Bristol Channel Tsunami?!!, 1607

On 30 January 1607 the Bristol Channel floods resulted in the drowning of an estimated 2,000 or more people, with houses and villages swept away, an estimated 200 square miles (518 km2) of farmland inundated and livestock destroyed, wrecking the local economy along the coasts of the Bristol Channel, UK.

The devastation was particularly bad on the Welsh side from Laugharne in Carmarthenshire to above Chepstow on the English border. Cardiff was the most badly affected town. The coasts of Devon and the Somerset Levels as far inland as Glastonbury Tor, 14 miles (23 km) from the coast, were also affected.

There remain plaques up to 8 feet (2 m) above sea level to show how high the waters rose on the sides of the surviving churches. It was commemorated in a contemporary pamphlet God's warning to the people of England by the great overflowing of the waters or floods.

Possible causes

The cause of the flood remains disputed insofar as contemporary 'explanations' blamed God then scientific explanations ignored much of the written evidence and blamed bad weather, until recent research suggested a tsunami. Traditionally it had long been believed that the floods were caused by a combination of meteorological extremes and a known unusually high tidal peaks when a storm surge (flood) hit the shores of the channel.

However a research paper published in the journal Archaeology in the Severn Estuary in 2002 following investigations by Professor Simon Haslett, from Bath Spa University, and Australian geologist Ted Bryant, from the University of Wollongong, proposed that the flooding was caused by a tsunami.

The BBC made a programme exploring the theory (The Killer Wave of 1607) as part of the Timewatch series. Although made prior to the 2004 tsunami disaster, it was not broadcast until 2 April 2005 and repeated on 24 January 2007. The timing of the initial broadcast led some to suggest, wrongly, that the notion of a tsunami in 1607 was simply speculation following the 2004 tsunami disaster. On the 400th anniversary (30 January 2007), BBC Somerset looked at the possible causes and asked whether it could it happen again in the county.

The British Geological Survey has suggested that as there is no evidence of a landslide off the continental shelf, a tsunami would most likely have been caused by an earthquake on a known unstable fault off the coast of Ireland, causing the vertical displacement of the sea floor.

 

Evidence

Haslett and Bryant found evidence including massive boulders that had been displaced up the beach by enormous force; a layer up to 8 inches (20 cm) thick composed of sand, shells and stones within an otherwise constant deposit of mud that was found in boreholes from Devon to Gloucestershire and the Gower peninsula; and rock erosion characteristic of high water velocities throughout the Severn Estuary.

Written evidence from the time describes events that were uncannily similar to the tragedies that unfolded in South East Asia, including a wave of water that rushed in faster than men could run, a crowd of people who stood and watched the wave coming towards them until it was too late to run, and the sea receding before the wave arrived.

However, there are also similarities to descriptions of the 1953 floods in East Anglia, which was caused by a storm surge. Also, the original sources frequently refer to the high spring tide and strong winds from the south west - classic conditions for a storm surge. Horsburgh and Horritt have shown that the tide and probable weather at the time were capable of generating a surge that is totally consistent with the observed inundation. Furthermore, the same original sources make it clear that flooding occurred in Norfolk on the night of the same date (at local high water). There is no plausible candidate tsunami that can affect the Bristol Channel and also propagate into the North Sea with any significant amplitude.

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