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The Portland Stone Wreck (Site 5011)

This unidentified vessel is known as the "Portland Stone Wreck" and is most likely the remains of a sailing barge or barge-like vessel that sank in the second half of the 19th century. Little of the vessel is visible above the seabed, however the lower sections of the hull are likely to be preserved under the cargo of Portland stone, which is stacked to a height of four metres above the seabed.
 
From the available evidence, the "Portland Stone Wreck" was a carvel built, single masted sailing vessel with a fairly flat bottom, approximately 15-16m long and 5.5m wide. The wreck lies in 7.7m of water (CD), east of Selsey Bill in an area called "The Park".
Multibeam sonar image in 3DIn August 2002 Wessex Archaeology surveyed the site using a number of geophysical methods, including sidescan sonar, magnetometer and multibeam sonar. Several dive assessments were also carried out on the site, recording the visible remains of the wreck and noting their condition.
 
In June 2003, the site was revisited for further geophysical surveying, which included multibeam sonar, sub-bottom profiler and magnetometer. There was also ten dives to the site during the fieldwork, and involved completing a plan of the wreck site using offset and triangulation measurements, sketches and dimensions of vessel features together with underwater photography and video footage (which can be viewed by clicking the red spots on the multibeam image here).
 
Comparison of the geophysical and dive data from both years showed that the site was not deteriorating markedly and that no major changes were evident.
 
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Tal-Y-Bont

The true name of the Tal-Y-Bont wreck is unknown, but it was probably a 700-ton Genoese merchant ship lost in 1709 while carrying a cargo that included carrara marble blocks and paper. The wreck takes its name from the Tal-Y-Bont beach area in Cardigan Bay where it was found in 1978 by a group of local divers, later known as the "Cae Nest Group".
 
As well as a large mound of marble blocks, the site is made up of 26 iron guns, including 25 muzzle loading guns of various sizes and a probable breech loading iron swivel gun.

Marble blocks on the Tal-Y-Bont wreck site

The site was designated as a protected historic wreck site in 1979. Cadw now administers the wreck and the site licensee, monitors the site.

Wessex Archaeology's Diving Investigations

Wessex Archaeology was asked by Cadw to investigate the wreck as a "designated site assessment" as part of our work under the Protection of Wrecks Act (1973) in 2004.
 
Wessex Archaeology divers made a detailed photographic survey of the wreck site, prepared a georeferenced plan of the main exposed archaeological features of the site and made detailed measurements of the features on the site.
An anchor on the Tal-Y-Bont wreck siteWessex Archaeology obtained a large amount of photographic data of the wreck site and produced a georeferenced site plan that can now be used to monitor the condition of the site.
 
Based on existing knowledge of the wreck site, the exact circumstances of its loss cannot be established with any confidence based on the present remains. The vessel certainly ran aground in the bay, but it is not clear whether this was an accident caused by the crews' unfamiliarity with this coastline or done deliberately to prevent an already damaged vessel sinking in deeper open water.
 
A copy of the full report of Wessex Archaeology's investigations can be downloaded as a PDF: Tal-Y-Bont, Designated Site Assessment, Full report.
 
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Unknown wreck off Hastings (Site 5007)

Sidescan Sonar - metal vessel 2This site contains the remains of an unidentified and very broken up vessel, lying in two sections. The identification of the boiler and the construction method of the riveted plate implies that the wreck was built pre-World War II, and probably sank either during the war or shortly after.
 
The wreck is situated SE of Hastings, East Sussex and lies at a depth of 16m. The dimensions of the vessel are 85 metres in length and 15 metres in width.
 
In August 2002 the wreck site was surveyed using sidescan sonar and magnetometer. The magnetometer data indicates that the vessel was made of a ferrous metal. When the site was dived a month later, it became apparent that the vessel had been disturbed after it sank. The UKHO (United Kingdom Hydrographic Office) report for the wreck site noted that the vessel had been swept and dispersed in 1956, confirming the dive results.
 
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SS Mendi report online

The last post on the wreck of the ss Mendi described the recent assessment of geophysical data for the site carried out by Wessex Archaeology.
 
We are please to announce that the ss Mendi geophysical assessment and desk based assessment project reports are now available.

LiDAR in Archaeology

LiDAR (Light Detection and Ranging) data is produced by attaching a laser-scanner to an aircraft. A cloud of measurement points across the landscape is produced as the laser-beam is fired at the ground and measured when it is reflected back to the aircraft.

Depending on how high the aircraft flies and how the raw data is processed, this typically results in a dataset of points spaced between 25cm and 2m apart, with a vertical tolerance of up to 20cm.

The highly detailed terrain models which can be produced from this data are incredibly useful for identifying archaeological features, even those which can barely be seen with the naked eye. In addition to the spatial component of the data, the intensity of the reflected laser beam is also recorded and this can be used to identify buried features where they cause changes in the vegetation cover or soil moisture content and hence the amount of absorption and reflectance of the laser beam.

Increasingly, this data is being used in our work. Wessex Archaeology has developed an effective methodology for the processing and analysis of such datasets. The biggest problem with these datasets is the volume of data, especially for large study areas. We have overcome this using the latest features in ArcGIS9, using appropriate data storage formats and processing routines capable of handling enormous datasets.

The latest project to make use of this approach to LiDAR data involved the processing of 19 strips of LiDAR data containing 133.5 million data points and covering an area of around 40 square km. This was processed to produce two multi-resolution Triangular Irregular Network (TIN) surfaces suitable for analysis, one for the elevation component and one for the intensity component.

These were used to produce derived analytical products such as hillshaded raster images and slope surfaces at the resolution of the source data (c.1m) ready for interpretation and digitisation of key features.

The advantage of processing this volume of data in one go is twofold. Firstly, any edge effects at the edges of the strips of data are minimised. Secondly, the amount of manual intervention is significantly reduced; had the data been processed in individual strips, it would have been necessary to undertake an additional stage of processing to clip and mosaic the datasets.

Much of this LiDAR data is being produced by the Environment Agency who are surveying areas of the country as part of their Flood Plain mapping programme. There is more information on LiDAR including how to obtain data and coverage maps on the Environment Agency website.

The image below shows an overview of the processed LiDAR data.

Example plot of LiDAR dataExample plot of LiDAR data

B-17 bomber off Newhaven (Site 5002)

B-17 bomber engine This site is the wreck of a World War II bomber, identified by its engines as a B-17 Flying Fortress.
 
It lies in 16m of water, 2.4nm SSW of Newhaven, East Sussex.
 
As an aircraft lost in military service, the site is protected under the Protection of Military Remains Act 1986. Reports from a dive investigation in 1975 indicate that the tail section and wings were visible on the site and therefore it is assumed that the plane was ditched and sank intact, rather than crashed. The Royal Navy removed the wings later that year after a diver died on the site; a tragedy believed to have been caused by the hazardous nature of the site.
 
In 2002 a geophysical and diving assessment of the site was completed by Wessex Archaeology to confirm the aircraft type and establish the remaining extent of the site. The geophysical information consisted of sidescan sonar and magnetometer data. The site was dived twice, in September 2002, to ground truth the sidescan anomalies. This survey observed that only three engines and some scattered debris remained at the wreck site, most of which are largely buried.
 
In June 2003, the site was surveyed again using magnetometer, sub-bottom profiler and multibeam sonar. Later that year, further diving fieldwork was carried out on the site which mainly comprised visual recording (photographs, video, site plan, feature dimensions) and some light cleaning of one of the engines. Underwater photos and video can be viewed by clicking the red spots on the multibeam image.
 
A comparison of the survey results concluded that the site had not changed greatly over the year and was therefore in a generally stable condition. Further information about B-17 bombers is available.
 
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Talis (Site 5009)

Wreck 5009 - TalisA combination of documentary research and geophysical data have identified this shipwreck as that of the mid 19th century Swedish steamer Talis. The vessel sank with its cargo of coal after a collision with the ss Roman. In dive guides the wreck is usually called the "1906 wreck" after the year it sank and was later rediscovered.
 
The wreck site is situated 5.56nm SE of Beachy Head in East Sussex, just south of the Royal Sovereign Shoals, in 15.2m of water (CD). The dimensions of the wreck are approximately 65m x 12m.
 
In August 2002 Wessex Archaeology surveyed the site using sidescan sonar and magnetometer. The sidescan data showed that the wreck was lying on an even keel and was largely buried. The amidship section of the vessel was broken up, which may be due to a salvage operation. The site was not dived during the 2002 fieldwork season due to adverse weather conditions.
Talis - anchorsIn June 2003 WA carried out further geophysical investigation of the site using multibeam sonar, and this corresponded with the previous year’s results. No dive survey was carried out in 2003 due to time constraints and adverse weather.
 
View geophysical images from both years' fieldwork, together with more information about the Talis and a link to find out the vessel specifications.
 
In the summer of 2005, the site was subject to both ROV (remotely operated vehicle) and diver survey. Examples of the video footage together with underwater photos, a site plan and information regarding the construction, vessel type, fittings and machinery of the Talis can all be viewed here.
 
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ss Mendi Geophysical Assessment

Multibeam bathymetry of the Mendi

Wessex Archaeology has just processed and interpreted sidescan and multibeam data from the wreck of the troopship Mendi, which sank with the loss of 649 lives after a collision off the Isle of Wight on 21 February 1917. The project was jointly funded by the South African Heritage Resources Agency (SAHRA) and English Heritage. Geophysical Survey of the Mendi During the summer of 2007 a Regional Environmental Characterisation (REC) survey was conducted along the south coast of the United Kingdom as part of the Department of the Environment, Food and Rural Affairs' (DEFRA) Marine Environment Protection Fund (MEPF) programme of regional seabed mapping. One of the planned survey lines was to pass within a mile or two of the Mendi, and at the request of Wessex Archaeology and English Heritage the REC Steering Group agreed to an adjustment of the line to allow the collection of data over the site of the wreck. What the Data Shows The geophysical data shows the wreck oriented approximately east to west - with the bow in the west and the stern in the east. The hull appears fairly coherent, but with a chaotic internal structure and some outlying deris.

Sidescan sonar image of the Mendi

Most of the collapsed wreckage from the superstructure seems to be concentrated within the hull. This confirms diver descriptions which indicate that with the exception of the bow and stern, the wreck has collapsed in many areas. Within the general collapse, the bow and stern remain relatively intact, as does the amidships section where the boilers and engine are clearly visible in the data. The bow appears to have broken away from the rest of the wreck and a large amount of scattered debris is present in this area. This may be the mark of the fatal damage suffered when the Mendi was rammed by the Darro. The break is in the area where survivors' accounts describe the bow of the Darro cutting deeply into the Mendi's hull - to within a couple of feet of her midline. What the geophysical data also appears to show is that when compared to diver reports about the condition of the wreck, the bow and stern have seen a marked deterioration in last 3-5 years, and this may be indicative of a more general, rapid degradation of the wreck as a whole. Previous Work The geophysical assessment builds on previous work conducted by Wessex Archaeology in 2007. To coincide with the 90th anniversary year of the sinking of the Mendi, funding was provided by English Heritage to undertake a desk-based appraisal of the wreck and its story. This appraisal drew together a huge amount of information about the events surrounding the loss of the ship. It gathered, for the first time, available information about the wreck itself, and allowed us to start creating a picture of the wreck site - its layout, condition and state of preservation. Perhaps most importantly, the desk-based work showed that the wreck of the Mendi is an important physical focus for investigating a little known and largely forgotten aspect of World War I history - the story of the British and Foreign Labour Corps. Of the men who died when the Mendi sank, most were non-combatant black South African labourers, en route to France to support British operations on the Western Front. Future Surveys The recent geophysical assessment has identified a range of target areas for investigation during a Remotely Operated Vehicle (ROV) survey that Wessex Archaeology hopes to carry out on the wreck in the near future. We would like to gather better evidence of the condition and relative stability of the wreck, the possible impacts of human intervention on the site since its discovery, and the information relevant to its future survival. We're also interested in a non-intrusive investigation of the artefacts that survive on the wreck which speak for the presence of more than 800 South African servicemen on the Mendi when she sank.

Artefacts from the Sea: new pages online

Mesolithic Tranchet Axe from SolentThe recent discovery of Palaeolithic handaxes in the North Sea has underlined the link between aggregate dredging and archaeology. To help let aggregate companies know where prehistoric remains might be found, and to target new surveys, Wessex Archaeology has been looking again at old records of artefacts found at sea and on the coast. Often, little of the information about such discoveries was recorded at the time because people were not so interested in marine archaeology. Today, this information can be very valuable, once it has been tidied up in a way that can be easily accessed through computerised records. Wessex Archaeology’s ALSF project Artefacts from the Sea concentrated on making information about old discoveries more easily available through the National Monuments Record (the NMR, maintained by English Heritage) and through Historic Environment Records (HERs, maintained by local authorities).
 
Our project looked at two areas: the Yorkshire coast between the Humber and the Tees, and the Solent in southern England. Records of hundreds of discoveries were added or improved in each area. As well as re-examining finds made at the coast, the project also catalogued a very important collection of prehistoric finds held by fisherman Michael White. Almost 300 finds from 59 different places in the Solent were catalogued, ranging from the Lower Palaeolithic to the Bronze Age. The Artefacts from the Sea project successfully demonstrated the value of re-examining previous discoveries as a cost-effective way of improving our knowledge of the likely presence of prehistoric material offshore. Our new pages detailing the methods and results of the project can be found here.
 

Seabed Prehistory: reports online

Seabed Prehistory: Vol I The reports from Wessex Archaeology's ALSF Seabed Prehistory Project have been made available online via Scribd, where they can be viewed or downloaded as PDFs (you will need to create a free account and log in to download).
 
The reports set out details of marine geophysical, geoarchaeological and palaeo-environmental studies.
 
There are eight volumes covering five study areas, plus an Introduction and Results and Conclusions.
 
Find out more about the Seabed Prehistory project.
 
To see the online reports, click on the links below:
 
Seabed Prehistory: Gauging the Effects of Marine Aggregate Dredging
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