COULD GLOBAL WARMING BRING TSUNAMIS TO WALES?
EVERYONE remembers the horrific pictures of the 2004 tsunami that devastated Sri Lanka and Indonesia. Causing $20bn of damage and leaving more than 200,000 people dead or missing, it was one of the worst humanitarian disasters in recent memory.
The vast majority of tsunamis are caused by earthquakes. As Wales is not near any major fault lines, people assume there is no risk of a huge wave hitting the Welsh coast.
However, new research suggests the chance of a devastating wave hitting the Welsh coast has increased due to climate change.
We spoke to experts to find out what would happen if a large wave hit Wales and whether it is something we should worry about.
There have actually been several tsunamis that have crashed into Wales over the centuries.
One of these followed the Lisbon earthquake in 1755. This caused anywhere between 10,000 and 100,000 deaths in Portugal and almost totally destroyed the city of Lisbon. This wave created was three metres on the Cornish coast and it’s very likely it also hit the Bristol Channel.
Some experts think the 1607 Bristol Channel floods were also caused by a tsunami.
During this flood Cardiff was one of the worst-affected areas, with devastation stretching from Laugharne in Carmarthenshire to above Chepstow on the English border.
Plaques on the sides of surviving churches, such as those at Wentloog, near Cardiff, and Goldcliff, near Newport, show the water going up to 8ft high.
St Mary’s Church in the centre of Cardiff was very badly damaged. Some walls fell and corpses were washed out of the graveyard.
A flock of 500 sheep was drowned at Llandaff, near the site of the present cathedral, at least half a mile inland.
During this survivors clung to the steeples of churches and to the roofs of the few buildings which remained standing.
One of the leading academics on this theory is professor of physical geography at the University of Wales Trinity St David Professor Simon Haslett.
According to Prof coasts are at some risk.
He said: “All coasts are at risk of tsunami and the 1755 tsunami, generated from an earthquake offshore near Lisbon, hit Cornwall, Devon and southern Ireland, with waves up to 3m (9ft) high, and is very likely to have hit the western South Wales coasts of the outer Bristol Channel, Haslett, all although there are no records I can recall.
“The 2004 Boxing Day tsunami in the Indian Ocean travelled around the world and seems to have been recorded on the Milford Haven tide gauge, albeit only a few centimetres high by the time it reached South Wales, but it indicates the global reach of some of these events.
“In my review paper I also identified small tsunami waves created in Milford Haven by an earthquake in 1892 but they caused no damage.
“However, Dr Ted Bryant and myself proposed a theory that the 1607 flood in the Bristol Channel was caused by a tsunami and caused around 2,000 deaths.”
When it comes to what the impact of a wave would be it depends on three things – the wave size, the tide, and the coast.
According to Prof Haslett, living near cliffs is safer.
“The extent of the inland penetration of a tsunami is dependent not only on the size of the wave but on the topography of the coast,” he said.
“For example, on cliffed coastlines even large tsunami cannot get much further than the cliffs themselves, although tsunami can sometimes mount the clifftops and deposits boulders there.”
Some parts of Wales are more at risk than others, with communities several kilometres inland at risk.
Prof Haslett said: “For coastal lowlands, like the Gwent Levels for example, once a tsunami gets over the sea defences it may travel inland for several kilometres until it runs out of steam.
“This was seen tragically in both the 2004 Indian Ocean tsunami and the 2011 Sendai tsunami in Japan, where there were locations where the tsunami mounted and inundated low-lying agricultural land as a high bore that was very destructive and penetrated up to 5km inland in the case of Japan.
“In South Wales and Somerset there is the added factor that the coastal lowlands like the Gwent Levels and Somerset Levels slope inland, so even when a tsunami that is travelling across the lowland runs out of steam the water would continue to run downhill until the ground rises.
“For the 1607 event, Ted and I suggested that was how the flood waters seemed to have reached the foot of Glastonbury Tor some 22km (14 miles) inland from the sea.”
The geography of South Wales could also make a potential tsunami more damaging still. This is because the Bristol Channel could increase the size of the wave.
“Our modelling linked to the 1607 event suggests that a moderate-sized tsunami entering the Bristol Channel could be amplified by the funnelshape of the channel and Severn Estuary,” said Prof Haslett.
“Our data suggested that a possi-