Seabed Prehistory

Wessex Archaeology was commissioned in April 2003 to undertake the research project ‘Seabed Prehistory – gauging the effects of marine aggregate dredging’, funded by the Aggregate Levy Sustainability Fund (ALSF). The project seeks to demonstrate the scope for assessing prehistoric archaeology that has been covered by rising sea levels.
 
The sands and gravels targeted by marine aggregate dredging form part of Britain’s historic environment. They have the potential to contain evidence of our predecessors’ inhabitation of Britain, now thought to have begun up to 700,000 years ago. There have been successive changes in sea level since then, resulting in dramatic changes in the landscape, with much of the now submerged sands and gravels indicating early river systems and coastlines. At different periods, these river systems and their flood plains would have formed part of landscapes occupied by the early prehistoric inhabitants of Britain and north-west Europe. It is these remnant prehistoric landscapes within the current seabed that may contain archaeological deposits and evidence of where and how our predecessors lived. Further information on submerged prehistoric landscapes is available.
 
Since the early 1990s the marine aggregate extraction permission process has required marine aggregate companies to prepare an Environmental Impact Statement (EIS) for each individual licence application. This statement addresses the potential impacts of dredging activity on all aspects of the marine environment, including the physical environment, fish and shellfish resources, fishing activity, navigation and the historic environment.
 
The archaeological component of an EIS assesses the form and character of predicted impacts on the historic environment. This involves evaluating now terrestrial prehistoric sediments (Palaeolithic and Mesolithic) which are now submerged and maritime archaeology such as shipwrecks and associated artefacts. The prehistoric archaeological potential of an area is characterised using survey data provided by the company undertaking an application and any literature or database sources that are relevant. On the basis of this assessment of archaeological potential, importance and predicted dredging impacts, appropriate mitigation is recommended.
 
Currently, the submerged prehistoric archaeology of a licence application area is assessed using a combination of sources, including models of north-west European prehistoric populations, models of palaeolandscapes and comparisons with evidence of Palaeolithic and Mesolithic activity from adjacent coastal areas. This material covers broad areas and is based on the extrapolation of a limited amount of archaeological evidence, which creates constraints when assessing specific aggregate applications to exploit relatively small areas. As a result, the palaeolandscape reconstruction necessary to evaluating archaeological potential, in particular, relies on the survey material collected by the marine aggregate company.
 
The archaeological consultant will generally receive survey data from the marine aggregate company to inform their assessment. However, the survey work undertaken by the aggregate company for an extraction licence application is primarily aimed at assessing the aggregate resource, and the survey strategy and specifications are therefore not always suitable for gathering data specific to archaeology.
 
The Seabed Prehistory project aimed to address this by developing methodologies for assessing and evaluating prehistoric seabed deposits in the course of licence applications. This involved directed geophysical and geotechnical surveys, geoarchaeological and environmental analyses and the integration of all data sources to produce reconstructions of palaeogeographies and environments.