Why this research is important
The Oslofjord region is rich in archaeological sites and monuments. To efficiently manage this important heritage, to preserve it, study it and make it accessible to the public, cultural heritage agencies need cost- and time efficient routines that do not interfere with critical tasks such as for example the expansion of a railway network or urban planning.
Until recently, areas that might contain buried archaeological structures, for example the remains of burial mounds from the Viking Ages or medieval houses, were investigated by a method called “topsoil stripping”: the mechanical removal of ca. 15-20% of the uppermost layer of the ground in parallel trenches. This approach, however, is time-consuming and thus expensive, plus it can lead to sites being overlooked. Most importantly, though, it can destroy archaeological traces.
Another, non-destructive way to search for and investigate sites is the use of geophysical prospection devices such as the ground penetrating radar (GPR) with which we can scan the underground without the need to excavate. A modern, motorised GPR can investigate several hectares per day, providing us with information about large areas in a short amount of time. However, the electromagnetic waves that are being send into the subsurface by the georadar are influenced by environmental factors present at the study site, for example different soil and sediment types or the amount of moisture in the ground. For cultural heritage management, this means that for example buried archaeological structures might be well visible in georadar data obtained under dry conditions, while the same structures could become almost invisible when the data were collected after a period of heavy rainfall. Obviously, this can cause problems, as the results of our archaeological investigations and registrations need to be reliable. Until now, however, this issue has not been researched sufficiently, most probably because it is very complex, involving different fields of expertise including archaeology, geophysics and soil science.
What we will do
With a team consisting of researchers from Vestfold and Telemark County Council (VTFK), the Norwegian Institute for Cultural Heritage Research (NIKU) as well as experts from the Austrian Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology and the Norwegian Institute of Bioeconomy Research (NIBIO), the recently started project Environmental factors in minimal-invasive Cultural Heritage Management: The Vestfold Monitoring Project (VEMOP) aims to investigate this issue for the environmental factors present in the Oslofjord area. Over a period of 14 months, we will conduct repeated georadar prospections across four test sites, which will represent different sets of environmental factors as well as archaeological features frequently found in Vestfold.
In comparing the data sets collected at a specific test site under different conditions, e.g. during a dry period or after a heavy rainfall, we can determine which of these conditions serves best in revealing the archaeological structures we are looking for.
VEMOP started work at 1. November 2019. The first months were dedicated to researching projects who have undertaken similar endeavours. We also took some time to build up our reference group consisting of people from different stakeholder institutions, among them the Directorate for Cultural Heritage Management, the County Councils of Viken, Innlandet and Møre og Romsdal, the Universities of Oslo and Bergen and the Norwegian Institute of Bioeconomy Research, which will support us with their expertise. And we spent a lot of time discussing potential test sites across Vestfold.
During the next months, we will select four test sites and then prepare to equip them with the necessary measurement systems. This will require administrative work in order to get the necessary permissions from responsible agencies for test sites protected under the Cultural Heritage Act and from respective landowners as well as fieldwork to install the measurement sensors in the ground. Once these tasks are completed, we look forward to begin with the actual georadar surveys.