2019 Yearbook

R E V I E W A N D A N A L Y S I S 27 HES’ digital documentation team undertaking a terrestrial laser scanning survey at Skara Brae to capture digital scans of the site and surrounding coastline (Photo: Historic Environment Scotland) water springs’, MHWS) remained stable for much of the 20th century in the vicinity of the Skara Brae sea wall but this may mask long term trends and the impact of wave erosion above and below the high tide level. Aerial imagery clearly demonstrates that without this defence, part of the site may have already been lost to coastal erosion and it is likely that the sea wall is contributing to increased rates of erosion on the unprotected soft- coast on either end and in front of the protected area. HES began a digital monitoring programme for the site several years ago. Every two years, we now undertake a terrestrial laser scanning (TLS) survey of Skara Brae and its surrounding beach to capture mm-scale accurate digital scans of the site and surrounding coastline. Comparing these TLS surveys with other data, it appears that MHWS has not eroded further inland than its 1900 position. However, the TLS survey provides much more detail, showing modest build-up of sediments in the active central area of the bay to the north of the sea wall. The accumulation of sediment is thought to be sourced from erosion of both the crest of the beach and from the lower foreshore. While the stability of the upper beach is good news, the losses elsewhere are a concern, and highlight the value of multi-year detailed three-dimensional analyses. While coastal erosion remains a threat to the long term survival of the site, the results of Dynamic Coast along with our own monitoring regimes indicate that the existing sea defence continues to fulfil its function of protecting the site. Regular monitoring and enhancement will continue, and the Bay of Skaill is a case study in the ongoing, second phase of Dynamic Coast, which incorporates further data from LiDAR (a 3D aerial survey method which uses pulsed laser light). HES is working closely with the Dynamic Coast team to combine available data sets at a variety of scales to enhance our understanding of the processes at work and the site’s vulnerability. This is informing our plans for management of the site and any future interventions will be underpinned by this robust analysis, taking full advantage of the potential of technological developments. Mairi H Davies is climate change manager at Historic Environment Scotland. Previously an inspector of ancient monuments, she is one of the principal authors of HES’ 2018 volume on climate change risk assessment for the HES Estate.