From Pre-Failure Deformation to Runout: Integrating TLS, InSAR and Runout Modelling to Quantify Rockfall Hazards at the Temple of Hatshepsut, Egypt.

The predictive capability for rockfall hazards has improved markedly in recent decades; however, integrating complementary observation methods that capture the full range of preparatory and triggering processes remains challenging, particularly at highly sensitive sites such as World Heritage monuments. This study presents a multi-method assessment of rockfall activity at the 3,500-year-old Mortuary Temple of Hatshepsut in Ancient Thebes, Egypt, one of the best-preserved temples of Pharaonic Egypt. The temple is situated directly beneath a ~100 m high, layered cliff of Eocene Thebes Limestone, which is affected by frequent fragmental rockfall. A major historical slope failure in the vicinity previously buried the neighbouring Temple of Thutmose III, highlighting the long-term hazard potential.

Within the framework of the German–Egyptian project High-Energy Rockfall ImpacT Anticipation (HERITAGE), we combine Terrestrial Laser Scanning (TLS), Interferometric Synthetic Aperture Radar (InSAR), and numerical rockfall runout modelling to characterise both recent activity and potential future failure scenarios. TLS and InSAR data acquired between 2022 and 2023 enabled the quantification of volumes associated with small-scale failures and the mapping of potential detachment zones relevant for larger instabilities. The joint application of TLS and InSAR proved essential, as only their combination allows an unambiguous delineation of rockfall-active areas, reducing the uncertainty inherent to individual techniques. Exploratory ambient vibration analyses were applied on selected rock towers to test their applicability for detecting preparatory destabilisation by frequency shifts.

Based on the observed failure inventory, we modelled runout trajectories for single-block failures covering a volume range from 0.01 to 25 m³. In addition, frictional parameters for large-volume (>10³ m³) granular flows resulting from rock tower collapse were constrained using evidence from historical slope failures. These simulations provide first-order estimates of impact areas and energy distributions affecting the temple complex.

Overall, this study demonstrates the value of integrating non-invasive observation and modelling techniques across multiple failure magnitudes within a unified framework. The approach is particularly suited to hyper-arid, geomorphologically complex, and archaeologically sensitive environments. We present the first event-based and impact-oriented analysis of gravitational mass movements at the Temple of Hatshepsut, providing essential baseline data for future hazard and risk assessments at Egyptian World Heritage Sites.