All language subtitles for britains.killer.wave.of.1607.2024.1080p.web.h264-cbfm_track3_[eng]

SAMANTHA BOND:
Extreme weather events

can be shockingly destructive.

From the Great Storm of 1987,
and the Big Freeze of 1963,

to the devastating London floods
of 1928.

But perhaps the biggest
and most shocking

weather disaster to hit Britain
came in January 1607,

in the form of huge tidal waves.

WOMAN: The water that came in
was tremendous.

There's no two ways about it.

They travelled the length of the
Bristol Channel and Severn Estuary,

killing hundreds of people,

taking out buildings
and devastating villages.

We should acknowledge
as the single greatest

destructive event
in Barnstable's history.

In this programme,

we tell the story
of the great tidal waves

hour by hour and,
using historical documents,

recount just how destructive
they were.

This is the worst flood in the last
thousand years in the Severn.

But one important question remains:

Just what caused
this terrible disaster?

The early 1600s were a time of
great change for England and Wales.

In 1603, the Scottish James VI

had become James I
of England and Wales,

the beginning of the Stuart era.

1607 will see the first permanent
English settlement

established in the New World -

Jamestown, named after the king.

But despite all this change
and expansion,

for many people, existence continues
as it has for centuries.

CHILD LAUGHS

But life is fragile.

The whole of the early-modern
pre-modern world,

people live in a world in which the
chance of dying is very, very high.

So if you lived
in an early-modern city,

plague outbreaks might come along
every 10, 20 years

and kill vast numbers of people.

Communities, societies, economies

have to be able to roll
with the punches

cos the punches
are coming constantly.

Most people outside the cities
work in agriculture

and will be born, work, grow old,
and die in the same village or town.

Also in 1607,
an extreme weather event

will hit England and Wales

so powerful that it will devastate
whole communities.

By the end of January 1607,

there has been a six-week-long
warm and wet spell

creating perfect conditions
for storms.

Powerful south-westerly winds

have been battering the vulnerable
Cornish coast for days.

And today, the 30th of January,

the locals are expecting one
of the highest tides of the year...

..but they have no idea of the
extent of what's heading for them.

During the night,

the people at the prosperous
port town of Barnstaple

have noticed a violent storm
out at sea.

The parish clerk
wrote in the parish register

that the storm started
at 3:00 in the morning.

They were certainly aware of a storm
that was remarkable,

remarkable enough to get a...

People must have woken up.

Six miles away, right on the coast,
is Appledore.

In 1607, it was a tiny fishing port
with a small population,

where the rivers Taw and Torridge
poured into the Bristol Channel.

It's a dark, cold winter morning,

so I would've expected
at three to four in the morning

people were still in bed.

They would have been aware of it

by their shutters rattling
outside their windows.

They would have heard the wind
whistling down their chimneys.

They would have been quite worried.

Then, as dawn is approaching...

..huge waves start
hitting the village of Appledore.

With the simple-structured buildings
giving no resistance

to the force of water
and with no sea defence walls,

huge waves raced through the narrow
streets and engulfed the town.

But the waves are carrying something
even more dangerous.

As the tide comes in,

a 60-ton laden ship

was pushed inland
quite some distance

by the weight of the water,
by the force of the water.

After flooding Appledore,

the waves head up the River Taw
at incredible speed.

They travel six miles,
past farmland and homes,

straight towards the flourishing
market town of Barnstaple.

In 1607,

Barnstaple is considered
a wealthy little town.

Fashionable,

the houses are full
of spectacular plaster ceilings,

wonderful carved rooms.

This was a content
and agreeable place to be.

Barnstable is a popular,
thriving market town,

home to hundreds of people.

A busy economic hub in 1607,
people's livelihoods are at risk.

With the rise in international trade
to the Americas,

Barnstable's position
on the North Devon coast

meant it was becoming
an important port.

They were building
all along The Strand

as part of this general expansion
of the quay area.

It's around 7:30am,

and some residents
are still sleeping.

The waves sweep in and wreak havoc

on the building works
along the quay.

We have a tidal river.

Tide comes in, goes out twice a day.

They're used to that,

but they're not used
to a great surge.

They're not used to waves coming in.

And they know, particularly
if they're down by the quays,

that, you know,
they're incredibly vulnerable.

The home of the Frost family
is right at the water's edge.

People try and escape
as best they can,

but as it's early morning,
some are caught unawares.

WOMAN SCREAMS

People died at Barnstable.

GIRL SOBS

The walls being destroyed,
so the roof fell down.

A man and his two daughters.

A contemporary account
gives us the names of those killed.

The death of one James Frost
and two of his children,

in which his house fell down
upon them and killed them.

The parish register names his
daughters as Sabine and Catherine.

For Barnstable...

the thing which gave them
their prosperity,

the sea,
suddenly turns against them.

These huge waves have already
flooded nearby Appledore.

With Barnstable's waterfront
in ruins,

the waves are now heading
straight into the town.

SAMANTHA BOND:
It's the early morning

of the 30th of January, 1607.

Huge waves have hit the ports
of Appledore and Barnstable

on the North Devon coast.

The surge of water
has swept six miles inland

and has destroyed buildings
along the riverside,

killing three people instantly.

WOMAN SCREAMS

Now the waves are pushing water up,

into the narrow streets
of Barnstaple.

The storm not only hits the whole
riverside and goes into the town,

but it overwhelms
what little defences they had.

Robert Langdon, the parish clerk,
recorded the event.

LANGDON: "There was such a mighty
storm and tempest

"from the river of Barnstable,
with the coming of the tide,

"that it caused much loss
of goods and houses."

It goes up the lower part

of what's now High Street
at South Gate.

It goes up Crock Street
and Maiden Lane or Maiden Street.

It goes up a lot further than
they had expected a flood would go.

Barnstable's a low-level place,

you know,
the town doesn't have a hill,

and the water sweeps in
and stretches up into the streets.

It's five to six feet higher,
the water level,

than it is normally.

There's a lot of damage
to the buildings, to the quay area.

We can see in the maps
that they have defensive structures

built around that side of the town,

but they're not good enough
for what is the highest flood

that anybody has ever seen
at that time.

The waters reach all the way
into the town,

but stop short of St Peter's Church
and St Anne's Chapel

right in the centre,

which means the waves
have forced water

around a hundred yards
from the river's edge.

And those buildings are saved.

It's all the buildings
around the quay area,

around the river
in the lower part of town

which are particularly... affected.

The prosperity was all about
access to the sea,

and this flood strikes at that,

because the very thing which gives
them their wealth takes it away.

It's from the town clerk
that we get much of our information

about the effects of the flood.

Thanks to a remarkable discovery
Todd Gray made a few years ago,

The Lost Chronicle of Barnstable,
written by clerk Adam Wyatt.

In Barnstable,
we have the town clerk...

..responsible for the day-to-day
care of Barnstable.

He realises he needs a record
of what happened.

And the flood is an event

which is unlike anything
that they've experienced before,

so it gets a lot of attention.

His account paints a vivid picture
of the flood.

"There was such a flood or tide

"as the like was never seen
in this town.

"It came into all the houses
and cellars near the quay

"with such a power
that it burst open doors

"that were locked and bolted,

"and threw down many houses
and walls.

"Thus the town hath lost in salt,
sugar, woad to the value of £1,000."

That's the equivalent of around
a quarter of a million pounds today,

a huge sum for such a small town.

An account written
a few years later says...

"It subverted houses,
drowned beasts,

"and destroyed people,
of whom some, to save their lives,

"were constrained
from their upper rooms

"to take boat and be gone."

The flood, you know, we should...

acknowledge as the single greatest
destructive event

in Barnstable's history.

Before the horrors of this morning,

Barnstable was a prosperous town
with a bright future.

But all of this new development
is now in ruins.

Just before sunrise,
in the space of a few minutes,

a community has been devastated.

But the waves
are only just getting started.

They are now heading
for one of the world's

most remarkable stretches of water,

and the people
that live alongside it.

The Severn Estuary is one
of the wonders of the British Isles.

It's a powerful body of water

exposed to the full might
of the Atlantic Ocean.

Its special geography is what
will make this flood so devastating.

The Severn Estuary
is quite a unique place.

We have the third highest
tidal range in the world.

The tidal range is something
like 33 foot in places. That's huge.

So it's quite a hostile environment.

The Bristol Channel
is this perfect funnel shape.

So what happens is as the water
is coming in and pushing in,

the shallow depth
and the funnel shape of the land

will compress the water

and push it up
towards the River Severn.

That constriction will then make
the wave more powerful.

If you kind of imagine
like a bellows.

You push it,

then there's a huge kind of shaft
of air which comes out.

Whenever the tide comes in,
it's like this sort of bellows.

But if you then combine that

with a powerful Atlantic
weather system coming in

with a storm coming in
and interrupting it

just the right moment so that
when the bellows goes like that,

it goes...

And suddenly, it's much more
extreme than you expected.

Now around 8am,

the huge waves move up
the Bristol Channel,

reaching the lowlands of Somerset
at incredible speed.

When you come
into the Severn Estuary,

the coastline opens out
into coastal lowlands,

and it's in those low-lying areas

where the full force
of the flood was felt.

Sea walls line the mouth
of the River Parrett at the coast

and should stop the waves
crashing through,

but they were never designed

to protect against something
as big as these waves.

Once the level of water has risen
to the top of those sea walls,

whether it's broken them or not,

it's going to come over
the sea walls

and onto the land behind.

The River Brue that helps drain
the Somerset levels

into the sea also overflows,

flooding a nearby village.

So, in Huntspill, 28 people drowned,

and some of the people in Huntspill

might have tried to make it
to the church.

The church is on a little bit
of higher ground, as you often find.

On the opposite bank
of the River Brue

are Burnham-on-sea and Brent Marsh.

The waves destroy a mile length
of seawall.

People beginning their days

witness a terrifying sight
as the waters flood in.

A news pamphlet of the time
is thought to describe the scene.

MAN: "Many of the spectators that
they imagined it had been some fog

"or mist coming with great swiftness
towards them,

"and with such smoke
as if mountains were all on fire.

"And to the view of some,

"it seemed as if myriads of arrows
had been shot forth

"all at one time."

And the water that came in
was tremendous.

There's no two ways about it.

And so the isolated farmsteads

on Brent Marsh
would have been underwater.

It would have surprised the people.

Clearly, back in 1607,

there was no means of communicating
between the villages and towns,

and people would have been surprised
by it.

It must have been
a terrifying sight.

People wouldn't have known
the sea wall had gone

until they looked out
and found the water was there.

There's a huge difference between
the water coming up sort of so high

and water coming up that high.

You know,
it's the difference between...

having to wade through water
and drown.

Many would have reacted in panic,

desperately trying
to avoid the waves

flowing rapidly over their land.

As they were aware
of water coming in,

they would have looked
to obviously save themselves.

People who died because
they were caught out in a field

and they climbed a tree.

And then, you know,
possibly they died of exposure.

We're obviously in an
agricultural farming community,

so we're dealing with a large
number of beasts and animals

that need some sort of protection
from this water coming in.

It's difficult.

It's difficult for people
to witness and to deal with.

I think it's fair to say
that there would have been

a lot of animals lost.

The waves sweep on.

Within minutes,
they reach the village of Brean,

six miles further up the coast.

The impact is tremendous.

Brean itself
is particularly exposed.

Nine out of the 11 houses
were damaged.

26 people drowned there as well.

News pamphlets published soon after
the disaster described the scene.

MAN: "The forced waters, having
gotten over their wanted limits,

"are affirmed to have run
at their first entrance

"with a swiftness so incredible

"as that no greyhound could have
escaped by running before them."

Farmer John Goode of Brean
loses his wife and nine servants

when the waves strike

but saves himself by clinging on
to a chunk of thatched roof.

It carries him for more than a mile
before washing him up on dry land.

MAN: "Mighty hills of tumbling water
over one another

"in such sort as if
the greatest mountains in the world

"had overwhelmed the low villages
or marshy grounds."

These spectacular waves
that struck at dawn

have battered the English coastline
and flooded huge areas of Somerset.

Whole villages have been devastated.

Farms, homes and livestock
have all been destroyed,

and at least 80 people drowned.

Now at Brean,

only the local church,
the 13th-century Saint Bridget's,

survives of the original village,

keeping its lonely vigil
over the sea.

Almost everything else was destroyed
by the force of the water.

It's now around 8:30am.

The unprecedented waves

have been relentlessly
pushing their way inland,

flooding towns and villages
for more than two hours.

Now they have the vulnerable,
low-lying Gwent levels

on the Welsh coast in their sights.

Like the Somerset levels,

this part of Wales is a large,
isolated area

dotted with small farms
and tiny villages.

Many of the homes
on the low-lying land

are especially vulnerable.

Most of those people who died,

I mean, some died because their
houses were actually washed away.

Houses in this area
may well have been of cob.

Cob is basically mud
mixed with straw,

erm, to stiffen it.

Once a cob building got very wet,
as it would have done with a flood,

it would just crumble away,
really, and be washed away.

People lost their homes
as well as property,

and in many cases, sadly,
their lives.

Many small communities
live right on the coastline.

The communities living
on the Wentlooge level,

at places such as Peterstone
and St Brides Wentlooge,

were right down in the firing line.

There was nowhere else
for them to go to.

The areas which really suffer,

it's not just the countryside,
it's for people on the levels.

The only reason why
they're not flooded constantly

is because they've got
these flood barrier defences.

So that's fine.

But what it means is that
when the water overtops those,

those barriers, then it just...
the water floods in,

and, you know, it's like water
going over the edge of your bath.

It's fine until
it goes over the edge,

and then it causes a terrible mess.

The huge surge of water
shows no signs of relenting

and pushes on
along the Gwent coastline.

After Peterstone,
it washes over St Brides.

We know a little bit more,

perhaps, about St Brides
and what happened there,

because there's a wonderful
stone plaque

in the porch of the church.

And it tells you at the bottom
the height of the flood.

Part of the stone
is sort of crumbling away.

It's a little bit difficult,

but the memory
is the most important thing.

Everybody knows about the flood

because of that particular
inscription.

At Goldcliff,
a mile back from the sea,

there is another plaque.

It states that the water came up
to its level,

that £5,000 worth of damage
was caused and 22 people drowned.

The pamphlet Lamentable Newes
out of Monmouthshire

describes the subversion
of 26 parishes,

which gives a good indication
of how much chaos the waves caused.

In the space of just a few hours,

these massive waves
have devastated whole communities

and changed the landscape forever

and are now heading for
the major port and city of Bristol.

SAMANTHA BOND: It's around 9am
on the 30th of January, 1607.

Mountainous waves are surging

along the Bristol Channel
and Severn Estuary.

After flooding the towns
of Appledore

and Barnstaple in North Devon,
killing three people...

..the tide has pushed
these huge waves

up the low-lying Somerset
and Gwent levels,

killing hundreds of residents
and destroying villages,

farms and isolated homes.

In terms of the Bristol Channel,

we have this sloshing
bathtub effect.

Because of the shape of it,

what will happen is
as the water goes up the channel,

it will bounce from one coastline
to the other.

And that will amplify your wave.

On the English side of the estuary,

the waves are approaching
the city of Bristol,

which lies around eight miles
from the coast,

but the waves don't seem
to be losing momentum.

Bristol, by modern standards,
it was really small,

it was about 12,000 people.

So we kind of think today,
that's really small,

but that still makes it
probably the second

or third largest city in England.

The Avon Gorge connects
the Bristol Channel to the city.

The waves head up this narrow
channel straight for the port.

There was damage to the ports.

We know that warehouses on the quays
would have been also compromised.

The overflowing rivers
Avon and Frome

force water quickly up the streets.

Around five years ago,

Dr Evan Jones,
an expert on the city's history,

discovered something in the Bristol
archives that proved invaluable

in understanding what happens next.

I found this one chronicle
which hadn't been published before,

chronicler, it's a kind of long,
detailed description

of the various things,
the astonishing things.

You know, it's flooding
the whole of central Bristol.

So he talks about how the water rose

as far as the bottom steps
of St Nicholas' crowd door.

He illustrates it by saying that
a bargeman pushed his boat

off the steps
on St Nicholas' Church

and describes the water rising
halfway up the seats

in various churches in the town.

The chronicle says...

MAN: "And in the city of Bristol,

"all the lower part were drowned
about four or five foot.

"The waters were up in
St Stephen's, St Thomas'

"and temple churches
halfway up the seats.

"The merchants received
great losses

"in their storehouses
and cellars by it."

Once again, the very thing
that people relied on

for their livelihoods,
their very lives,

has shown how easily
it can turn against them.

But despite the terror,
the suffering and the destruction,

human bravery prevails.

Around 30 miles from Bristol,

the village of Arlingham
sits on a peninsula

surrounded on three sides
by the Severn.

And when the waves reach up to here,

Arlingham is right
in the firing line.

The water in Arlingham itself,

I think it came up almost
to the cross in Arlingham.

The cross is at the centre
of the village, no longer visible.

The parish records,
written by the vicar,

tell us how this community came
together in the face of catastrophe.

The poor vicar and his wife
and his new baby

lived in practically

the lowest-lying house
in the village.

They were in great peril.

The village keeps a communal boat,
which is used to rescue people

and animals from
the rapidly rising waters.

He wrote in his parish register
that they were among

those 20 or so people
that were rescued by boat...

..and taken up to the church,
up to higher ground.

And he also wrote of those people
that had that not happened,

they might have stived,
ie suffocated or starved to death.

They were cut off, basically.

By around 11am that day,

after five hours
of raging across the landscape,

the waves finally stop.

In Wales,
the floods have reached Chepstow,

where two people are reported
to have drowned.

On the English side,
the waters have reached

over 35 miles north of Bristol.

When it eventually gets up
to Gloucester,

the tide actually starts
to lose its impetus.

So it's still going
to be up high for quite a while,

but it's dropping.

The pamphlet God's Warning
to His People of England says...

MAN: "So violent and swift
were the outrageous waves

"that pursued one another
with such vehemence,

"and the waters multiplying
so much in so short a time,

"that in less than five hours space,
most of the country,

"and especially the places
that laid low, were overflowing."

The news of the sheer size
of the flood

and the devastation it has caused

soon reaches the capital city,
London.

In an age before newspapers,

pamphlets, small documents reporting
news from all over the country,

leap onto the story.

One of our best sources
about the 1607 flood

comes from a series
of four pamphlets

that were published in London,

the first of which probably
was printed around about 17 days

after the event itself.

That news would have had
to have travelled to London,

and the pamphleteers would have
decided what pieces of information,

what intelligence to include.

It's a period you don't get
sort of daily newspapers,

but you are beginning to get
a culture of printers

presenting news pamphlets,

especially relating
to a particular event or happening.

And it's the birth of
kind of cheap popular print.

Along with that,
it's the birth of something

we should maybe recognise today

as almost a kind of
tabloid newspapers

where, you know,
sensational stuff sells,

sort of terrible events sell.

What was particularly remarkable
about this one,

it was one of the first events
where the journalist,

if you want to call them that,
had this really bright idea.

So, this is a pamphlet
which gets produced in London

a few days after the flood.

A true report of certain
wonderful overflowings of water.

Now lately in Somersetshire

and destroying many thousand men
and children

and overflowing and being
whole towns and cities.

What's really astonishing
about this one,

the news editor who's doing this,

they think,
"I know a way of selling this

"is, actually, we'll illustrate it
on the front cover."

So right on his front cover,

he has this
woodblock print commissioned,

which is actually showing depictions

of all the terrible events
which are described in the flood.

And that's kind of one of the things

which makes it almost kind of
revolutionary for its time.

And a lot of people
still couldn't read.

So the imagery on the front
of the pamphlet

is very, very powerful indeed.

Got people up trees
escaping the flood.

A baby in a crib. Animals drowning.

You know, the story of this flood
gets reproduced all around Europe.

That image and the prevalence of it,
it kind of...

even in the 17th century,
it basically goes viral.

The relentless surge of water
may have finally stopped,

but people's difficulties
are only just beginning.

Huge stretches of coastline
have flooded,

rivers have burst their banks,

and many miles of land
have been covered by water.

With much of the coastal lands
on the English and Welsh sides

already inundated from
heavy rainfall before the flood,

the extra body of water
has been catastrophic.

The church at the village of
Kingston Seymour in North Somerset

has a plaque placed there
not long after the flood

that tells us how high
the waters reached.

And this plaque records
that the height of the water

was five foot in the church.

The plaque states that
many persons were drowned

and much cattle and goods were lost

and how long the waters took
to subside.

The water in the church
was five-feet high,

and the greatest part
lay on the ground about ten days.

The parish register
for Almondsbury in Gloucestershire

offers more clues.

The register tells us
that there was this great flood,

and then you also see
the burials of people.

And it took quite some time,

almost a month for the last
of those burials to happen.

So clearly,
it also took quite some time

for people's bodies to be found,

for that area to be accessed.

Records barely exist
for the devastation caused

along the Welsh coast.

Names or numbers
of the dead weren't recorded.

We don't know the extent
of the loss of life in Peterstone.

But the church
has always had a problem

when the water table is really high
or there's been a lot of flooding

because they can't bury their dead
in the churchyard.

And so we think that probably
any casualties from Peterstone

would have been taken to be buried
at nearby Rumney Church.

A huge coordinated effort
would be required

to organise the clean-up operation.

The biggest problem they had
was the fact that

because the water is now
inside these flood barriers,

it takes days or weeks
for water to be able to then

kind of drain that land.

These are rich agricultural lands

that these people's ancestors have
farmed for thousands of years.

If they are to have any future here,
they must do as their ancestors did.

And also, in lots of places,

it's actually breached
the flood barriers.

So the defences have been
kind of washed away,

and they have to be rebuilt.

There is a huge undertaking
to find and bury the dead.

The clean-up and rebuilding
operations are colossal,

all in extremely tough conditions.

Landowners are expected
to contribute to a central fund

to repair or replace
the vital sea defences.

500 men alone are employed
in Somerset

to rebuild the sea wall at Burnham.

It is laborious, painstaking work.

It was a collective effort,

so people owned or tenanted land,

and they were responsible
for whichever drains

or sea walls were on their land.

In the aftermath of the 1607 flood,

they were very, very busy,
as you might imagine.

It will take many months for life
to get back to anything like normal,

but people are determined
to carry on and not be defeated.

But the story of the flood
refuses to go quietly into history.

Scientists and historians
are continuing to investigate

the unique factors that could have
caused these huge waves.

The early 17th century

sits in a period known as
the Little Ice Age.

It's a period from
the 16th and 17th centuries,

goes on to the 19th century.

Within that period,
there's different periods within it.

And this one period
between 1560 and 1630

is usually called
the Grindelwald Fluctuation.

The Grindelwald Fluctuation

is a period
within the Little Ice Age

which saw huge expansion of glaciers

in the Grindelwald area
of Switzerland.

We know that it was
a very cold period.

And we know that there were
some extreme weather

or extreme climate change
in this period.

It's not just that things
are getting cooler in this period,

but it seems like the whole
climatic system is disturbed

and mixed up.

But it wasn't just
the global climate

during that period
that caused these huge waves.

As we're coming up to the flood,
we have a new moon.

The biggest tides,
the spring tides,

occur after the new
or the full moon.

Spring tide is just the big tides
we get every two weeks

as a result of the lunar cycle.

They happen at new moon
and full moon,

and it's when the water level
in the tide cycle is at its highest.

And then you'll get an extra special
type of spring tide, as in 1607.

That happens once every
four and a half years.

It's to do with
a special planetary alignment,

and this will obviously increase
the sea height, tide height

a lot more than you would normally
have on a normal spring tide.

It was a combination of all
these factors that proved so deadly.

If it had just been the tide,
it wouldn't have caused a flood.

The only real reason why you get
these flood events

is usually when you get
a storm surge.

Storm surge is the other component
of high water levels at the coast.

And that's when
a very big depression,

a big storm system,
pushes water ahead of it.

So the high wind speeds
push water ahead of the storm,

and that raises the water levels
at the coast.

And it really does depend on timing.

With the 1607 flood,
there was a storm.

If that storm had come
an hour or two earlier

or an hour or two later,
we wouldn't have had a huge flood.

So those two factors together,
the tide and the storm surge,

are what creates
the high water levels at the coast.

And in the case of the 1607 event,

we combine a tide that's almost
at the highest level

that we ever see
in the astronomical cycle,

with a big storm surge
of one or maybe 1.2m.

But this is only the beginning

of a historical and scientific
detective story.

A team of geologists

have proposed that this event
was Britain's own tsunami.

Have they solved the mystery
of the great waves?

SAMANTHA BOND:
It is the 30th of January, 1607.

Huge waves have swept up the
Bristol Channel and Severn Estuary,

flooding lands and destroying lives.

In 2002, a team of geologists
led by Professor Simon Haslett

suggested a new possible cause -
a huge tsunami.

Tsunami are usually associated
with Asia and the Pacific,

so a tsunami hitting British shores
would have been extraordinary.

A tsunami is a wave
that is created

by a displacement
of the water column,

and that displacement can be caused
by undersea earthquakes,

which can actually shift the seabed
up and down.

It can be caused by landslides
under the sea.

Tsunami tend to be very powerful
because they contain within them

the energy that's transferred
to them by whatever caused them.

Simon and his team embarked
on a mission to gather evidence.

Previous authors talked about
sand layers occurring

in the Severn Estuary margins.

And if you know the Severn Estuary,

perhaps driven across the
Severn Bridge and things like that,

you'll know by looking down
that it's a very muddy estuary.

To see layers of sand
is quite unusual

and requires an explanation
for how they got there.

And also, a general stripping away

of the salt marshes
of the Severn Estuary,

because we think, from the previous
work that's been undertaken,

that none of the salt marshes
that currently exist

in the Severn Estuary date back

before the middle
of the 17th century.

But it's at Dunraven Bay
on the South Wales coast

that Simon found
the most convincing evidence yet.

We looked at boulder accumulation.

Boulders elsewhere have been seen
to be a good indicator,

whether they've been moved
by either storms or by tsunami,

and so by measuring them,
we can work out the forces,

the wave height that is required
to move these boulders.

The results of our boulder analysis

has shown that only a relatively
small tsunami would be capable

of moving the boulders into the
accumulations that we've identified.

So from our studies, the results
indicate that these boulders

are much more likely to be moved
by a tsunami than by a storm.

But historians have struggled
to find accounts of seismic activity

from the period big enough
to have caused such a tsunami.

But there is a third possibility -
a different type of tsunami.

A meteotsunami is an ocean wave

caused by a rapid change
in air pressure.

What happens is
we get a storm out at sea,

and the dramatic change
in air pressure

from the low pressure centre
of the storm

will alter the sea level.

On average, in the UK,

we get five to seven
meteotsunami a year.

Simon's research was a call

for experts of all disciplines
to try and solve this mystery.

When the tsunami theory
was first mooted in 2002,

it sort of sparked a bit
of a imagination with me.

And so about 15 years ago,

I sort of rose to their challenge

which they had put out
in their paper saying,

"Look, in order to test
our hypothesis,

"we need somebody to look in depth

"at the historical
and the archaeological records."

From my own research,

which has been very detailed
in a lot of different records

that people wouldn't normally
have thought about using,

I have managed to pick up
information about the storm itself.

One of the major clues
is that we know from a true report,

the first of the pamphlets,
that there was a storm,

a storm surge over in Norfolk
on the same day,

but in the evening.

Rose Hewlett is writing a PhD
at the University of Bristol

on the evidence
for the 1607 flood being a storm.

So for now, the debate continues.

The jury's out on whether the
1607 flood was caused by a tsunami

or by a storm
or by some other mechanism.

So we really do need to push ahead

and look at these other avenues
of research

so we get a better evaluation
of the competing theories.

But what worries most people,

especially those living
along this treacherous coastline,

is could something like
the 1607 flood happen again?

Events such as the 1607 flood

have happened before
and could happen again.

We've certainly had
very large storm surges.

There's so many variables,

and you've just got to have
everything lined up

to get something that's enormous.

Paul Bates is a professor
of hydrology

at the University of Bristol.

He uses all kinds of data to develop
simulations to try and predict

future extreme weather events.

What could really change
the size of floods

into the future is sea-level rise.

If we pump a lot of carbon
into the atmosphere,

we may, by the end of the century,

get 70 or 80cm of sea-level rise
along the Bristol Channel coast.

For those areas, we would have
to raise the flood defences

to achieve the same level
of protection

that we've got at the moment.

We currently protect ourselves
against events which happen

on average once every two
or three centuries.

They could theoretically
always happen,

but they have
a very low probability.

Sea level rise means
that probability gets bigger.

So that would mean that we have
to build our flood defences

at two to four metres higher
than we currently have them,

or we abandon large areas
of the coast

and decide that they are
too risky to live in.

Extreme events like the 1607 flood

show us just how lethal weather
and water can be.

And it is extreme.

This is the worst flood in the last
thousand years in the Severn.

From the pamphlets
and from the parish registers,

we get an idea of the number
of deaths.

Total immediate death toll
was between 300 and 500 people.

So still a considerable number.

And every one was a tragedy.

From the plaques in the churches

scattered across the Welsh
and English coasts...

..to the parish registers
and the chronicles

all the way to London
and the pamphlets and onward,

this huge weather event
has left its mark

on the landscape and its people
in more ways than one.

But tough landscapes
and tough weather make tough people.

Generation after generation
of farming families

stay on the land.

People were looking to reclaim land

and make the best of what they had,

er, build up their sea defences,
get on with it.

It's the trade they know.

The scale of that disaster
in 1607 appears to have been

the worst natural disaster
to hit British soil.