October 2013
Dunwich was once one of the largest towns in England. It may have been the site of a Roman coastal fort and established itself as an important centre for Christianity. However, the majority of the former town is now in ruins beneath the sea due to ongoing cliff retreat. The underwater ruins have been called Britain’s ‘Atlantis’
In this article, we turn the clocks back to the 11th century to see how the Dunwich coastline has changed over the course of a millennium. This extended history will put coastal erosion into context. Links will be made between both the human and physical geography of the Dunwich coastline.
Hear more about Dunwich from our expert, David Sear from the University of Southampton
Over the last 1000 years, more than 300 settlements around the southern section of the North Sea have been lost to coastal recession. A large proportion of these 300 settlements lost the North Sea were small hamlets and villages. Dunwich was one of the most prosperous settlements to have suffered from coastal recession. It had a population of around 4000 at its height, with at least 800 taxable houses.
The loss of a major trading hub shows that we have not always been able to protect against coastal erosion – no matter how important the settlement. Historical sites, such as Dunwich, also provide long term records of coastal recession. Because Dunwich was of national importance, there are extensive historical records that chart the struggles and ultimate demise of the town. This provides a unique chance to analyse coastal retreat on a long-term scale.
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It is the site of a major Roman, Saxon and Medieval settlement
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Coastal retreat has been occurring for at least 1000 years
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Extensive information is available about the town’s economic and social history
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The underwater ruins have already been partially mapped by divers and geophysical surveys
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The modern settlement of Dunwich is currently at risk from coastal recession
Dunwich was an important market town with a strong economy. Prior to the 1066 Norman conquest, it was one of only four towns to receive a Royal Charter for a Market. It also received a Royal Charter for a Mint - to manufacture coins. In 1086, Dunwich was recorded as being one of the ten largest towns in England.
Dunwich’s economic growth can be traced back to the development of the marine fishing industry in the North Sea, as the town was well placed to harvest near-shore herring shoals. This was assisted by a natural harbour in the form of the sheltered River Blyth estuary that entered the sea at Dunwich. The town was therefore able to charge boats a fee for mooring.
Dunwich also established itself as an important centre of Christianity during a time in which the Church had considerably more power than it does today. This is illustrated by the fact that Dunwich was once the seat of the Bishop of East Anglia.
Archeology of Britain’s ‘Atlantis’
The underwater remains at Dunwich cover an area of around 2 km2 in diameter. There are concentrations of archaeological material within this site, which provide geographical information about the former town. For example, we know that the town once had six churches, one chapel and an internationally important harbour. Sonar devices were used to create high-resolution 3D images of the sea bed and the underwater ruins. This allowed the research to create the most detailed map of the former town yet.
Charting the coastline
A range of historical documents were used to locate the position of the coastline at Dunwich through the years. Some documents also show which buildings were present in the town. The accuracy of each of these secondary sources was critically evaluated by comparing sources with one another. The secondary sources included:
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Sea atlases and descriptive sailing directions, which referred to landmarks on the coastline
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Perspective views of the coastline, which offer a sailor’s eye sketch view of the coastline
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Historical pictures and paintings give architectural information about Dunwich’s buildings
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Maps dating back to the 16th century, which showed how the city has changed over time
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Ordnance Survey maps dating back to 1849, which shows location of cliff-tops, shorelines and buildings
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Adding up the damage
Tax returns were used to determine years in which Dunwich suffered heavy economic damage from storms and coastal erosion. Maps and surveys of the town also show buildings and infrastructure lost to the sea. The town is unique as it has a well-documented social history dating back to the 13th century, with accurate cartography back to 1587. It is important that the records date so far back since much of the town was lost as early as the 13th and 14th centuries.
Predicting the future
By analysing the rate at which the coastline and seabed are changing, predictions can be made as to the future location of the Dunwich coastline. This involves using sonar technology to analyse sediment processes in the sea. Projections have been made for 2050 and 2100.
The evolution of the coastline at Dunwich is dependent on rates of erosion, which is affected by: sediment supply and transportation, tidal flows, wave regimes, storm surges, the size of the Dunwich-Sizewell bank and sub-aerial weathering.
Erosion is ultimately dependent on an excess water energy reaching to the toe of cliff. Whether the water can rise to the toe, and therefore erode it, is dependent on how high the toe of the cliff is elevated above sea level. A large amount of sediment will increase beach elevation and therefore reduce the amount of energy that reaches the toe of the cliff.
Tides, waves and storm surges can all act to increase the amount water energy that reaches the toe of the cliff, and there speed up erosion. Cliff erosion will therefore be greatest in the absence of a beach or when there is a low beach elevation (vertical height between sea level and the toe of the cliffs)
The elevation of the underwater Dunwich-Sizewell bank can have a significant affect on the water energy that is able to reach the cliff toe. A high bank will decrease offshore water depth, reducing wave height and reducing the size and energy of waves. The Dunwich-Sizewell bank can reduce the height of large waves (over 2.2m tall) by around 0.5m.
Finally, sub-aerial weathering and mass movement can cause the cliffs to weaken and crumble. This allows coastal erosion to be even more effective and it also increases the supply of sediment.
Dunwich’s history is marked by a continual and ill-fated struggle against coastal retreat. Loss of land is recorded in the Doomsday book, which notes that over half of the town’s taxable farmland was lost to the sea between 1066 and 1086.
Major losses were also suffered as a result of massive storms in 1287 and 1328, as well as additional storms over this period. Following the storms of 1328, 375 out of 400 houses in the parishes of St Leonards, St Martins and St Bartholomew were lost to the sea.
The demise of the Dunwich can also be linked to the fact that the harbour often had to be closed for repairs. Severe storms caused damage to the harbour and meant that a great amount of effort was spent restoring and protecting it. Any closure of the harbour would have meant considerable economic losses for the town, which depended considerably on trade from incoming boats.
The major losses of infrastructure and land at Dunwich during the period 1275-1350 coincided with a period of national economic crisis. Loss of income due to harbour maintenance would have hit an already ailing Dunwich economy.
The decline of fishing in the North Sea will have accelerated the decline of the Dunwich economy. During the first three decades of the 15th century (1400-1430), the fishing fleet slumped and income from the market stalls fell by 66%.
Physical losses due to cliff retreat meant that, by 1602, the town was reduced to a quarter of its original size. Storms in 1740 flattened large areas of the remaining city, so that only All Saints church remained open. By then, Dunwich bore little resemblance to its former self.
The small village of Dunwich today bears no resemblance to the bustling medieval port it once was. However the area is rich in natural and archaeological history. The former Dunwich river estuary is now an internationally recognized freshwater marsh with important breeding populations of rare wetland birds such as the Bittern.
The village also contains archaeological heritage, including the ruins of the Grey friar’s friary church, and the hospital of the Holy Trinity. Each of these is under threat to coastal erosion and the breaching of the gravel barrier that is the reason for the formation of the marshes.
Estimates based on projecting the rates of erosion forward 50 and 100 years, suggest that some of Dunwich’sarchaeological heritage will be lost within this time. Similarly, storms and rising sea levels threaten to breach the gravel barrier and return the marshes back to saltmarshes and estuarine conditions.
The landscape we see today is a product of sequences of past processes and as such there is a strong case, in the absence of sufficiently costly infrastructure, to let future processes run their course. However, this is contentious – where will the rare habitats provided by the current marshes be replaced? What do we say to those people who currently live at Dunwich?