Hydrodynamic modelling reveals more about deadly 1607 flood in South West

12 May 2021

The application of refined hydrodynamic modelling techniques to investigate a devastating flood that occurred in Bristol Channel and Severn Estuary in 1607 has led to new findings that will assist local authorities in the region with their risk and hazard management planning.

In 2003, Professor Simon Haslett  (below), Short-Term Visiting Fellow at Jesus College and his co-worker Dr Ted Bryant published their research on the little-known flood, which affected the counties of Devon, Somerset and Gloucestershire in England, and along the South Wales coast, mainly from Monmouthshire to Carmarthenshire.

Man smiling on coast - Prof Simon Haslett

Professor Simon Haslett

 

The paper presented a theory, based on historical documents and physical evidence from the landscape, that questioned whether the catastrophic flood of the 30th January 1607 was due to a tsunami (often in the past referred to as a ‘tidal wave’) rather than to the effects of a storm. From the researchers’ analysis, it appears that the flood resulted in the death of around 2000 inhabitants of an area of coastline approximately 518km2.

Using hydrodynamic modelling at the time, Professor Haslett and Dr Bryant estimated that the wave may have reached up to 6m high in the Severn Estuary and flooded the coastal lowlands at great speed, causing considerable damage and loss of life.

Some 18 years on, Professor Haslett has been revisiting the evidence as part of research he is undertaking at Jesus College. Since 2003, the hydrodynamic modelling has been refined in collaboration with Professor Bernie Wong of the Institute of Mathematical Sciences at the University of Malaya, and newly developed equations permit a recalculation of possible wave heights.

Professor Haslett says, “The new study is in broad agreement with previous work but concludes that a tsunami of just over 4m high is required to explain the evidence, whereas storm waves of around 17m would be required which, in the sheltered Severn Estuary, is unlikely to be the case.“

He adds, “These results shed new light on a devastating tragedy that affected so many people at the time, and we’re delighted that our findings will help to inform local authorities in the Bristol Channel and Severn Estuary region when reviewing their risk and hazard management plans.”

Professor Haslett published his initial findings in a paper that appeared last month in Atlantic Geologyand presented a seminar on his research as part of Jesus College’s 450th anniversary celebrations.

The research review has also led to another new discovery.  Sir John Rhys (below), a former Principal of the College, in his Celtic Folklore book of 1901, referred to the 1607 flood as “an inundation caused by a terrible tidal wave”. Professor Haslett says, “Given that Sir John Rhys would have no doubt have been familiar with reports of the devastating ‘tidal wave’ associated with the eruption of Krakatoa in 1883, which was a tsunami, it is possible that he may be regarded as the first author to suggest that the 1607 flood might have been due to a tsunami rather than a storm.”

Sir John Rhys

 

The 2003 paper attracted considerable media attention and in 2004 filming began to make a BBC2 Timewatch documentary on the topic to inform the public about the forgotten flood. However, shortly after the programme was completed, the devastating Indian Ocean earthquake and tsunami occurred on Boxing Day 2004, which tragically brought the hazard of tsunamis to the World’s attention. The documentary, entitled Killer Wave of 1607, was consequently delayed but eventually first shown in April 2005 but has been re-broadcast on numerous occasions since.