Marine Life Talk at NOC
5 December 2013 –
Britain’s Atlantis – Dunwich, Suffolk – Coastal Erosion, Archaeology and Ultra-high resolution sonar imaging –
The town of Dunwich on the coast of Suffolk has nearly all been lost to coastal erosion. Once a thriving sea-port is now a historic site of marine archaeological interest. The first mention of a settlement in this area was ‘Dunmoc’ in the 7th Century. In the Doomsday book (1086) there is one church but within 150 years the population had grown to about 5000 and was considered to be the 6th largest port in England. A measure of the importance of a settlement is the number of religious buildings in the town and this peaked at 18 in 1225. However after this point the town seemed to undergo a fast decline in the following 250 years.
Coastal erosion due to storms and changing currents have moved the coastline at least 1500m further inland. Today there are less than 50 houses which could be claim to be part of the ‘extended’ Dunwich village. Most buildings at that time would have been made mainly of wood and thus would not have survived. Churches and other religious buildings however were more likely to be constructed of stone and therefore it is the remains of these that may be present underwater.
Several surveys were conducted over a 4-year period (2008-2012) using sidescan sonar imagery and multibeam bathymetry at the highest resolutions. These underwater survey techniques can get a reasonable level of understanding however the fine detail is masked due to the dark and turbid waters in the area which precludes the use of underwater photography. Therefore a diver-held DIDSON sonar system was used to target individual features previously identified. The DIDSON works at 1.8MHz and can be held by a diver like a video camera with a head-up display or mounted on a tripod.
Tim Le Bas studied geology and geophysics at Durham University and started at the Institute of Oceanographic Sciences in Wormley, Surrey, after his BSc degree. After a few years he continued his education doing a part-time PhD while continuing at IOS. As the new Southampton Oceanography Centre opened in 1995, he moved to Southampton and has now been at working at the National Oceanography Centre (and previous guises) for over 25 years. He is an expert in sonar acoustics working in the deep ocean and the comparatively very shallow coastal waters. Tim has been on over 30 cruise expeditions, and leading a few. He also teaches two courses for the University: Seafloor Surveying and Exploration, and Geographical Information Systems.
History and archaeology have always been a fascination and interest for him and this project was a wonderful opportunity to combine his professional and personal interests.
Image: All Saints Church, Dunwith – before and after 100 years of coastal erosion
Recordings of some of the previous Marine Life Talks can be found on: http://www.youtube.com/user/NOCSnews
Future Marine Life Talk at the National Oceanography Centre:
Please note: For January only, the Marine Life Talk will be held on 9 January 2014 (the second Thursday of the month), topic and speaker tbc
Free admission – these talks are open to the public
The Marine Life Talks are held on the first Thursday of the month at 7.30pm, please arrive at 7.15pm.
Arrangements for wheelchairs must be made in advance. Unless it is possible to descend via the stairs in an emergency, access to upper floors cannot be permitted as lifts are automatically immobilised when the fire alarm is activated.
The National Oceanography Centre is reached via Dock Gate 4 (between Southampton’s Town Quay and Ocean Village).