A British Tsunami? The Great Flood of 1607

On 30 January 1607 the Bristol Channel experienced a sudden influx of flood water, which scientists and historians believe was either a severe storm surge or may even have been the result of a tsunami.


The flooding effected several hundred miles of coast along both the Welsh and English sides of the channel, inflicting severe damage on coastal towns and cities. The water also pushed as far up the channel as Gloucester, and flooded the major urban center of Bristol.

Bristol channel

The devastation the flood caused was mind-boggling horrendous. The Bristol Channel, which was still known locally as the Severn Sea (in Welsh: Môr Hafren and in Cornish: Mor Havren) at the time, was heavily populated by communities and seaports that relied on the shipping trade and fishing in the Severn Estuary. When the wave hit there were hundreds, maybe even thousands, of lives lost to the implacable waters. If the flood had hit at night when people were sleeping, rather than in the morning, the death toll would have been even worse. As it was, entire villages were wiped out and whole families lost.

On the English side of the channel the flood waters came as far as Glastonbury Tor, which is a good 14 miles inland. The sea wall at Burnham-on-Sea was crushed by the inrushing waves, inundating the unprepared villages and farms. More than 650 square kilometers of low-lying, marshy land known as the Somerset Levels, were completely submerged when “all Brent-Marsh the Sea swelled up as hye as Bridgewater.” Approximately thirty villages in Somerset were swamped, and several, including Brean, Huntspill, Kenhouse, and Kingston Seymour, were sunk entirely beneath the floodwaters. In the Church of All Saints at Kingston Seymour, “a chiselled mark remains showing that the maximum height of the water was 7.74 metres above sea level.”

An account of the flood reported that:

“Men that were going to their labours were compelled (seeing so dreadfull an enemy approaching) to flye back to their houses, yet before they could enter, Death stood at their dores ready to receive them. In a short tyme did whole villages stand like islands … and in a more short time were those islands undiscoverable, and no where to be found.”

Devon and Cornwall also suffered tremendous flooding. In the town of Appledore, which is situated at the confluences of the Taw estuary and the River Torridge, “many houses were overthrown and sunk.” Even houses on the clifftops overlooking the river were completely destroyed when the wave hit that morning. At Barnstaple, which was three miles farther inland than Appledore, the waves were strong enough to knock down houses, killing several people, and “went clean over the Pilton bridge, and so shooke the wester wall thereof, that it was moved three or fower inches out from the cawsey and much of it ready to fall down.”

The Welsh side of the channel was hit even harder, particularly the area between Laugharne and Chepstow, although the steep geography of Wales kept the waters from going as far inland as it did in Somerset and Devon. Swansea, one of the largest Welsh cities, was almost wholly submerged, and many smaller towns and villages were deluged. Cardiff was flooded into what is now the modern city center, and it’s major church, St Mary’s, near to where St John the Baptist now stands, was demolished in the waters. St Mary Street is the only reminder of the former church.

Other seaports and villages along the South Wales Coast — Cowbridge, Barry, Ogmore, Port Talbot, Lanwit Major, and Newport — were also battered by the flooding. Some of those villages, such as Cwm Colhuw, were never rebuilt after the seawater claimed them.  “Children at school, and travelers on the road alike were involved in this general calamity” and “many were involved, before they were aware of their danger.” Tide waters rise rapidly in the Bristol Channel even in normal conditions; it “has the second largest tide in the world and tidal currents of up to 8 meters per second [26 feet a second], twice a day, every day”, so can not be overstated enough how quickly the disaster would have struck.

The floodwaters also destroyed lives and property in 26 parishes in Monmouthshire.  A witness to the flooding, William Welby, recounted in Lamentable newes out of Monmouthshire in Wales  that:

“spoiled by the greevous and lamentable furie of the waters: Matharne, Gouldenlifte, Portescuet, Nashe, Lanckstone, Bashallecke, Roggiet … So violent and swift were the outrageous waves that in less than five hours’ space most part of those countries (especially the places that lay low) were all overflown, and many hundreds of people, men, women and children, were quite devoured; nay, more, the farmers and husbandmen and shepherds might behold their goodly flocks swimming upon the waters – dead.”

In Llandaff, which is a good 4 miles inland of Cardiff city center, a Mistress Van, “a gentlewoman of good sort”, saw the the incoming waves but was taken “by the surging swell before she could reach an upper room in her house”. One of Van’s neighbors escaped with her life, but lost everything – including all her sheep – in the disaster.

There were, however, also some stories of miraculous survivals. A four year old girl was saved when her mother lifted her to a wooden beam in the house before the waters hit, and an infant was rescued from a floating cradle with the help of a cat, “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.” In Wales, “a milkmaid was rescued from drowning by ‘two lustie strong men’ who made a boat from a water trough” and valiantly paddled through the waves to save her.

Human agency also revealed itself in the best of ways. In Monmouthshire a local member of the gentry, 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”. The mayor of Bristol was also active in sending boats “to help rescue people and presumably bring in supplies of food” to the surrounding area, even though Bristol itself was profoundly damaged by the flood.

The surging waves had forced their way up the River Avon into the heart of Bristol, “being partially dammed back by the Bridge, flowed over Redcliff, St. Thomas and Temple Streets to a depth of several feet. St. Stephen’s Church and the quays were deeply flooded, and the loss of goods in cellars and warehouses was enormous.” The waters destroyed homes and bridges, and flooded the streets so that “the people of the Towne were inforced to be carried in Boates … about their busines”. The goods that had been brought in by traders from all over the country for St Paul’s Fair were also lost in the flooding.

The economy along the channel coast was left in tatters, and many “men that were rich in the morning when they rose out of their beds, were made poore before noone the same day.”

The livelihood of most people in the area was based on agricultural production and their flocks, so they were rendered destitute in minutes by the flood. The weather had been “extremely warm and very much drying [and] in the same time violets are to have flowered”, so that there was already spring sowing, even before the Candlemas (2 February) time for first planting. Sea water rushing onto the fields, especially the silt-filled and brackish water of the estuary, and sitting on the land for almost two weeks did the ground no favors and effected crop yields for several years afterward. Nearly 200 square miles of arable land was effected, and those farms had also lost considerable livestock in the flooding.

A witness lamented that:

It is a most pitiful sight to behold, what numbers of fat oxen were drowned, what flocks of sheep, what herds of kine have been lost … great ricks of fodder for cattle … floating like ships upon the waters, and dead beasts swimming thereon, now past feeding on the same.

The damage in Monmouthshire alone was estimated to have been above £100,000 – millions in today’s money.

Trading vessels were also destroyed up and down the coast. Some were driven aground, like this ship “of some three score tonne, being ready to hoist sail, and being well laden, was driven by the breach of this tempest up into a Marrish ground” and never fit to sail again. Others were dashed against the rocks, dragged over sandbars, and overturned by the waves, to the enormous loss of both life and cargo.

The influx of sea water far into the estuary also changed the ecosystem. In some ways it could have been beneficial. An influx of “high saline water mass” increases the silt and “turbidity” of the estuarine waters, and likewise increases concentrations of certain elements, such as phosphates, nitrates, and ammonia. This enriches the seabed of the estuary, and encourages marsh flora and fauna to thrive. Furthermore, there is often an increased migration of marine fishes into the estuaries after a massive tidal surge, which the local fisherman would have rejoiced to find true. On the negative side, however, the flood may also have been the reason for the “erosion down to the bedrock of two spurs of alluvial agricultural land” and the significant reduction in the salt marshes of the area.

But what caused the waters to rise on that fateful morning in 1607? Storm surge or tsunami?

For myself, I agree with the theory that it was tsunami. Although water displacement in storm surge could account for a lot of the physical evidence just as well as the tsunami theory could, the eyewitness accounts lend credence to the idea it was a tidal wave. The event was described as the waters of the sea being “driven back” before  “huge and mighty hilles of water tombling over one another in such sort as if the greatest mountains in the world had overwhelmed the low villages or marshy grounds … with the greatest violence … with such smoke as if mountains were all on fire … as if myriads of thousands of arrows had been shot forth all at one time.”

Storm surge can explain boulders being moved along the beach and deep-ocean shells in estuary strata, but fast moving, ginormous, smoking and sparkling waves following a water backflow is markedly tsunami in nature.