Rising Seas, Changing Coastlines
By David E P Dennis
This odd idea came to me a few years ago – but why would the people of Hastings and Bexhill want to move to Eastbourne?
A clue to this puzzle is coastal erosion. In the past 7,000 years we have lost at least one third of a mile of land from our coast. Our shoreline is protected in places by sandstone sea cliffs. You can see these at Rock-a-Nore and at Galley Hill near Ravenside Retail Park.
In many places now, winter pounding by waves has cut a small nick in the base of sea cliffs, undermining strata and causing rockfalls. Debris crashes to the beach, often in spectacular landslips, then crumbles into smaller stones. The remaining bedrock structure, called a wave-cut platform, is a flat stone area for the sea to run over – to make yet another cut, enabling the sea to conquer more land.
These eroded pebbles form our beaches. Material is transported along the coast by an eternal system called longshore drift. Instead of the waves striking the coastline at ninety degrees, they strike at an oblique angle, lifting stones along the coastline from west to east. To slow the movement of the stones, humans build wooden groynes. To stop flooding we have built sea defences, and to provide safety to ships – harbour arms and breakwaters.
Civilisation is now everywhere: homes, roads, railways, promenades, power lines, gas and water pipes. The beaches and sands are assets too, for recreation and freedom; to stand in the breeze and smell the salt air.
By now you may see why I felt a few years back that we should all move to Eastbourne. It is because if we still want beaches at Hastings and Bexhill, then we will need to exert influence – to persuade the people of Eastbourne not to defend their coast. If they give fundamental protection to their section of the coastline, there will be no more rocks falling from Beachy Head and therefore no more pebbles coming our way down the coast on the longshore drift. Yet tides will still scour our own beaches here in Hastings and Bexhill. Eventually we will lose all our beach stones, no more will arrive and thus the sea will strike our coast more severely, eroding it at a rate of 20cms a year. To prevent this from happening, we will need to persuade government to buy more barge-loads of enormous granite boulders from Sweden to make defences. Some of these massive rocks are here now (see pics).
How likely is this doomsday scenario? Scientists have been measuring the amount of radioactive beryllium in our coastal rocks and so they know the rate of erosion has risen from 2cms a year in ancient times to ten times as much now.
Back in 2016, Dr Dylan Rood from Imperial College London told BBC News: “The coast is clearly eroding, and Britain has retreated fast. A nearly tenfold increase in retreat rates over a very short timescale, in geological terms, is remarkable.
“The UK cannot leave the issue of cliff erosion unresolved in the face of a warming world and rising sea levels. Cliff erosion is irreversible; once the cliffs retreat, they are gone for good.”
The Greenland Factor
Wave-cut platforms and longshore drift are not the only problems. As the Earth warms, so the distance between the molecules of seawater increases – the sea is bulking up. We know that when we heat water in a kettle, it expands. The ocean is a kind of kettle, the warmer it is, the more sea we have. When the wind blows and the tides are high, we get storm surges. These can easily overwhelm the land, causing death and destruction. Each part of the coast has its own vulnerabilities. At Pevensey and Normans Bay one thousand years of work have gone into draining the marshes. If Eastbourne alone protects its coastline, then this vast marsh could have its protecting beaches scoured, so Pevensey needs protection too.
So what are the forecasts for the near future? Measurements of c – a trace element used to determine geological age – taken at the Hope Gap wave-cut platform near Eastbourne reveal a rate of erosion of 20-30cms over the last 150 years.. Ninety percent of the energy trapped in our atmosphere by greenhouse gases is absorbed by the seas. Greenland’s ice sheet dumps over 280 billion metric tons of melting ice into the ocean each year, making it the greatest single contributor to global sea level rise. A 42-square mile chunk of the Arctic’s largest remaining ice shelf broke off in northeast Greenland, prompting scientists to warn that record-breaking temperatures are accelerating ice loss. Consequently, the Met Office has dramatically changed its coastal flooding forecast. The severity of the future rise is strongly dependent on the assumed future greenhouse gas emissions, or emissions scenario, used. Under a low emissions scenario, sea levels will rise by up to 2.2 metres for London and the south-east. Under a high emissions scenario, this increases up to 4.3m for our area. The research found that at some locations the 1 in 10,000-year flood event of today could be expected more than once per year by 2300.
What Will Happen to Us?
A high emission scenario for London would affect Eastbourne, Bexhill, and Hastings most severely. The sea would be 4.3m (14 feet) higher than it is now, overwhelming all sea fronts and town centres, especially in winter storms with onshore winds and high tides. People may say – well, 2300 is a long way off, but remember the rise is progressive. Things are already becoming more difficult for our coastal resorts. Flood risk is rising.
So, has Eastbourne decided? Well, Chancellor Sunak has just given Eastbourne and Pevensey 16.5 million pounds for flood defences, when it was revealed that Eastbourne would be completely underwater by 2100 without the money. So it seems likely that the pebbles so kindly donated by Eastbourne will gradually cease, leaving us in Hastings and Bexhill to shore up our shores with rocks. Sadly for us in Hastings and Bexhill, it is too late to move to Eastbourne to change their minds.
Or maybe we should move after all – as they now have the money to protect themselves!
• To see more about what will happen to Eastbourne without flood defences, go here: www.eastbourneherald.co.uk/news/what-eastbourne-could-look-2100-935904
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