Bristol Channel floods, 1607
On 30 January 1607, around noon, the coasts of the Bristol Channel suffered from unexpectedly high floodings that broke the coastal defences in several places. Low-lying places in Devon, Somerset, Gloucestershire, and South Wales were flooded. The devastation was particularly severe on the Welsh side, extending from Laugharne in Carmarthenshire to above Chepstow in Monmouthshire. Cardiff was the most badly affected town, with the foundations of St Mary's Church destroyed.
It is estimated that 2,000 or more people were drowned, houses and villages were swept away, an estimated 200 square miles (51,800 ha) of farmland inundated, and livestock destroyed, wrecking the local economy along the coasts of the Bristol Channel and Severn Estuary.
The coast of Devon and the Somerset Levels as far inland as Glastonbury Tor, 14 miles (23 km) from the coast, were also affected. The sea wall at Burnham-on-Sea gave way, and the water flowed over the low-lying levels and moors. Thirty villages in Somerset were affected, including Brean which was "swallowed up" and where seven out of the nine houses were destroyed with 26 of the inhabitants dying. For ten days the Church of All Saints at Kingston Seymour, near Weston-super-Mare, was filled with water to a depth of 5 feet (1.5 m). A chiselled mark remains showing that the maximum height of the water was 7.74 metres above sea level.
A number of commemorative plaques still remain, up to 8 feet (2 m) above sea level, showing how high the waters rose on the sides of surviving churches. For example at Goldcliff near Newport the church has a small brass plaque, inside on the north wall near the altar, today about three feet above ground level, marking the height of the flood waters. The plaque records the year as 1606 because, under the Julian calendar in use at that time, the new year did not start until Lady Day, 25 March. The estimate of resultant financial loss in the parish is given as approximately £5,000 (equivalent to £970,000 in 2015).
The cause of the flood is not definitively known. Contemporary explanations blamed God. Subsequent scientific explanations ignored much of the written evidence and blamed a storm surge, a combination of meteorological extremes and a high tide, until research in 2002 suggested a tsunami.
Written evidence from the time describes events that were similar to those that unfolded in the 2004 Indian Ocean earthquake and tsunami, including the sea receding before the wave arrived, a wave of water that rushed in faster than men could run, a description of the waves as "dazzling, fiery mountains", and a crowd of people who stood and watched the wave coming towards them until it was too late to run. Some of the most detailed accounts also state that it had been a sunny morning.
A 2002 research paper, following investigations by Professor Simon Haslett of Bath Spa University and Australian geologist Ted Bryant of the University of Wollongong, suggested that the flooding may have been caused by a tsunami, after the authors had read some eyewitness accounts in the historical reports which described the flood.
A BBC programme exploring the theory, The Killer Wave of 1607, was made as part of the Timewatch series. Although made prior to the 2004 tsunami disaster, it was not broadcast until 2 April 2005, was repeated on 24 January 2007 and 16 April 2017.
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. One contemporary report describes an earth tremor on the morning of the flood.
Haslett and Bryant found significant evidence for the tsunami hypothesis. This included 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.
Storm surge hypothesis
There are similarities to descriptions of the 1953 floods in East Anglia which were caused by a storm surge. Some of the original sources frequently referred to the high spring tide and strong winds from the southwest, 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 consistent with the observed inundation.
While the risk of similar events in the foreseeable future is considered to be low, it is estimated that the potential cost caused by comparable flooding to residential, commercial, industrial, and agricultural property could range from £7 to £13 billion at 2007 insured values. There has also been concern that the nuclear power stations at Hinkley Point and Oldbury could be endangered.RMS 2007, p. 17
- List of natural disasters in Great Britain and Ireland
- List of disasters in Great Britain and Ireland by death toll
- List of Deadliest Tsunamis
- Geology of Great Britain
- Tsunamis affecting the British Isles
- 1999 Blayais Nuclear Power Plant flood
- Modern sources for this event commonly use the Gregorian calendar, however contemporary records record the event as happening on 20 January 1606/07 under the Julian calendar (see for example the flood plaque, in St Mary's Church pictured on this page where the date is given as 20 January 1606). For a more detailed explanation of these changes in calendar and dating styles, see Old Style and New Style dates.
- Disney, Michael (4 January 2005). "Britain had its own big waves - 400 years ago". The Times. London. Retrieved 20 February 2008. (Subscription required (. ))
- BBC staff (24 September 2014). "The great flood of 1607: could it happen again?". BBC Somerset. Retrieved 20 February 2008.
- "Burnham on Sea". Somerset Guide. Retrieved 10 May 2010.
- Hawkins, Desmond (1982). Avalon and Sedgemoor. pp. 29–30. ISBN 0-86299-016-5.
- 1607 Bristol Channel Floods: 400-Year Retrospective RMS Special Report (PDF). Risk Management Solutions (RMS). 2007. p. 12.
- UK Consumer Price Index inflation figures are based on data from Gregory Clark (2016), "The Annual RPI and Average Earnings for Britain, 1209 to Present (New Series)", MeasuringWorth.com.
- Disney 2005
- "Gods Warning to his people of England.". The British Library. Retrieved 20 February 2008.
- Bryant, Edward; Haslett, Simon (2007). "Catastrophic Wave Erosion, Bristol Channel, United Kingdom: Impact of Tsunami?". Journal of Geology. 115 (3): 253–270. doi:10.1086/512750.
- Bryant, Edward; Haslett, Simon (2002). "Was the AD 1607 Coastal Flooding Event in the Severn Estuary and Bristol Channel (UK) Due to a Tsunami". Archaeology in the Severn Estuary (13): 163–167. ISSN 1354-7089.
- BBC staff (4 April 2005). "Tsunami theory of flood disaster". BBC News Online. Retrieved 13 November 2010.
- "Burnhams 1607 flood to be the focus of BBC documentary". Burnham on Sea.com. Retrieved 20 February 2008.
- BBC staff 2005
- Haslett, Simon K. (2010). Somerset Landscapes: Geology and landforms. Usk: Blackbarn Books. p. 159. ISBN 9781456416317.
- Haslett, Simon; Bryant, Edward (2004). "The AD 1607 Coastal Flood in the Bristol Channel and Severn Estuary: Historical Records from Devon and Cornwall (UK)". Archaeology in the Severn Estuary (15): 81–89. ISSN 1354-7089.
- Bryant & Haslett 2007, pp. 253–270
- Horsburgh, K.J.; Horritt, M. (2006). "The Bristol Channel floods of 1607 – reconstruction and analysis". Weather. 61 (10): 272–277.
- RMS 2007, p. 16
- BBC staff 2014
- "Geology: Ooo arhh! A Tsunami May Have Struck Britain 400 Years Ago". The Economist. 5 May 2007. p. 83.
- Horsburgh, K.J. and M. Horritt (2006), "The Bristol Channel floods of 1607 – reconstruction and analysis". Weather, Royal Meteorological Society, 61(10), 272–277.