FINAL REPORT Title: 5883 Dunwich, Suffolk:Mapping and assessing the inundated medieval town. Author(s): David Sear (UoS), Andy Murdock (GDI), Tim LeBas (NOC), Paul Baggaley (WA),Gemma Gubbins (GDI). Derivation: 1st Draft Project Report. Origination Date: 5th October 2011 Reviser(s): Unspecified Date of last revision: 9th March 2013 Version: 1.3 Status: FINAL Summary of Changes: Final report. Includes modifications specified by reviewers on first progress report and draft final report. Circulation: Project Officer Helen Keeley Required Action: Confirmation of receipt by PO. File Name/Location: Approval: David Sear Project Executive 1 | P a g e Executive Summary Project 5883 Dunwich, Suffolk: Mapping and assessing the inundated medieval town has delivered and exceeded all of the objectives and produced all the outputs as specified in the Project Design (See Table (i)). In summary the project has: 1) Compiled and digitally captured all available maps, charts and pilot books for the section of coastline at Dunwich. These have been screened and evaluated in terms of their accuracy and information content. These were used to reconstruct the limits of the town, and to determine the position of the historic coastline at different times back to 1587. 2) Applied Coastal Change Analysis (CCA) and Bathymetric Change Analysis (BCA) to a) forecast the position of the coastline in 2050 and 2100, b) hind cast the coastline back to 1000 A.D., and c) determined the synoptic and local changes in coastal morphology around the Dunwich town site. 3) Undertaken geophysical survey of the northern harbour area of the town together with detailed survey of the existing major ruins on the seabed. This included magnetometer, Sidescan sonar, Multibeam and DIDSON acoustic imaging. Constraints at the time of survey restricted DIDSON survey to one of the two sites specified in the Project Design. 4) Collated all existing land-based archaeological data and integrated this with the CCA forecasts of cliff position to determine the heritage at risk to coastal retreat. This has identified between 6-14 sites at risk between 2012 – 2080. A list of recommended future work at the site has been compiled on this basis. 5) Collated all available marine geophysical and diver survey data and used this to identify the extent and type of marine archaeology over the town site. This data has been integrated with BCA to identify risks to marine heritage. A list of recommended future marine archaeology survey at the site has been compiled on this basis. 6) Reconstructed the topography and geography of the medieval town as the basis for defining the boundaries of the site that are expected to contain most of the archaeological heritage on land and in the marine environment. Although the boundaries are contestable, they provide a basis for any future consideration for heritage protection of the site. 7) Evaluated the use of DIDSON acoustic imaging sonar for use on the Dunwich town site. We compared both quantitative and qualitative outputs from all geophysical survey techniques. The DIDSON system provides additional valuable qualitative data on the environment and archaeology of a site, and can provide quantitative data that is statistically similar to Sidescan and Multibeam data. 2 | P a g e ACKNOWLEDGEMENTS The authors wish to thank English Heritage for their support and for funding this research and in particular; Ian Oxley, Peter Murphy, Mark Dunkley and John Etté who have consistently supported the project. A special thanks too for Helen Keeley the Project Officer for all her wisdom at crucial times. The authors wish to acknowledge the assistance of the following people who helped us obtain and understand the historical documents used within this research. First and foremost, the people of Dunwich and the Dunwich Museum Trust, who have supported this and earlier projects with great enthusiasm. Also, to Andy Rose, Duncan Coles and the LearnScuba divers. For his continued enthusiasm and help with the DIDSON we thank Mike Sawkins of McArtney AS. Brian Thynne and Emma Lefley of the National Maritime Museum offered useful insight into their collections and facilitated supply of imagery. Guy Hannaford and Matt Millard of the United Kingdom Hydrographic Office Archives provided a good deal of useful information on historical charts and pilot books available for this period. We are also grateful to Katharine Chant and Giles de Bertodano of the Dunwich Museum for information and mapping from the Downing College Library, and Dunwich Museum research collection. We want to thank the staff of Maritime Museum Rotterdam, Netherlands and Christopher Jones UKHO Tides Team for help with standardising chart Datum for bathymetric change analysis. We wish to thank Jenny Wraight (Admiralty Archive, Portsmouth) who retrieved a wealth of material including charts and sea atlases and to the Jenny Ruthven, Karen Robson, Sarah Harder, A Begley, A Pavule and A Hassan of University of Southampton Library – Rare Books Section for copies of the Coasting Pilot. We are grateful to John Gator and the Time Team for access to their geophysical data, and to Wessex Archaeology for provision of the Archaeological report for the Time Team Dunwich dig. We are also very grateful to Katherine Bryson and Lindsay Jones of the National Monuments Record, Swindon who facilitated supply of historical aerial photography used in the coastal change analysis. Finally we also wish to make a special mention to Stuart Bacon of Suffolk Underwater Studies, whose pioneering work provided the inspiration for the research in Dunwich, and who provided access to original maps of the archaeology of the site found during his many dark and cold dives. 3 | P a g e CONTENTS Acknowledgements ................................................................................................... 3 1 Aim and Objectives .......................................................................................... 10 1.1 Project Aim................................................................................................ 10 1.2 Project Objectives ..................................................................................... 10 2.0 Background .................................................................................................. 10 2.1 Context ..................................................................................................... 10 2.2 Site Selection ............................................................................................ 11 2.3 Previous Work ........................................................................................... 13 2.4 Historical background to Dunwich site ....................................................... 15 3 Methodology (Objective 4) ............................................................................... 19 4 Historical Analysis methods and data sources (Objective 1) ........................... 23 4.2 Historic maps and nautical charts – the data sources ................................ 24 4.3 Sea Atlases ............................................................................................... 26 4.4 Sailing directions ....................................................................................... 27 4.5 Perspective views ..................................................................................... 28 4.6 Historic Ordnance Survey Mapping ........................................................... 30 4.7 Historic Aerial Photography ....................................................................... 31 4.8 Historic paintings, pictures and descriptions. ............................................ 31 4.9 Changes to the City of Dunwich identified from mapping ........................... 32 5 Geophysical data collection 2012 .................................................................... 34 5.2 AIMS AND OBJECTIVES .......................................................................... 35 5.3 GEOPHYSICAL DATA – TECHNICAL SPECIFICATIONS ........................ 35 5.4 GEOPHYSICAL DATA-PROCESSING ..................................................... 38 5.5 Empirical Tidal corrections & MBES Processing ....................................... 38 5.6 Magnetometer GEOPHYSICAL DATA – ANOMALY GROUPING AND DISCRIMINATION ............................................................................................... 40 5.7 Sidescan data processing ......................................................................... 42 5.8 Diver held DIDSON surveys 2010-2012 .................................................... 45 5.9 DIDSON Processing ................................................................................. 50 6 Data Synthesis ................................................................................................ 52 6.1 MAGNETOMETRY RESULTS .................................................................. 52 6.2 Northern Survey Area ............................................................................... 52 6.3 St. Peter’s Church Survey Area ................................................................. 54 6.4 St. Nicholas’ Church Survey Area ............................................................. 54 6.5 Identification of new marine archaeology .................................................. 55 6.6 DIDSON Surveys (Objective 3). ................................................................ 66 6.7 Geophysical Survey Site scale results ....................................................... 69 6.8