Recalculation of minimum wave heights from coastal boulder deposits in the Bristol Channel and Severn Estuary, UK: implications for understanding the high-magnitude flood event of AD 1607
A high-magnitude coastal flood event catastrophically affected the macrotidal Bristol Channel and Severn Estuary in southwest Great Britain, United Kingdom, on 30th January 1607 causing an estimated 2000 fatalities. Historical and physical evidence has provided a basis for the development of a theory that the flood may have been due to a tsunami rather than a storm. Previous studies have collected field data to test this hypothesis including a dataset of 136 wave-transported boulder clasts that was utilised to estimate minimum wave heights through hydrodynamic equations in 2007, but the dataset has hitherto remained unpublished in full. Since 2007 these equations have undergone refinement and for this paper minimum wave heights were recalculated from boulder measurements using revised hydrodynamic equations and presents the complete dataset for the first time. A recent study claiming that such equations are flawed is considered premature, given ongoing refinements to the equations. The results of the present study indicate that a tsunami 4.2 m high can explain the dislodgement of all boulders measured, equivalent to a storm wave height of 16.9 m, which is considerably greater than observed storm wave heights in the region. An up-channel increase in minimum wave height is also suggested by these data, generally corroborating the 2007 study, which may be due to wave amplification caused by the overall funnel-shape of the embayment. The areas worst affected by the 1607 flood are located in the coastal lowlands of the inner Bristol Channel and Severn Estuary, coinciding with the highest minimum estimated wave heights.
Abad, M., Izquierdo, T., Cáceres, M., Bernárdez, E., and Rodriguez‐Vidal, J. 2020. Coastal boulder deposit as evidence of an ocean‐wide prehistoric tsunami originated on the Atacama Desert coast (northern Chile). Sedimentology, 67, pp. 1505–1528. https://doi.org/10.1111/sed.12570
Allen, J.R.L. and Fulford, M.G. 1992. Romano-British and later geoarchaeology at Oldbury Flats: reclamation and settlement on the changeable coast of the Severn Estuary. Archaeological Journal, 149, pp.82–123. https://doi.org/10.1080/00665983.1992.11078008
Allen, J.R.L. and Rae, J.E. 1987. Late Flandrian shoreline oscillations in the Severn Estuary: a geomorphological and stratigraphical reconnaissance. Philosophical Transactions of the Royal Society of London, B315, pp.185–230. https://doi.org/10.1098/rstb.1987.0007
Anon 1607. Lamentable newes out of Monmouthshire in Wales. Printed for W.W. and are to be solde in Paules Church yarde at the figure of the Grey hound, London.
Barbano, M.S., Pirrotta, C., and Gerardi, F. 2010. Large boulders along the south-eastern Ionian coast of Sicily: Storm or tsunami deposits? Marine Geology, 275, pp. 140–154. https://doi.org/10.1016/j.margeo.2010.05.005
Barnes, J. 2020. 'God's warning to his people': The day a tsunami hit Gwent. South Wales Argus, 21 November 2020. URL <https://www.southwalesargus.co.uk/news/18888412.gods-warning-people-day-tsunami-hit-gwent/>, February 2021.
Bourgeois, J. and MacInnes, B. 2010. Tsunami boulder transport and other dramatic effects of the 15 November 2006 central Kuril Islands tsunami on the island of Matua. Zeitschrift für Geomorphologie (Supplement), 54, pp. 175–195. https://doi.org/10.1127/0372-8854/2010/0054S3-0024
Bryant, E.A. and Haslett, S.K. 2003. 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, pp. 163–167.
Bryant, E.A. and Haslett, S.K. 2007. Catastrophic wave erosion, Bristol Channel, United Kingdom: impact of tsunami? Journal of Geology, 115, pp. 253–269. https://doi.org/10.1086/512750
Costa, P.J., Andrade, C., Freitas, M.C., Oliveira, M.A., da Silva, C.M., Omira, R., Taborda, R., Baptista, M.A., and Dawson, A.G. 2011. Boulder deposition during major tsunami events. Earth Surface Processes and Landforms, 36, pp. 2054–2068. https://doi.org/10.1002/esp.2228
Cox, R., Jahn, K.L., Watkins, O.G., and Cox, P. 2018. Extraordinary boulder transport by storm waves (west of Ireland, winter 2013–2014), and criteria for analysing coastal boulder deposits. Earth-Science Reviews, 177, pp. 623–636. https://doi.org/10.1016/j.earscirev.2017.12.014
Cox, R., Ardhuin, F., Dias, F., Autret, R, Beisiegel, N., Earlie, C.S., Herterich, J.G., Kennedy, A., Paris, R., Raby, A., Schmitt, P., and Weiss, R. 2020. Systematic review shows that work done by storm waves can be misinterpreted as tsunami-related because commonly used hydrodynamic equations are flawed. Frontiers in Marine Science, 7. https://doi.org/10.3389/fmars.2020.00004
Disney, M. 2005a. Britain had its own big wave – 400 years ago: an Atlantic tsunami created our greatest environmental disaster, and it could happen again. The Times (London), 4 January, p. 11.
Disney, M., 2005b. When a wave almost washed away Cardiff. Western Mail, 5 January, p. 8.
Erdmann, W., Kelletat, D., Scheffers, A., and Haslett, S. K. 2015. Origin and Formation of Coastal Boulder Deposits at Galway Bay and the Aran Islands, Western Ireland. Springer Briefs in Geography, 125 pp. https://doi.org/10.1007/978-3-319-16333-8
Erdmann, W., Kelletat, D., and Kuckuck, M. 2017. Boulder ridges and washover features in Galway Bay, Western Ireland. Journal of Coastal Research, 33, pp. 997–1021. https://doi.org/10.2112/JCOASTRES-D-16-00184.1
Gandhi, D., Chavare, K. A., Prizomwala, S. P., Bhatt, N., Bhatt, N. Y., Mohan, K., and Rastogi, B. K. 2017. Testing the numerical models for boulder transport through high energy marine wave event: an example from southern Saurashtra, Western India. Quaternary International, 444, pp.209–216. https://doi.org/10.1016/j.quaint.2016.05.021
Goto, K., Okada, K., and Imamura, F. 2009. Characteristics and hydrodynamics of boulders transported by storm waves at Kudaka Island, Japan. Marine Geology, 262, pp. 14–24. https://doi.org/10.1016/j.margeo.2009.03.001
Goto, K., Miyagi, K., Kawamata, H., and Imamura, F. 2010. Discrimination of boulders deposited by tsunamis and storm waves at Ishigaki Island, Japan. Marine Geology, 269, pp. 34–45. https://doi.org/10.1016/j.margeo.2009.12.004
Hansom, J. D., Barltrop, N.D.P., and Hall, A.M. 2008. Modelling the processes of cliff-top erosion and deposition under extreme storm waves. Marine Geology, 253, pp. 36–50. https://doi.org/10.1016/j.margeo.2008.02.015
Haslett, S. K. 2007. 400 years on! Report of a public conference commemorating the 400th anniversary of the 1607 flood in the Bristol Channel and Severn Estuary, UK. Archaeology in the Severn Estuary, 18, pp. 115–118.
Haslett, S. K. 2011. Earthquakes, tsunami and nuclear power: relevance of the 1607 flood in the Bristol Channel. Blackbarn Books, UK, 26 p.
Haslett, S. K. and Bryant, E. A. 2005. 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 (for 2004), pp. 81–89.
Haslett, S. K. and Bryant, E. A. 2007a. Evidence for historic coastal high-energy wave impact (tsunami?) in North Wales, United Kingdom. Atlantic Geology, 43, pp. 137–147. https://doi.org/10.4138/4215
Haslett, S. K. and Bryant, E. A. 2007b. Reconnaissance of historic (post-AD 1000) high-energy deposits along the Atlantic coasts of southwest Britain, Ireland and Brittany, France. Marine Geology, 242, pp. 207–220. https://doi.org/10.1016/j.margeo.2007.01.011
Haslett, S. K. and Bryant, E. A. 2009. Meteorological tsunami in southern Britain: an historic review. Geographical Review, 99, pp. 146–163. https://doi.org/10.1111/j.1931-0846.2009.tb00424.x
Haslett, S. K. and Wong, B. R. 2019a. An evaluation of boulder deposits along a granite coast affected by the 2004 Indian Ocean tsunami using revised hydrodynamic equations: Batu Ferringhi, Penang, Malaysia. Journal of Geology, 127, pp. 527–541. https://doi.org/10.1086/704255
Haslett, S.K. and Wong, B.R. 2019b. Reconnaissance survey of coastal boulders in the Moro Gulf (Philippines) using Google Earth imagery: Initial insights into Celebes Sea tsunami events. Bulletin of the Geological Society of Malaysia, 68, pp. 37–44. https://doi.org/10.7186/bgsm68201903
Heezen, B.C. and Ewing, W.M. 1952. Turbidity currents and submarine slumps, and the 1929 Grand Banks earthquake. American journal of Science, 250, pp. 849–873. https://doi.org/10.2475/ajs.250.12.849
Horsburgh, K. and Horritt, M. 2006. The Bristol Channel floods of 1607–reconstruction and analysis. Weather, 61, pp. 272–277. https://doi.org/10.1256/wea.133.05
Kain, C.L., Gomez, C., and Moghaddam, A.E. 2012. Comment on ‘Reassessment of hydrodynamic equations: Minimum flow velocity to initiate boulder transport by high energy events (storms, tsunamis) by N.A.K. Nandasena, R. Paris and N. Tanaka [Marine Geology 281, 70–84]. Marine Geology, 319, pp. 75–76. https://doi.org/10.1016/j.margeo.2011.08.008
Kennedy, A.B., Mori, N., Yasuda, T., Shimozono, T., Tomiczek, T., Donahue, A., Shimura, T. and Imai, Y. 2017. Extreme block and boulder transport along a cliffed coastline (Calicoan Island, Philippines) during Super Typhoon Haiyan. Marine Geology, 383, pp.65–77. https://doi.org/10.1016/j.margeo.2016.11.004
Kenyon, N.H. 1987. Mass-wasting features on the continental slope of northwest Europe. Marine Geology, 74, pp. 57–77. https://doi.org/10.1016/0025-3227(87)90005-3
Kerridge, D. 2005. The threat posed by tsunami to the UK. Department for Environment, Food and Rural Affairs, HMSO, 123 pp.
Lorang, M.S. 2011. A wave-competence approach to distinguish between boulder and megaclast deposits due to storm waves versus tsunami. Marine Geology, 283, pp. 90–97. https://doi.org/10.1016/j.margeo.2010.10.005
McLaren, P., Collins, M.B.; Gao, S., and Powys, R.I.L. 1993. Sediment dynamics of the Severn Estuary and inner Bristol Channel. Journal of the Geological Society, London, 150, pp. 589–603. https://doi.org/10.1144/gsjgs.150.3.0589
Moore, A.L., McAdoo, B.G., and Ruffman, A. 2007. Landward fining from multiple sources in a sand sheet deposited by the 1929 Grand Banks tsunami, Newfoundland. Sedimentary Geology, 200, pp. 336–346. https://doi.org/10.1016/j.sedgeo.2007.01.012
Nandasena, N.A.K., Paris, R., and Tanaka, N. 2011. Reassessment of hydrodynamic equations: minimum flow velocity to initiate boulder transport by high energy events (storms, tsunamis). Marine Geology, 281, pp. 70–84. https://doi.org/10.1016/j.margeo.2011.02.005
NERC 1991. United Kingdom digital marine atlas. Natural Environment Research Council for Great Britain, Swindon.
Nott, J. 1997. Extremely high-energy wave deposits inside the Great Barrier Reef, Australia: determining the cause—tsunami or tropical cyclone. Marine Geology, 141, pp. 193–207. https://doi.org/10.1016/S0025-3227(97)00063-7
Nott, J. 2003. Waves, coastal boulder deposits and the importance of the pre-transport setting. Earth and Planetary Science Letters, 210, pp. 269–276. https://doi.org/10.1016/S0012-821X(03)00104-3
Paris, R., Naylor, L.A., and Stephenson, W.J. 2011. Boulders as a signature of storms on rock coasts. Marine Geology, 283, pp. 1–11. https://doi.org/10.1016/j.margeo.2011.03.016
Piper, D.J., Cochonat, P., and Morrison, M.L. 1999. The sequence of events around the epicentre of the 1929 Grand Banks earthquake: initiation of debris flows and turbidity current inferred from sidescan sonar. Sedimentology, 46, pp. 79–97. https://doi.org/10.1046/j.1365-3091.1999.00204.x
Piscitelli, A., Milella, M., Hippolyte, J.C., Shah-Hosseini, M., Morhange, C., and Mastronuzzi, G. 2017. Numerical approach to the study of coastal boulders: The case of Martigues, Marseille, France. Quaternary International, 439, pp.52–64. https://doi.org/10.1016/j.quaint.2016.10.042
Scheffers, A., Scheffers, S., Kelletat, D., and Browne, T. 2009. Wave-emplaced coarse debris and megaclasts in Ireland and Scotland: boulder transport in a high-energy littoral environment. Journal of Geology, 117, pp. 553–573. https://doi.org/10.1086/600865
Scheffers, A., Kelletat, D., Haslett, S., Scheffers, S., and Browne, T. 2010. Coastal boulder deposits in Galway Bay and the Aran Islands, western Ireland. Zeitschrift für Geomorphologie (Supplement), 54, pp. 247–279. https://doi.org/10.1127/0372-8854/2010/0054S3-0027
Skellern, A.R., Haslett, S.K., and Open, S.P. 2008. The potential area affected by the 1607 flood event in the Severn Estuary, UK: a preliminary investigation. Archaeology in the Severn Estuary, 18, pp. 59–65.
Spiske, M., Böröcz, Z., and Bahlburg, H. 2008. The role of porosity in discriminating between tsunami and hurricane emplacement of boulders—a case study from the Lesser Antilles, southern Caribbean. Earth and Planetary Science Letters, 268, pp. 384–396. https://doi.org/10.1016/j.epsl.2008.01.030
Stephenson, W.J. and Naylor, L.A. 2011. Geological controls on boulder production in a rock coast setting: insights from South Wales, UK. Marine Geology, 283, pp.12–24. https://doi.org/10.1016/j.margeo.2010.07.001
Switzer, A.D. and Burston, J.M. 2010. Competing mechanisms for boulder deposition on the southeast Australian coast. Geomorphology, 114, pp. 42–54. https://doi.org/10.1016/j.geomorph.2009.02.009
Watanabe, M., Goto, K., Imamura, F., and Hongo, C. 2016. Numerical identification of tsunami boulders and estimation of local tsunami size at Ibaruma reef of Ishigaki Island, Japan. Island Arc, 25, pp. 316–332. https://doi.org/10.1111/iar.12115
Zingg, T. 1935. Beitrage zur Schotteranalyse. Schweizerische Mineralogische und Petrographische Mitteilungen, 15, pp. 38–139.
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