Overview:
Seven people were killed in a failure that was probably caused by undercutting of the slope and triggered by heavy rainfall.
The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
On 18 April 2023, a destructive rockslide hit the border town of Torkham in Khyber Pakhtunkhwa province in NW Pakistan. I blogged about the Torkham Rockslide at the time, speculating that undercutting of the toe of the landslide was likely to be the fundamental cause of the failure. In a new paper just published in the journal Landslides, Sana et al. (2023) provide an initial analysis of the accident.
The Torkham Rockslide struck an area that was primarily used for parking of trucks waiting to cross the border into Pakistan. The landslide occurred at about 3:40 am local time, burying about 20 trucks. Sana et al. (2023) report that seven people were killed.
The Torkham Rockslide occurred in a steep limestone cliff, as shown in the image below, from the paper. The landslide fragmented into large blocks that made the rescue operations very challenging:-
The authors undertook a field visit and have analysed satellite imagery and rainfall records. They conclude that the likely underlying cause of the landslide was road widening that involved cutting of the toe of the slope. The trigger is likely to have been heavy rainfall – the area had suffered a series of rainfall events through April 2023, and Sana et al. (2023) report that local people described a convective storm occurring at the time of the landslide.
Sana et al. (2023) recommend improved landslide mitigation measures along this important road, including better drainage, retaining walls, terracing, rockfall barriers and catch fences. I would agree, but would also suggest that establishing safe parking areas for trucks could help.
Reference
Sana, H., Ullah, R., Zinke, R. et al. 2023. Torkham Rockslide of April 18, 2023, in Pakistan: an interplay of geomorphology, geology, slope cutting, and climate. Landslides (2023). https://doi.org/10.1007/s10346-023-02164-x
