Historic Scotland (HS) commissioned Orkney Research Centre for Archaeology (ORCA) to undertake an archaeological desk-based assessment of key marine datasets for Orkney and the Pentland Firth. This work took place between October 2011 and March 2012 as part of Project Adair, a partnership between Historic Scotland, the Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS) and Orkney and Highland Councils. Marine datasets were collated, evaluated for their potential for archaeological analysis, and interrogated to enhance and amend the existing inventories. A variety of recent and traditional datasets were used including marine geophysics, historic charts, aerial photographs and local knowledge. Large spatial gaps in data coverage were identified including west of the Pentland Firth, and in shallower waters around the coast and islands. Areas of the seabed have been surveyed at resolutions that are sufficient to detect large upstanding remains such as iron shipwrecks but insufficient to identify smaller archaeological features. Other datasets have been created at a resolution detailed enough to allow the recognition of smaller anomalies but in some cases possible processing of the data removed small anomalies.
A methodology was developed that enables information gathered from similar studies to be effectively assimilated within national and regional inventories and to support cultural heritage within new marine planning, protection systems and the management of offshore resources. In addition to this report, the project results include a database that will readily map to Canmore and Local Authority databases, as well as a shapefile with site-area polygons. As a result, the project has enhanced the historic environment record for the Orkney Waters and the Pentland Firth. A total of 569 ‘sites’ have been investigated as part of this project. Of these, 462 ‘sites’ had not previously been recorded in the HER records. Of the 107 sites, that had been previously recorded, only 12 of these did not have to have their position corrected by the project. Polygonisation of records resulted in GIS-based shapefiles identifying areas of archaeological potential in relation to wrecks; submerged prehistoric landscapes and sites; and anchorages and fishing areas.
The presence of bedforms on the geophysical data provides evidence of the local seabed conditions. This will assist management of maritime cultural heritage as it has highlighted areas of preservation potential for submerged terrestrial as well as marine sites. Where features are located in areas of high-sedimentary cover archaeological potential may be expected, particularly where sediments remain largely undisturbed. The evidence from this project suggests that it is seldom possible to discount presence of archaeological material altogether even in a high-energy area.