The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
A fascinating new paper (Corominas et al. 2025) has just been published in the journal Geoenvironmental Disasters that describes the compilation and analysis of a new dataset on fatal non-seismic rockfalls in Spain. The dataset extends back for 220 years – a remarkable feat in itself – although the detailed analysis focuses on a 150 year period between 1872 and 2021. Even better, the paper has been published open access and under a creative commons license, which means that the information can be widely circulated.
Over the period of the study, Corominas et al. (2025) identified 1,118 fatal rockfalls in Spain, causing 1,550 deaths. This is the occurrence with time:-
The reason for starting the analysis in 1872 is clear. It is always most interesting to look at the event rate (rather than the number of deaths) – the grey line – as this is less noisy.
It is notable that the rate has fluctuated considerably with time, but that there is a distinct increase in the last 20 years.
Corominas et al. (2025) have put a great deal of effort into understanding these trends. They correctly note that a fatal rockfall is the consequence of a complex interaction of a range of factors, which can include the topography, the climate, human modification to slopes and changes to vulnerability. To illustrate this, take a look at these two graphs, from the paper:-
As before, take a look at the event rate (the grey lines). In the case of quarries and excavations, the event rate has dropped very substantially in more recent years. This is the result of changes to regulation and practice in quarries – in other words, these locations have simply become safer. The authors describe this in some detail:-
“The reason must be sought in the operational changes introduced in the quarries. One hundred years ago, quarries and slope cuts were excavated with non-technical criteria or with poor engineering design. In our opinion, the observed decrease is due to improvements in excavation procedures and the adoption of occupational safety measures. These include the Regulation of Basic Mining Safety Standards in force since 1985 and the Occupational Risk Prevention Law in force since 1996. Studies on occupational and mining safety in Spain have highlighted the role of safety standards and safety measures and risk prevention in the substantial reduction of accidents.”
On the other hand, the event rate on roads has increased dramatically, although number of actual deaths shows no clear trend. A part of this might be better reporting – perhaps rockfalls in remote mountain areas are better reported than in the past. However, Corominas et al. (2025) note the following:-
“…[T]he vast majority of events occur in mountain roads, including those of the Canary Islands and the Balearic Islands. It is therefore logical to assume that the higher incidence is due to the increase in traffic on the most dangerous mountain road sections.”
And…
“The increase in the number of victims contrasts with the investment made by the administration in mitigation measures against rockfalls and the execution of road bypasses as mentioned in the previous section. This apparent lack of effectiveness of the set of preventive actions has been observed on other mountain roads … In any case, the trend of increasing accidents highlights the difficulty of risk management on roads that cross mountain ranges following the course of the main river valleys. These are stretches affected by a diffuse hazard originated far above the road and with innumerable source areas.”
Similar increases in events and losses were also noted in mountain trails and in coastal settings, which Corominas et al. (2025) ascribe primarily to changes in human activity – i.e. more recreational activities in the mountains and on the coast. As someone once put it to me, rather starkly, there are simply more targets in these locations than used to be the case.
This summary does no more than skate over the surface of a really fabulous piece of work. There s huge insight and richness in the data, demonstrating the complexity of these events. It would be fantastic to see more studies of this type.
Reference
Corominas, J., Lantada, N., Núñez-Andrés, M.A. et al. 2025. Fatal non-seismic rockfalls in Spain. Geoenvironmental Disasters 12 [17]. https://doi.org/10.1186/s40677-025-00317-9.
