School of
Science and the Environment
PRESS RELEASE
Tsunami in the Bristol Channel and Severn Estuary in 1607
Research into the devastating coastal flood event that affected the Bristol
Channel and Severn Estuary in January 1607 has, since 2002, been the
subject of collaborative study between:
 Dr Simon Haslett, Head of Geography at Bath Spa University College,
author of Coastal Systems (Routledge) and
 Dr Ted Bryant, School of Geosciences at the University of Wollongong,
Australia, author of Tsunami: the Underrated Hazard (Cambridge
University Press)
The flood occurred around 9am on the '20th January 1606', although in the
modern calendar this is the 30th January 1607. The event is recorded on
plaques in a number of churches, including those at Kingston Seymour in
Somerset, and in Monmouthshire at Goldcliff, St. Brides, Redwick and
Peterstone.
The Kingston Seymour plaque reads:
"An inundation of the Sea-water by overflowing and breaking down the
Sea banks; happened in this Parish of Kingstone-Seamore, and many
others 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. WILLIAM
BOWER"
The idea that the 1607 flood was due to a tsunami was first put forward by
Haslett and Bryant in a scientific paper published in 2002 in the journal
Archaeology in the Severn Estuary.
A number of historical documents exist that describe the event and its
aftermath. An area from Barnstaple in north Devon, up the Bristol Channel
and Severn Estuary to Gloucester, then along the South Wales coast around
to Cardigan was affected, some 570 km of coastline.
The coastal population was devastated with at least 2000 fatalities according
to one of the contemporary sources. In some parts of the coast the population
never recovered from the social and economic disaster.
1
Examples of the human tragedy include:








At Appledore, Devon, a 60 tonne ship was well-laden and ready to sail
and was driven by the wave onto marshy ground well above high tide,
likely never to be recovered.
In Barnstaple, Devon, the wave burst open doors that were locked and
bolted and knocked down many walls and houses, one of which was the
house of a James Frost in that the roof and walls collapsed and killed
both him and two of his children.
Near Newport, Gwent, a wealthy women, Mistress Van, lived four miles
from the sea and although she saw the wave approaching from her
house she could not get upstairs before it rushed through and drowned
her.
In Monmouthshire, "a maide child, not passing the age of foure years: it
is reported that the mother thereof, perceiving the waters to breake so
fast into her house, and not being able to escape with it, and having no
clothes on, set it upon a beame in the house, to save it from being
drowned. And the waters rushing in a pace, a little chicken as it
seemeth, flew up unto it [the child], (it being found in the bosome of it,
when helpe came to take it [the child] downe) and by the heate thereof,
as it is thought, preserved the childe's life".
In Monmouthshire, "Another little childe is affirmed to have been cast
uppon land in a cradle, in which was nothing but a catte [cat], the which
was discerned as it came floating to the shoare, to leape still from one
side of the cradle unto the other, even as if she had been appointed
steresman to preserve the small barke from the waves furie".
In Monmouthshire, "A certain man and woman having taken a tree for
their succour, espying nothing but death before their eyes, at last among
other things which were carried along, they perceived a certain tubbe of
great bignesse to come nearer and nearer unto them, until it rested upon
that tree wherein they were, committed themselves, and were carried
safe until they were cast upon the drie shore".
In Monmouthshire, "more than did, had perished for want of food, and
extreme cold, had not the Rt. Honble. Lord Herbert .... sent out boats to
relieve the distresse .... himself goping to such houses as he could
minister to their provision of meate and other necessaries".
In Somerset, through the breaking of the sea bank at Burnham some 30
villages were utterly inundated, and their cattle destroyed, and men,
women and children besides. The accounts state that 28 people were
drowned at Huntspill and 26 at Brean, and death toll that was similar in
many other villages.
Haslett and Bryant were led to think that the 1607 flood was caused by a
tsunami, rather than a storm, for a number of reasons:
 Some historical accounts indicate that the weather was fine e.g. "for
about nine of the morning, the same being most fayrely and brightly
spred, many of the inhabitants of these countreys prepared themselves
to their affayres" and the ship at Appldedore (see above) is unlikely to be
ready to sail in stormy weather.
2

The sea appears to have been "driven back" i.e. retreated out to sea,
before the wave struck, a classic tsunami herald.
 The wave appeared as " mighty hilles of water tombling over one
another in such sort as if the greatest mountains in the world had
overwhelmed the lowe villages or marshy grounds Sometimes it dazzled
many of the spectators that they imagined it had bin some fogge or mist
coming with great swiftness towards them and with such a smoke as if
mountains were all on fire, and to the view of some it seemed as if
myriads of thousands of arrows had been shot forth all at one time". This
is very similar to descriptions of more recent tsunami, such as the
tsunami associated with the eruption of Krakatau in 1883, where
accounts refer to the sea as being ‘hilly’, and the reference to dazzling,
fiery mountains, and myriads of arrows, is reminiscent of accounts of
tsunami on the Burin Peninsula (Newfoundland) in 1929, where the
wave crest was shining like car headlights, and in Papua New Guinea in
1998 where the wave was frothing and sparkling. Film of the Asian
tsunami is similar.
 The speed of the wave appears to have been faster than a storm flood
as the wave is ‘affirmed to have runne …. with a swiftness so incredible,
as that no gray-hounde could have escaped by running before them’.
In the summer of 2004, Haslett and Bryant embarked on field work in the area
to record any physical impacts of the proposed 1607 tsunami that might still
be left in the landscape. They found:
 erosion of rock at the coast that is characteristic of erosion caused by
high velocity water flow. This includes two large chunks of farmland on
the Severn Estuary north of Bristol that were simply washed away, one
where the foundation of the Second Severn Crossing is, and the other is
now the reservoir for the Oldbury Nuclear Power Station;
 the deposition of layers of sand over wide areas at the time, discovered
in boreholes in the ground from north Devon to Gloucestershire to the
Gower;
 large boulders that are only easily moved by tsunami waves have been
found stacked like dominoes at and above the high tide limits all along
the coast.
These signatures of tsunami enable Haslett and Bryant to estimate the scale
of the proposed tsunami wave and its affects.
Tsunami height - In the open sea area between north Devon and
Pembrokeshire, the wave was just under 4m (13ft) high, but as it entered the
constricting funnel-shaped Bristol Channel and Severn Estuary, the wave
increased in height to 5m (16ft) along the Glamorgan coast, 5.5m (18ft) along
the Somerset coast, and over 7.5m (25ft) high, by the time it reached the
Monmouthshire coast. This increase in wave height due to the funnel-shape
of the estuary is exactly the same as the process that creates the famous
Severn Bore.
Tsunami speed - The speed (velocity) of a tsunami is related to its height, so
as it moved up estuary and got squeezed between the opposing shores of
England and Wales, it got faster, striking the coast at just over 12 m/sec
3
(27mph) in north Devon and southwest Wales, to just under 14 m/sec
(31mph) along the Glamorgan coast, to 14.5 m/sec (32mph) in Somerset, and
over 17 m/sec (38mph) in Monmouthshire. This agrees well with the
contemporary observations regarding the speed of the wave.
Tsunami inundation - On the flat coastal areas the tsunami was able to
penetrate a considerable distance inland. The maximum inland penetration
possible of a moving tsunami wave in north Devon and southwest Wales
would have been just under 2.5 km (1.55 miles), in Glamorgan just over 3 km
(1.86 miles), in Somerset just under 4 km (2.5 miles), and in Monmouthshire
just under 6 km (3.7 miles). This agrees well with the accounts of the wave
reaching up to 4 miles inland at Cardiff and in Monmouthshire. The fact that
the floodwaters reached further inland in places, such as to the foot of
Glastonbury Tor (14 miles inland) is due to the fact that the landsurface
actually slopes landward in many of the coastal wetland areas, such as the
Somerset Levels, so once the wave collapsed the water flowed landward
under gravity rather than back to the sea.
A possible cause of the proposed tsunami is not yet known, but the
possibilities include a submarine landslide off the continental shelf between
Ireland and Cornwall, or an earthquake along an active fault system in the sea
south of Ireland. This fault system has apparently experienced an earthquake
greater than magnitude 4 on the Richter scale within the last 20 years, so the
chance of a bigger tsunami earthquake is a possibility. It may also have been
a combination, in that an earthquake might have triggered a submarine slide.
A BBC Timewatch programme was filmed in the summer of 2004 in
conjunction with Haslett and Bryant's research and fieldwork, and is
scheduled to be shown early in 2005, although some re-editing may be
needed in response to the Asian tsunami.
For further information, please contact:
Dr Simon Haslett FGS, FRGS
Dept. of Geography,
School of Science and the Environment,
Bath Spa University College,
Newton Park,
Bath, BA2 9BN.
Tel: 01225 875544 (or 01225-875585)
Email: s.haslett@bathspa.ac.uk
4