Has Somerset been the victim of a tsunami? Could it happen again? Geographer Dr Simon Haslett discusses the results and implications of his coastal research in Somerset.
Tsunami don’t occur in Britain – do they? Well, yes they do, and one can strike any coast at any time. Tsunami are large waves caused by either submarine earthquakes, landslides, volcanic eruptions or by a comet plunging into the Ocean. They are common in the Pacific Ocean because of the major fault lines and volcanoes that occur there, and as a consequence a Tsunami Warning System has been created across the Pacific. They are less common in the Indian Ocean, and rarer still in the Atlantic.
The Asian tsunami has shown that although tsunami may not be common, when they do strike they can be devastating and, in hindsight, the benefits of a warning system are painfully obvious. The same is true of the North Atlantic where tsunami are rare, but no less severe.
In 1755, a magnitude 9.0 earthquake (the same as the Asian earthquake) occurred in the seabed offshore Portugal that sent a 15 m (49ft) high tsunami that struck Lisbon probably killing close to 50,000 people. The tsunami radiated outwards to damage coastal areas in Spain, Morocco and the Caribbean islands some 5,700 km away – a truly pan-North Atlantic event. It also affected Southwest Britain, being recorded as far north as Swansea.
An earlier catastrophic coastal flooding event occurred in Somerset, and neighbouring north Devon, Gloucestershire and south Wales, in 1607 that appears to have killed around 2000 people and plunged the region into social and economic chaos. Historians have usually attributed the flooding to a storm but new geographical research, that myself and Dr Ted Bryant of the University of Wollongong in Australia have undertaken since 2002, has shown that it was more likely to have been a tsunami.
We published our initial ideas in 2002 in the scientific journal Archaeology in the Severn Estuary. According to contemporary accounts, the flood occurred rapidly in apparently good weather on 20th January 1607 “for about nine of the morning, the same being fayrely and brightly spred, many of the inhabitants of these countreys prepared themselves to their affayres” when they saw “mighty hilles of water tombling over one another in such sort as if the greatest mountains in the world had overwhelmed the lowe villages” – a description closer to a tsunami than a storm.
In summer 2004, Ted and I travelled the length of the Bristol Channel coast from Barnstaple to Gloucestershire to the Gower looking for signs that a tsunami had struck the coast. We were filmed doing this for a BBC2 Timewatch programme originally scheduled for broadcasting in February 2005, but following the Asian disaster its showing has been postponed until the Spring to allow some reediting due to the sensitive nature of the topic.
From our fieldwork we have estimated that a 1607 tsunami would have been at least 5.5m (18ft) high when it struck the Somerset coast, travelling at a speed of 32mph, and penetrating inland as a moving wave for at least 2½ miles from the shore. These results are consistent with the description of “mighty hilles of water” and others that the wave is “affirmed to have runne …. with a swiftness so incredible, as that no gray-hounde could have escaped by running before them”. However, the historical accounts tell us that the waters reached the foot of Glastonbury Tor some 14 miles inland where it flooded alms houses - this is possible as the ground in the Somerset Levels slopes landward, so that when the tsunami wave broke and collapsed the water rushed further inland rather than return to the sea.
The accounts contain a long list of Somerset places that were badly affected, including Berrow, Yatton, Puxton, Congresbury, Kingston Seymour, Worle, Kewstoke, Banwell, Wick, Weston-Super-Mare, Uphill, Kenn, Combwich, Burnham, Lympsham, East Brent, Mark and Brean, the latter four are said to have been “swallowed up” by the wave with 26 fatalities recorded at Brean.
Amongst the Brean victims, a John Good lost his wife, five children, and nine servants as the wave struck, but he saved himself by clinging to thatch that carried him for more than a mile before it washed up on a bank. Thatch seems also to have saved the wife and son of a John Stowe of Berrow, upon which they were washed two miles by the wave to safety; he was not so lucky and drowned with three of his other children. At Bridgwater, “two villages near theirabouts and our market town overflown [by the wave] and report of 500 persons drowned, besides many sheep and other cattle”. The plague hit Bridgwater in 1625, 16 years after the terrible tsunami and within living memory of those that survived it.
At Kingston Seymour a plaque in the church commemorates the event: “an inundation of the Sea-water by overflowing and breaking down the Sea banks; happened in this Parish of Kingstone-Seamore, and many other adjoining; by reason whereof many Persons were drown’d and much Cattle and Goods, were lost: the water in the Church was five feet high and the greatest part lay on the ground about ten days”. The water lay on the ground for such a long time partly because of the landward slope of the ground, and probably because all the sluice-gate keepers had perished.
Apart from the historical accounts and our field evidence, the smoking gun that confirms in my mind that the 1607 flood was caused by a tsunami is the recent report that a previously overlooked contemporary account states that an earth tremor was felt on the morning in question. It is most likely that an active fault system offshore southern Ireland had a significant earthquake that created the tsunami. Indeed, the fault in question has apparently experienced a magnitude 4.5 earthquake in 1980, not big enough to cause a tsunami, but indicates that it may have been able to produce a bigger one in the past. Part of our ongoing research is to establish the frequency of earthquakes and tsunami that have struck the Somerset coast through time.
What has happened before could happen again, and the low-lying areas are now more populated than in 1607, so casualties could be higher. But for a tsunami to have any impact on the Somerset coast the tsunami must arrive close to high tide, because the tide goes out so far in the Bristol Channel, if the tsunami arrived at low tide it might not reach the shore, let alone flood the land. The 1607 event shows that these unfortunate coincidences do occur and for this reason the Bristol Channel coast, as well as all coasts everywhere, should be protected by a tsunami warning system.
Without such a warning system, people living in low-lying coastal areas should go upstairs, or climb a tree, if they feel an earth tremor or see the sea rise or rush out suddenly, as research has shown that many stone buildings and trees withstand all but the biggest tsunami. Stay up off the ground for at least a few hours as it is likely that more than one tsunami wave will strike, the second or third wave often being higher than the first.
Dr Simon Haslett is Head of the Dept. of Geography at Bath Spa University College, a Fellow of the Royal Geographical Society, and author of the book Coastal Systems (Routledge London)
Original Content can be found Here.
Somerset Genealogy.
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