Canute’s Coast
By David Stanton

"I tell you naught for your comfort, Yea naught for your desire, Save that the sky grows darker yet, And the sea rises higher." - GK Chesterton



The old tale of Canute getting his feet wet while he sat on his throne on the shore, demonstrating that even omnipotent royalty could not turn back the tide, is a long-familiar one. Less well-known is that the event is sometimes placed along this stretch of coast, probably because the old capital of England was at Winchester, and the Saxon kings had a coastal residence at Southampton. Various  sites have been put forward on Southampton Water or The Solent, between the mouth of the Itchen and Lymington. Another reason may have been this part of the coast was important and famous for its double tide creating high water twice as often as elsewhere, due to it being the meeting point of the Atlantic and North Sea tides.
The ‘father of English history’ himself, the Venerable Bede, had remarked on this. He had referred to it by the Latin phrase pelagus solvendo, which has been translated as The Disuniting Sea. Pelagus is standard Latin for sea-shore, but solvendo sounds disturbingly like the origin of our word ‘solvent’ and raises the possibility it really should be translated as ‘The Dissolving Shore’. This would be an apt description of the coast here, where mud-flats abound in shallows that were once dry land and the cliffs crumble away into the sea from tidal erosion. (The disappearance of the original clifftop manor house at Highcliffe due to erosion has already covered in a previous article.) The dimensions Bede gives in the same work (De Rerum Natura) for the Isle Of Wight  - 30 miles wide, imply that since the 8th century half of it has been eaten away by erosion (today it is closer to 20). Hengistbury Head was also much larger than its present size. Concerns about coastal erosion have been expressed locally here since the 19th century, when the removal of ironstone boulders led to its losing half its area from erosion. Today, flooding hazards are not just a matter of local concern, but a national preoccupation.
What has impressed on the public mind the danger from flooding has been not only the increasing domestic floods of the past few years, but a pair of overseas disasters. One was the Boxing Day seaquake-driven tsunami in the Pacific that killed 300,000, and the other was the Hurricane Katrina disaster that overwhelmed the New Orleans levées. The media coverage of these dramatised the present danger from the encroaching sea in two respects. First was the demonstration of the sheer power of the sea itself, with consequences seen night after night on television. Second was the inadequate response of officialdom. Here, that led to Richard Lord Attenborough (who lost relatives in the tsunami) raising the matter in the House of Lords of disinterested golf-playing officials. In the Katrina disaster, the ongoing situation became a national scandal in the USA, even prompting a conspiracy theory that the neglect - both before and after - was deliberate, a form of planned slum clearance to make way for a more upmarket metropolis.
In fact, in a ‘top ten disasters’ list compiled a year after the Asian tsunami by Professor Bill McGuire of the Benfield Greig Hazard Research Centre at the University Of London, author of A Guide to the End of the World: Everything You Never Wanted to Know, it was flood-related scenarios of one type or another that dominated – tsunami, hurricane, failure of flood defences, sea-level rise, etc.

It Can’t Happen Here?
While flooding is as English as rain, there was until recently, a tangible it-can’t-happen-here assumption about such violent weather events as hurricanes -- that (to quote My Fair Lady), in Hertford, Hereford and Hampshire hurricanes hardly ever happen. But the hurricanes of October 1987 (19 UK dead) and January 1990 (143 dead across Europe, 47 in UK), dented that certainty. Throughout the 1990s, there were other storms almost on the same scale, and other ‘freak’ un-English weather events such as tornadoes manifested themselves. For example, in July 1998, a "freak" tornado wrecked the Sussex coastal town where astronomer Sir Patrick Moore lives, in an estimated 30 seconds. In the 1990s UK climatologists began to suggest the climate was becoming increasingly unstable, and English weather became less of a joking matter.
It was just a lucky circumstance that storms such as those of 1987 or 1990 were not accompanied by a major storm surge in from the sea -- although people were swept off coastal promenades, rain caused inland floods of up to 8 feet, and ships were swept ashore (plus in 1987, one luckless baleen whale). But the media began flagging up historical precedents countering any dismissive it-can’t-happen-here complacency. BBC-TV weatherman Michael Fish spent the rest of his career trying to explain away his bland on-air dismissal of a report of the impending 1987 hurricane. The irony was that he was quite right, since the overseas report he dismissed referred to a different hurricane than the one that a few hours later blew down millions of trees across Southern England.
In 2003, 50th-anniversary TV and radio documentaries were made about the North Sea storm surge which one night in 1953 breached the sea defences in England and Holland at over 1200 places along 1,000 miles of coast, drowning 1,932 in England and Holland. Vying for the title of worst UK peacetime disaster is a historic British tsunami, the subject of ‘The Killer Wave Of 1607’, a 2005 BBC2 Timewatch documentary which was postponed and re-edited after the Asian tsunami due to its sudden topicality. It documented how, out of a clear blue sky on 30th January 1607, nearly 600 km of the Devon, Somerset and Welsh coast was inundated by a wave of up to 7.5m (25ft). The ‘largest and most destructive flood in British history’ , it may have been caused by a tsunami deriving from an undersea quake, the wave reaching up to 14 miles inland (to the foot of Glastonbury Tor), leaving a temporary inland sea of over 200 square miles for ten days, and drowning around 2,000. For the benefit of sceptics, the academic study the documentary was based on pointed out a 1755 seaquake off Portugal had sent out a 15m (49ft) high tsunami that killed nearly 50,000. There has also been a claim a tsunami hit Dorset in 1868 – luckily the relatively deserted stretch of shore west of Portland.
Tsunamis can also be caused by volcanic eruptions on land where these are accompanied by quakes or cause major landslides into the sea. In 2000, Dr Simon Day of University College’s Benfield Greig Hazard Research Centre raised a scenario (covered in a BBC2 Horizon programme, 12-10-00] which got belated headline coverage after the Asian tsunami. This is that one of the periodic eruptions of Cumbre Vieja volcano on La Palma in the Canary Islands could cause a loose 12-mile-long slab of rock the size of the Isle of Man and weighing a  trillion tons to slide into the sea, creating a dome of water a mile high and generating a series of 500mph waves that would reach the south coast. The Government's chief scientific adviser Professor Sir David King said it was likely "We would have a six-hour warning before a wave of around thirty feet in height hit us." (Independent On Sunday, 2-1-05), and the head of tsunami research at Southampton Oceanography Centre warned that there was a need for better advance warning, especially during the tourist season when the beaches would be crowded.
Another BBC2 documentary covered the giant ‘freak’ waves which sailors had long reported as coming out of nowhere (the ‘Poseidon Adventure’ scenario), but which science had dismissed as unlikely. In mid-2005, science finally accepted sailors’ tales of what they nicknamed the ‘ninth wave’, a phenomenon which could explain why around ten modern ‘super-carrier’ ships disappear every year. When two Atlantic cruise ships, the Bremen and Caledonian Star, had their bridge windows smashed by 98ft waves, the European Space Agency assigned two satellites to do a  three-week sample photo-survey for the EU’s MaxWave Project, which showed more than ten 82 ft-plus waves, indicating so-called ‘rogue’ waves not only existed but were a regularly recurring event.
Besides tsunamis, there are precedents such as the 1953 storm demonstrating that ‘ordinary’ winter gales along the Channel and south coast can also create waves that will ‘overtop’ low-lying coastal areas. Locally, Bill Hoodless’s 2005 study Hengistbury Head: The Whole Story  records some eight occasions since 1879 when waves have ‘overtopped’ the Sandbank, e.g. in 1916 (when the harbour tearoom boat was wrecked) and 1935, when 100 yards of the Mudeford sandbank was overtopped and some 60 huts were swept away (at Sandbanks in Poole, another 300 beach-huts were destroyed).
Generally, the loss of life and economic damage was higher in earlier storms, when sea defences were less sophisticated - over 100,000 drowned in low-lying areas of Holland and England in 1099 while The Great Storm of 1287 drowned 50,000, wrecked England’s Cinque Ports, and changed the coastline. The ‘great storm’ of November 1703, documented in Daniel Defoe’s 1704 collection of eye-witness accounts, The Storm, destroyed almost the entire British Navy as over a thousand ships lay anchored in south-coast harbours, killing 8,000 sailors. (It also destroyed much of the New Forest, ruining 4,000 oaks the Navy needed to rebuild).
In January 2005, the Government’s chief scientific adviser Sir David King revealed the government had in autumn 2004 conducted a top-secret readiness exercise, Operation Triton, based on the fact storm “surges are increasing as global warming takes hold.” (Independent on Sunday 2-1-05). This exercise predicated a storm driving a 9-foot wave onshore, breaching sea defences as far west as Exmouth, driving the sea up to six miles inland.
A sea storm is not the only way a coastal settlement can be devastated by flooding. The more traditional English type of flood of course is due to sudden heavy rains causing rivers to overflow their banks, because the ground cannot absorb the moisture quickly enough, flooding low-lying areas. (And once the ground becomes saturated up to surface level, the water table rises, and the result can be another type of flood – the aquifer flood, where floodwater simply wells up out of the ground.) Such ‘flash floods’ can be a disaster if the topography creates a bottleneck, as with the August 2004 Boscastle flood where a ten-foot high torrent of rain-water swept through the tiny port carrying cars out to sea. This had a more disastrous precedent in the August 1952 flood in the nearby resort of Lynmouth when after a wet summer which saturated the Exmoor hills, 90 million tons of mud and rock hurtled through the town, leaving 31 dead. Locally, recent instances of heavy rains occurred in April 1998, October 2000, and January 2003 (when the rain froze, creating an ‘ice storm’).
Coastal areas with rivers at their backs or running through them are doubly at risk for the flood could come from either direction, making the construction of defences difficult. Mudeford Sandbank for instance has had defences built on its seaward side (rock groynes), but on the harbour side there are none. Yet one danger here is also the ‘high seas meets high tide’ scenario – where rain-swollen river water, on reaching the sea, is forced back by the incoming tide of a high sea. Riverine flooding is now such common hazard that some insurers are beginning to refuse cover for homes built on nearby low-lying areas, despite the fact this may affect 10% of the population. A 2004 report called Future Flooding, compiled by 60 experts for The Office of Science and Technology, under chief scientific adviser Professor Sir David King, and described as the most comprehensive ever undertaken into flooding risks in the UK, warned that along some areas of the south coast of the UK, major flood events that used to occur once in 100 years, could soon occur every three years.



The Tipping Point
Of the ‘Top 10 disasters’ on our list, six are flood-related scenarios. As well ‘South coast tsunami’, ‘Major Thames Valley windstorm’ and ‘Climate-perturbing volcanic eruption’, there is also ‘South east flood defence failure’. This last might seem a London-specific disaster, related to the prediction the Thames Barrier will, by 2030, be inadequate to stop surge tides. It was built as part of a network of sea defences consisting of 257 floodgates and smaller ‘barrages’ and 200 miles of sea wall to counter another 1953-style flood. This had not reached as far as London, but the capital had been flooded before. Pepys’s Diary of the 1660s describes Westminster under 6 feet of water, and a tidal surge in 1928 had drowned 14.
However the reason for the Thames Barrier’s predicted failure also affects the south coast westward of Britain’s geological ‘axis’, which runs from Yorkshire down to Devon. The geological phenomena known as isostatic uplift, whereby land once weighed down by glacial ice slowly springs back up over the eons, means the north and west coasts are rising (so that Harlech Castle’s watergate is now a half-mile inland), and the south-east is tilting downward into the sea. London is now fifteen feet lower than it was in Roman times, so that the tide surges 19 miles farther upstream. And locally, Roman port remains found in Poole Harbour show that the water-level was 2.5 meters or 8 feet lower then.
There is a recently recognised theory of history known as ‘The Tipping Point’ which explains how significant events may be the product of a combination of easily overlooked background circumstances. It is a refinement of Chaos Theory, said to have been invented by a weather forecaster who was curious why predictions so often failed, and found that small factors could have a disproportionate impact, so that the whole effect was far greater than the sum of its parts. For example the 1953 flood is said to have been the result of ‘…the chance coming-together of four factors at precisely the wrong moment: a strong north-westerly gale; a very deep area of low pressure; a big spring tide; and the topography of the North Sea, which gets narrower and shallower towards the south. The result: the storm surge, a tremendous piling up of water in the North Sea's southern end, which produced a sea level eight or nine feet higher than the highest normal tides.’ The theory explains events as the buildup of circumstances till they reach the proverbial tipping point …. just as an iceberg will suddenly split apart or tip over when its core temperature reaches a certain melting point. This is an apt example, for melting ice is a factor in the remaining two flood-related disasters on our list.
The first is general sea-level rise, attributed to global warming melting the Arctic icecap. This is predicted to be just under three feet (90cm) over the next 75 years according to a National Trust report. Studies which factor in a similar melting of the Antarctic icecap (as it begins "calving" giant icebergs) suggest a more dramatic rise. Computer models of rising temperatures programmed with long-term records indicate, that if Antarctica continues to melt and ‘crumble into the sea’, sea levels will rise up to 20ft (6m) this century, drowning cities such as London.

The Sea Change
Number One in our top-ten disasters list however is ‘Gulf stream collapse’. The Gulf Stream’s large-scale circulation of water brings warm water from the Caribbean north past Britain, ameliorating the climate.  The water then sinks and drifts back south to be warmed up and re-circulated. The discovery the circulation was weakening followed on studies of the ocean-current phenomenon in the Pacific known as the ‘El Nino’ Southern Oscillation, which was first identified at Xmas 1982, and has been displaying a major environmental impact every few years since. There, the shifting of an oceanic cold currents has resulted in climate destabilization around the ocean rim. In places this caused a drier climate generating uncontrollable bush fires in places such as Australia, Indonesia, and Borneo. At the same time, the west coast of America has been hit by unprecedented rains, driven by storms so strong they altered parts of the coastline. The disastrous 1997 ice storm in the northeastern US which caused $2 billion of damage was attributed to weather disruptions caused by El Nino. It is also now blamed for the unexpectedly severe weather which killed Captain Scott in the Antarctic in March 1912.
That a similar oceanic ‘oscillation’ was happening in the Atlantic was documented by a team from The National Oceanography Centre in Southampton. In 2004, aboard the research vessel Discovery, they measured the undersea temperature and salinity around the Bahamas near the Gulf Stream’s southern end, and found that compared to similar measurements made from 1957 onward, the deep-ocean return flow had fallen off around 30%.
The ‘ North Atlantic Oscillation’ theory came to public notice when it was exploited for its melodramatic possibilities in Hollywood’s 2004 big-budget The Day After Tomorrow. Although this compressed the time-scale and wildly exaggerated its effects, it is based on a scientifically-accepted theory,  covered less dramatically in “The Iceberg Cometh,” a Xmas 1998 Channel 4 documentary, and later a 2004 BBC2 Horizon documentary which opened with a Dover ferry sailing past icebergs. Strictly speaking, the problem concerns the return undersea flow of water, ‘the Atlantic conveyor belt’ at the Stream’s northernmost section, known as the North Atlantic Drift.
The weakening is thought to result of large-scale melting of the Greenland icecap. A report given at the 2006 American Association for the Advancement of Science conference said that the amount of Greenland meltwater has almost doubled in five years. The scientific concern is that the heavier glacial meltwater is sinking and diluting the ‘conveyor belt’ current. If the circulation fails due to lack of undersea return flow, it would leave Britain with a ‘Russian’ climate more normal for its latitude. (Normal winters would become like the ‘freak’ winters of 1947 and 1963, with of course the flooding that always follows sudden melting of snowdrifts.) At the same time, the melting glaciers would mean a rise in sea level, as well as a stormier climate. For although global warming was initially depicted in the press as a change to a dry Mediterranean climate akin to the summer of 1976, there is now a growing use of the term ‘British monsoon season’, where long-term drought is punctuated by an early-summer period of heavy rain – which also brings us back to the ‘flash flood’ scenario. While industrial pollution is now recognised by science as the catalyst in climate change (the ‘greenhouse effect’), there is also a theory that much longer-term natural cycles are also involved.
There is a saying that those who ignore the past are condemned to repeat it, and lately two academic disciplines have emerged to study the history of climate and thereby detect any long-term patterns. One is Phenology, defined as “the study of recurring natural phenomena, especially in relation to climate”, and the other is Paleoclimatology, the study of ancient climate and climate evolution. On the premise our future is mirrored in the past, studies produced by these two disciplines are regularly featured in the newspapers, and the subject is also timely enough for what previously would have been academic textbooks to appear as mainstream paperbacks. An example of phenology is the work of  the British-born yachtsman-turned-anthropologist Brian Fagan. His The Long Summer: How Climate Changed Civilization looks at the rise and fall of civilisations over the past 15,000 years, due to climate changes such as the shifting of the monsoon belt. An example of paleoclimatology is the work of Professor Of Geophysics Stefano Tinti at Bologna university, who traced evidence of 232 tsunamis that have hit Europe since the Stone Age, commenting “Many of them were so powerful that they altered the course of civilisation.”  The theories themselves differ as to the underlying cause of such cycles, but most pertinent to the projected failure of the Gulf Stream is the theory that ocean circulation is based on a cycle of oscillating deep-sea currents.



Titanic Weather We're Having Lately?
The theory was first publicised in a popular-science classic by US biologist Rachel Carson, The Sea Around Us, which pioneered public awareness of marine issues after becoming a year-long bestseller and winning the 1952 National Book Award. It was proposed by Swedish marine scientist Otto Petterson, who published his theory scientifically in 1912, the year of the Titanic disaster. Over many years, Petterson's test instruments had revealed a fluctuation in undersea Atlantic tides, which at peak strength reach into the Arctic Sea and disturb the layer of colder fresh water under the ice (Arctic freezing desalinates sea-water). This is similar to the El Nino phenomenon, where warmer water periodically displaces the normally cold currents in the Pacific. Surface tides being lunar, Petterson argued that secondary alignments between Earth, Moon, and Sun increased the gravitational pull on the ocean, the effect peaking every 9th, 18th, and 36th year. The effect also increases the size of the circumpolar vortex of Arctic weather fronts, displacing the warm Gulf Stream, and creating weather chaos. According to the Petterson theory, warmer Atlantic seawater rolling in underneath the Arctic ice, disperses icebergs every 9th, 18th, and 36th year. This is where the Titanic comes in, encountering an iceberg farther south than expected in the unusually warm currents of 1912. (Titanic was at the same latitude as northern Spain when she sank.)
Petterson argued from historical evidence there is a overall oceanic cycle of  18 centuries. He argued the earliest peak of this cycle for which we have historical evidence takes us back to the warm period of the 13th Century BC. Prehistorians refer to this time as the Age of Migrations, when drought forced Mediterranean nations to migrate, with many resulting wars, and hillforts spread across Europe. It is the time of the Iliad and Odyssey, just before the Mycenean collapse in the wetter Greek "Dark Ages" when the once-fertile hills of Greece were ruined by rains washing the topsoil into the sea, and in Europe, Celtic lake villages were abandoned as freshwater levels rose.
Next came an era of climate downturn inspiring the long winter of Nordic myth, of Ragnarok and Gotterdammerung, when the old golden age ended, ending centuries later as northern tribes pushed south to attack Rome itself. This was the Late Iron Age period, which climate historians recognize from tree-rings and the growth of blanket bogs as a colder wetter phase, and the Roman geographer Strabo said floods had caused more deaths in northern Europe than wars. There is extant an Early Mediaeval Frisian account, a dynastic family history which says it was copied out to save it from the terrible floods -- the floods of the Early Middle Ages which would kill over 100,000 people in Holland and England. It reports the whole coast was wrecked in 306 BC by drifting ice and storm-floods, and that this catastrophe was preceded by an even worse one 18 centuries before. Climatologists refer to this, around 2200 BC, when Stonehenge was abandoned incomplete, as the changeover from the Atlantic Phase to the Sub-Boreal phase. This was also when many early eastern civilisations mysteriously failed or disappeared – now attributed by writers like Brian Fagan to the shifting of the monsoon belt southward.



The last warm peak in the 18-century cycle, according to the Petterson theory, began in the Roman era, when Britain's natives lived largely on corn and there were vineyards in southern England, ending around the 6th Century AD, when the Saxons were driven from their homelands in low-lying German coastal areas, possibly by rising seas. The climate warm-up lasted 9 centuries, ending in the Early Middle Ages. In the early 13th Century, the Vikings' "Vinland" farm colonies in Greenland and North America, established in the 980s, were being abandoned. In Britain came the five centuries climatologists call the Little Ice Age, when glass was first fitted to windows, the idyllic Greenwood of Robin Hood ballads became a nostalgic memory and Shakespeare in A Midsummer Night's Dream made fun of wet English summers. According to America’s famous Woods Hole Oceanographic Institute, this cold period of 1350-1900 was due to Gulf Stream weakening. By the late 17th century, it had turned so cold that south coast ports were closed as waterways like Southampton Water froze over. The Great Frost of 1740-1, with its subsequent flooding, devastated England and killed nearly half the population of Ireland -- more than the infamous potato famine a century later.
Temperatures began to warm in the 19th century. Mr Pickwick's ice-skating adventure, around 1836, would represent one of the last regular occasions for this type of winter sport outdoors in England. (There were 40-foot snowdrifts in London at Christmas 1836.) The Sea Around Us refers to a dramatic Arctic warm-up beginning noticeably, in terms of immediate 9-year cycles, in 1903 and 1912, the Titanic year. Ice core samples show the ongoing break-up of the Arctic ice shelf began around 1900. In Petterson's theory, this accelerating warm-up will continue to rise till 2150 AD. Rachel Carson implies there is still something startling about the current sudden warm-up this past century. (Brian Fagan’s The Long Summer also documents a similar accelerating warm-up during the past 150 years.) The implication that global warming must have begun to accelerate in the 19th Century, when the end of the Little Ice Age coincided with the start of the Industrial Revolution, as Blake's ‘dark satanic mills’  began to spew out smoke and other pollutants on an industrial scale.
Petterson’s theory was ultimately an astronomical one (based on solar-system conjunctions), and other scientists since then have also suggested the answer lies in the stars, though based on different cosmic cycles. Astronomy professor Dr Victor Clube, author of The Cosmic Winter, argues that not only the past cycle of Ice Ages but current climate changes are the result of the earth’s orbit passing through a belt of sunlight-blocking cosmic dust from former comets every 2,500 years – a length of time equivalent to a zodiacal ‘age’ such as the Age of Aquarius.
As scientific evidence mounts up that, in future, flooding will be an inevitably more frequent occurrence – that the once-in-a-century-high-seas are now likely to occur every few years, coastal protection strategy has begun to shift. The emphasis is now on defending only what can be defended, and abandoning the rest to the sea.  At Studland Beach, landowner the National Trust has announced the 270 beach huts there will likely not last another twenty years, as there is nothing they can do to stop the beach eroding away at 3m per annum, taking the sea wall with it. At Hengistbury Head, English Nature has refused permission for further sea defences so that geology students can observe the erosion for study purposes. A local consultant in coastal geomorphology recently summarised the issue in the Echo [16-9-05] as ‘Canute versus Neptune,’ adding, ‘I know where I would place my money.’
It seems the wisdom of Canute has come home. For it was not personal megalomania that led to his chair being planted by the seashore as the tide approached. A careful reading of the original source, Henry of Huntingdon’s Historia Anglorum, indicates that the pious Canute only agreed to the demonstration to end his courtiers’ fawning flattery about his omnipotence. As the tide washed over his feet, he proclaimed, 'Let all men knew how empty and worthless is the power of kings, for there is none worthy of the name, but He whom heaven, earth and sea obey by eternal laws.’



Further Reading
Coast-erosion and related issues are discussed in detail in Bill Hoodless’s 2005 study Hengistbury Head: The Whole Story (Poole Historical Trust 2005).
Environment Agency Flood-Risk map: The Environment Agency is launching a £30m online map to tell homeowners in England and Wales for the first time what flooding risks they face [click here].