The Orkney archipelago has a rich heritage that includes the Heart of Neolithic Orkney World Heritage Site, Viking settlements, harbours supplying Hudson's Bay Company ships, and the wartime naval base of Scapa Flow. This rich history has left its mark on the seabed but accurate maps showing the location and character of surviving seabed archaeology do not exist to the same extent as for archaeology on land. ORCA Marine was commissioned by Historic Scotland to work with the Royal Commission on the Ancient and Historical Monuments of Scotland in interrogating marine data sets to enhance historic environment records of Orkney Waters and the Pentland Firth. These waters were prioritised for their history of maritime activity and to help guide planning and developments in an area highlighted by the Scottish Government for marine renewable energy.
A variety of recent and legacy datasets, including wreck databases; sonar data gathered by public sector bodies; aerial photography; seabed cores; Admiralty charts; and local knowledge, were examined for their effectiveness in discovering and interpreting marine cultural heritage cost-effectively. A methodology was developed that enabled marine cultural heritage information to be quickly assimilated within the national and regional inventories for dissemination online. Polygonisation of records resulted in GIS-based shapefiles identifying site extents, and areas of archaeological potential in relation to wrecks, submerged prehistoric landscapes, anchorages and fishing areas.
Substantial gaps in data coverage were identified and 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 geophysical datasets have been created at a resolution detailed enough to allow the recognition of smaller anomalies but in some cases processing of the data has removed small anomalies of interest to archaeologists. Intensively used marine areas often contain the most artefactual remains such as historic ports being developed to service the marine renewable industry. Zones of high wave and tidal energy favoured for renewable energy devices include navigation channels and hazards where a large number of wrecks are documented. Transmission cable routes cross deep water where 20th-century wartime losses occurred. Planning and development of infrastructure relating to renewables may also interact with significant built heritage and archaeology on the foreshore and coast edge.