- 1School of Civil and Environmental Engineering, the University of New South Wales, Sydney, Australia
- 2Department of Geology, Tri Chandra Multiple Campus, Tribhuvan University, Nepal
- 3Istituto di Ricerca per la Protezione Idrogeologica, Consiglio Nazionale delle Ricerche, via Madonna Alta 126, 06128, Perugia, Italy
Active tectonics and high precipitation in Central Nepal Belts cause frequent rockfalls. This has caused severe impacts on communities and infrastructure, especially road networks. The major roads in Central Nepal, particularly the Pasang Lhamu Highway (PLH) and Galchhi-Rasuwagadhi Highway (GRH) have faced significant challenges due to rockfalls triggered by the 2015 Gorkha earthquake and seasonal high rainfall. These rockfalls obstructed transportation, and impeded road development and environmental management. Despite existing landslide susceptibility studies, limited research has focused specifically on rockfall susceptibility in the area.
This study addresses this gap by employing a physically based model, STONE [1], to assess rockfall susceptibility along these highways in the Rasuwa district. The model analyses individual rock blocks originating from user-defined locations, following independent paths influenced solely by gravity, and it is suited for assessing rockfall susceptibility along linear infrastructure [2]. To run the model, we used a 12.5 m resolution ALOS PALSAR digital elevation model and field investigation to prepare a rockfall source inventory. The second relevant input of the model is a map of locations for possible rockfall sources. Following Refs. [3], we obtained a probabilistic map of sources considering slope angle, relief, and vector ruggedness to establish numerical morphometric thresholds calibrated with observed rockfalls, and generalized the findings to unsurveyed sections across the whole study area. Next, we employed the STONE model to simulate three-dimensional rockfall trajectories and generate a rockfall susceptibility map.
The resulting map shows classified road segments into five susceptibility levels [4], with a susceptibility index ranging from 1 (low) to 5 (very high). Results highlighted high-susceptibility areas in Ramche, Dandagaun, and Syaprubesi, highlighting the segments of both highways most vulnerable to rockfall. As no rockfall protection strategies were adopted in these areas, which has affected road management and degraded the surrounding environment, results of this study would help to prioritize the sections of linear infrastructure that requires detailed rockfall studies and safety measures.
References
[1] Guzzetti et al., Comp. Geosci. (2002) https://doi.org/10.1016/S0098-3004(02)00025-0
[2] Alvioli et al., Eng. Geol. (2021) https://doi.org/10.1016/j.enggeo.2021.106301
[3] Alvioli et al, Geom. Nat. Haz. Risk (2022) https://doi.org/10.1080/19475705.2022.2131472
[4] Pokharel et al., Bull. Eng. Geol. Env. (2023) https://doi.org/10.1007/s10064-023-03174-8
How to cite: Pokharel, B., Lim, S., Nidhi Bhattarai, T., and Alvioli, M.: Implementing a physically based model to assess rockfall susceptibility in central Nepal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20950, https://doi.org/10.5194/egusphere-egu25-20950, 2025.
