Safeguarding Cultural Heritage: Integrating laser scanning, InSAR, vibration monitoring and rockfall/granular flow runout modelling at the Temple of Hatshepsut, Egypt

Abstract

Abstract. The predictive capacity for rockfall has significantly increased in the last decades, but complementary combinations of observation methods accounting for the wide range of processes preparing and triggering rockfall are still challenging, especially at sensitive sites like World Heritage monuments. In this study, we combine Terrestrial Laser Scanning (TLS), Interferometric Synthetic Aperture Radar (InSAR), ambient vibration analyses, and rockfall runout modelling at the 3500-year-old Mortuary Temple of Hatshepsut, a key World Cultural Heritage Site and among the best-preserved temples in Ancient Thebes, Egypt. The temple is exposed to a 100 m vertical, layered, Eocene Thebes Limestone cliff. Here, a major historic rock slope failure buried the neighbouring temple of Thutmose III, and behind the temple frequent fragmental rockfall occurs. The project “High-Energy Rockfall ImpacT Anticipation in a German-Egyptian cooperation (HERITAGE)” aims to combine TLS and InSAR to constrain pre-failure deformation, potential detachment scenarios, and rockfall runout modelling for singular blocks and granular flows from rock tower collapses towards an integrative analysis. Based on TLS and InSAR, we could measure volumes of small failures between 2022–2023 and map potential detachment zones of interest for larger failures. Only the combination of InSAR and TLS can unequivocally delineate rockfall-active areas without the ambiguity of single techniques. Based on this, we modelled the runout of small single-block failures of the observed size spectrum (0.01–25 m3) and constrained frictional parameters for large (i.e. > 103 m3) granular flows from collapsing towers using historic failures. The applicability of ambient vibration analysis to detect preparatory destabilisation of rock towers prior to deformation by frequency shifts is successfully tested. This study shows the potential of combining non-invasive rockfall observation and modelling techniques for various magnitudes towards an integrative observation approach for cultural heritage such as Egyptian World Heritage Sites. We demonstrate the capabilities of our integrated approach in a challenging hyper-arid climatic, geomorphological and archaeologically sensitive environment, and produce the first event and impact analysis of gravitational mass movements at the Temple of Hatshepsut, providing vital data for future risk assessments.