At www.sciencedaily.com/releases/2013/05/130509091118.htm … underwater investigation of the medieval town of Dunwich has recently been undertaken – funded and supported by English Heritage. The ruins of the town lie on the sea bed, off the coast of Suffolk (just south of Southwold, home of Adnam's bitter). DIDSON technology has been used to counter the very cloudy nature of the North Sea at this point. It is surprising how much of the town still remains as the town did not disappear in one event but over several centuries of successive storms and high tides. Not only that, there is evidence that threatened churches were sometimes purposely dismantled in order to salvage features for elsewhere, prior to their final flooding. The survey of the sea bed also found 6 further ruined sites on the sea bed and 74 potential archaeological sites.
Dunwich had 8 churches and was a substantial town, a major port, and it's demise occurred as severe storms became common after the end of the Medieval Warm Period, brought on by the cooler weather that eventually developed into the Little Ice Age of the 17th and 18th centuries. It is possible that global sea levels had risen as a result of the warm climate in the 11th and 12th centuries – but proof of this has not been sought. Rather, climate scientists have concentrated on debunking the actuality of a medieval warm period as it threatened the concept that modern warming was a unique event and attributable to human activity.
Nigel Pennick, in his book Lost Cities and Sunken Lands (Capall Bann:1997) devotes 10 pages to Dunwich and here we learn the town had 52 churches, chapels, religious houses and hospitals, as well as a king's palace, a mansion house, and a mint. Dunwich was an important place. It was also connected to Bury St Edmonds by an old Roman road known as the Kings Highway. It probably began life as a Roman station.
In the Saxon period (pre Conquest) Dunwich was situated on a cliff top (hence the etymology as dun = hill) and surrounded by a ditch and earthen bank, part of which survived until as late as the 18th century. Pennick also notes Dunwich was being overtaken by the sea as early as shortly after the Conquest (at the beginning of the Medieval Warm Period) as part of the town had been lost to the tides (as it is preserved). In 1328 a storm altered the configuration of the sandbanks off Dunwich and blocked the harbour mouth. New harbours were created on several occasions thereafter and each time storms devastated them. In 1464 another storm swept away more of the town. In 1608 the Kings Highway disappeared (as it approached Dunwich) and in 1677 the market place (in what remained of the town, relocated behind the old one) collapsed as the cliff gave way (presumably as a result of excessive precipitation). In 1729 the cemetery of St Peters fell into the sea and in 1740 another storm brought the town to an end altogether. It is now a village situated inland – but the butchers shop sells some nice local sourced venison.
Nearby Aldeborough has had to move inland too, on several occasions. Here you can purchase freshly caught fish on the beach front but the old town is on the sea bed, like Dunwich. In contrast, to the south, in Essex, there has been little coastal losses as storms are not so disruptive, it seems. However, the former seaport of Orwell (on the estuary of that name) and parts of Walton on the Naze, have been overcome by the sea.
HH Lamb, in Climate, History and the Modern World (Routledge:1982) blamed a downturn in climate, a cooling event, which first affected Greenland and Iceland, one population disappearing and the other halving, that was manifest in other parts of Europe including the North Sea basin. In Iceland the sea ice grew and polar bears became common visitors. In the North Sea there was an increase in wind storms and sea floods from the 13th century onwards. The Dutch and German coastal regions were particularly affected, with great loss of life recorded (from sea inroads) and the numbers involved were in there hundreds of thousands. Half the agricultural land in Schleswig was swallowed by the sea and the Zuyder Zee in Holland came into being (drained in later centuries), and the island of Heligoland shrank from 60km across to just 25km across, as early as 1300. In England the port of Ravensburgh, near Hull, and DFunwich, were lost – in several stages. Huge losses of life during sea storms are recorded in the 15th and 16th centuries. In 1570 alone 400,000 people perished. It seems that warm periods = a lull in storms and windiness, and cool weather, the opposite. Bring on the global warming – I wish.
In Basil Cracknell's book, Outrageous Waves: Coastal Change in Britain through 2000 Years (Philimore Press:2005) Dunwich appears on several pages (in the index). This is a cracker of a tale and the result of a lifetime of collecting data. Cracknell says that many Roman period settlements around the coastline of Britain disappeared in an earlier cooling event, in the Late Roman and early Saxon period. They were lost to the sea. The harbour and fort at Caister, for example, fell out of use and was abandoned for several hundred years. The Roman settlement off Lowestoft was drowned and the Roman town of Dunwich was also overwhelmed and many Roman remains have actually been retrieved from the sea bed, a mile or so offshore. Felixstowe was also a Roman town – but suffered from erosion, and again, the Roman settlement near Walton, was affected. So, it wasn't anything new. A cooling climate in the 4th and 5th centuries AD caused widespread sea floods and wind storms much like what happened in the 13th and 14th centuries, and again in the 17th and 18th centuries. The question is, was this as a result of rising sea levels or was it because, for some otherwise unknown process, the land depressed in relation to the sea?