Rock instabilities at the archaeological site of Dadan (Kingdom of Saudi Arabia)

This paper provides a summary of the investigations carried out for the preliminary assessment of potential geohazards affecting the archaeological site of Dadan in the Kingdom of Saudi Arabia. The site is characterized by the presence of Cambro-Ordovician sandstone cliffs (Siq formation), which were quarried in ancient times (Dadan/Lihyan kingdom) for building materials. Both the steep quarried portion (Upper Siq) and the gentler underlying slope (Middle Siq) contain tombs of significant archaeological value. Landsliding and erosion are the main geomorphological processes affecting the site, posing risks to the safety of visitors, archaeological workers, and the preservation of the site. The primary processes affecting the rock cliffs, the underlying slope talus, and the tombs were identified using geological and geomechanical surveys, in addition to various geomatic acquisitions. The mechanical properties of the rock formations and discontinuity sets were identified through laboratory testing and in situ surveying, respectively. This information represents the first step in promoting further actions for risk mitigation and site management.