable to adapt to changes in the environment and by interfering with natural processes, might cause problems further along the coast.

What Problems do we face in the future?

The possible impacts of global warming are still being debated by scientists. However, it is widely accepted that sea levels are rising and will continue to do so in the future due to the thermal expansion of sea water and the melting of Polar ice caps. This is compounded by the fact that the UK is naturally ‘tipping’ into the sea, with south eastern England sinking as western Scotland rises out of the sea. Scientists predict that by the 2080s the average sea level in the English Channel will stand 54 cm higher than present. There are a large number of uncertainties such as volume of greenhouse gases emissions, rate of ice melt and accuracy of climatologists computer models which give us a range of scenarios for the future. However even the low emission scenario predicts a rise of 19cm by 2080 for SE England and taking into account other changes such as more violent and more frequent storms, the effects on the coastline could be disastrous. Doing nothing is an option but is it responsible to sit back and wait for problems to occur and then react? Whether we like it or not, climate change is now accepted to be an over-arching issue which will have an impact on the whole of the south east of England. Some of the predictions and their likely impacts may be uncertain, but a sensible analysis of the risks suggests that a responsible way forward is to plan now how we can adapt to the changes that may occur in the future. In the long term it is unlikely in many areas that we will be able to maintain the coast in the same position as it is today, as this would cost the nation millions of pounds each year and we would need ever-increasing sea walls to cope with sea level rise and bigger waves. The cost is both financial (through materials, labour and planning) and environmental (through construction damage, changing coastal processes and sourcing of materials). However, these costs have to be weighed up against the cost of losing farmland, houses, roads and businesses. We therefore need to think realistically about what our coastline is going to look like in the future, whether there are more sustainable solutions and how we can plan for these changes.

Narrowing of the intertidal and the subsequent loss of habitats has been reported in research recently published in the journal of the Royal Geographical Society, this stated that:

“more than 1,000 sections of beach on the south coast have experienced the greatest steepening. In the Solent the distance between high and low tides has reduced by between 50% and 90% in places.”

The Foresight Project, which was commissioned by the Government to consider the future impacts of flooding, recently reported that:

“continuing with existing policies is not an option … hard choices need to be taken – we must either invest more in sustainable approaches to flood and coastal management or learn to live with increased flooding.”

What is Coastal Squeeze?

A further cause for concern is the phenomenon called ‘coastal squeeze’. As sea levels rise, coastal habitats such as saltmarsh, if in an entirely natural situation, would respond by moving landward or “rolling back” to adjust their position. Fixed man-made structures such as seawalls prevent or severely limit this landward movement. The coastal habitats are therefore ‘squeezed out’ between rising sea levels and fixed defence lines as shown in the diagram. Therefore where any sea defences are maintained there is likely to be a loss of habitat in front of the defences. This is a real challenge in areas such as the Solent where internationally important habitats fringe a heavily defended and populated coastline. The need to protect internationally important conservation sites is only part of the reason for looking after these habitats as they:

• provide a natural sea defence, absorbing the energy of waves

• provide a clean, healthy and attractive environment for people to enjoy which adds to our overall quality of life

• provide a haven for sailors

• provide inspiration for artists

• contribute to the local economy through visitor spending

• provide a vital source of food and shelter for commercially exploited fish

• stabilise the mud around the edges of estuaries

• help maintain water quality

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