Conserving world heritage in climate change(d) futures: building understanding of precipitation impacts through innovative hydrological-based solutions

Abstract

Heritage landscapes are under threat from a change in precipitation regimes. However, there is little understanding of the surface and subsurface hydrological interactions of heritage landscapes. Establishing the surface and subsurface hydrological interactions will allow for a greater understanding of the potential impact that changes in rainfall could bring to heritage landscapes. It is important to understand these interactions to equip heritage practitioners to make informed decisions about site hydrological management and undertake interventions to create climate-enabled sites. This research aims to build a baseline to develop an understanding of surface and subsurface hydrological networks of three World Heritage Sites (WHS) in Scotland, Ring of Brodgar Heart of Neolithic Orkney, Rough Castle on the Antonine Wall, and St Kilda. In addition, this study examines the influence that key visitor features are having on the subsurface hydrology at Ring of Brodgar and Rough Castle through the novel application of Microwave Moisture Sensor (MMS). MMS highlighted the influence of footpaths and signboards across two heritage landscapes. At Ring of Brodgar, the main footpath influenced soil properties across a wide area to each side of the path, whilst a line of desire had a narrow impact on soil properties. At Rough Castle, the influence of main footpaths, signboards and lines of desire were well defined within the MMS data. With increased precipitation, the effects of footpaths on soil properties may become more pronounced and could be damaging to buried archaeology. Hydrological modelling was carried out using 0.25m resolution LiDAR data to determine the surface hydrological networks of three WHS sites. The hydrological networks at the Ring of Brodgar show the controlling influence of archaeology and footpaths. At Rough Castle, hydrological modelling demonstrated the full extent of the drainage of the fort top and the effect of archaeological defensive ditches on controlling the hydrology. On St Kilda, hydrological modelling shows the influence of upstanding archaeology on hydrological networks. All sites demonstrate the influence of upstanding archaeological features in the higher-order stream networks, and on St Kilda, the lower-order hydrological flows show the legacy of the cultivated farmland in controlling hydrological networks. Climate change precipitation projections (RCP 8.5) for each site were used in conjunction with hydrological modelling and MMS to suggest how sites may become affected through changes in precipitation. For Ring of Brodgar, this highlighted the possible increase in overland flow and the potential increase in soil saturation. For Rough Castle, the potential increase in standing water for longer periods and the erosion of the Antonine Wall and Ditch. St Kilda showed a potential increase in erosion surrounding upstanding archaeology and an increase in soil repellency. The application of MMD required further development but is suitable for understanding the subsurface interaction surrounding key visitor features. Hydrological modelling could be applied to any heritage landscape which has a suitable DEM/DSM from LiDAR data. Overall, this research has established a baseline approach for determining surface hydrological networks and the influence of visitor pressures on the subsurface in three WHS across Scotland, and in the wider heritage sector.