Quantifying erosion of ‘at risk’ archaeological sites using repeat terrestrial laser scanning

Abstract

Effective heritage management is reliant on an understanding of the range of current and potential future threats facing archaeological sites. Despite this, the processes leading to the loss of in situ archaeological remains are still poorly understood, including the rates, timing and drivers of surface erosion. This issue is particularly significant for abandoned historical metal mines in upland landscapes, where erosion rates are typically higher due to a combination of the unstable character of the archaeological deposits and the increased effectiveness of surface erosion processes. This study utilises repeat terrestrial laser scanning (TLS) to monitor the changing condition of two adjacent lead mines in the North Pennines, UK, over an 18month period. The high spatial and temporal resolution of the TLS data, in conjunction with land cover characteristics derived from an unmanned aerial vehicle (UAV) survey, allows the detailed quantification of the causes and impacts of surface change. The results demonstrate that stream bank erosion is the process responsible for the most widespread and archaeologically significant damage, although localised gullying of mine waste heaps resulted in the largest volumetric loss of material (>160m3). Temporal variation in the erosion of upland archaeological sites is highly episodic, being dominated (>70%) by high magnitude but low frequency storm events. These results provide invaluable information regarding the causes and impacts of erosion of upland archaeological remains, as well as establishing a proven methodology which can now be applied to archaeological sites in other landscape contexts.