The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
I thought it would be useful to provide an update on the pattern of fatal landslides in 2024 to the end of May. Clearly, in the aftermath of the terrible 24 May 2024 landslide in Papua New Guinea, this has been a high profile issue over the last fortnight. There have been some very good articles written about the background causes of that particular event, and of landslides more generally.
So, as a reminder, my data is for fatal landslides only, and in this case I am using landslides to describe all mineral-based mass movement phenomenon, including rockfalls, debris flows and mudflows. I don’t include snow avalanches, and in this analysis I don’t include landslides triggered by earthquakes. There are references at the end of this post that describe the science of this data.
The graph below shows the cumulative total number of fatal landslides that I’ve recorded in 2024 to date, calculated in pentads (five day blocks). This data is to 30 May 2024:-
I’ve included two typical previous years – 2018 and 2019 – so that it’s possible to compare 2o24 with more typical years.
The data show that 2024 continues to run exceptionally hot in terms of fatal landslide occurrence. As regular readers will know, the key global period for fatal landslides is the northern hemisphere summer and early autumn (late June to end of September) – the steepening of the graphs, showing the higher rate of fatal landslides, in the period from about day 180 is clear in 2018 and 2019.
This year has seen global fatal landslides running at that higher rate since about day 100, and there was also an earlier period of high incidence.
To give an alternative comparison, this graph shows cumulative fatal landslides by month (i.e. month 5 is May), for 2024 (in black), with all previous years in the dataset plotted in grey:-
As the above data shows, 2024 is an extraordinary outlier – there is no previous year like it.
Of course this data continues to ask the question as to why we are seeing this pattern. That needs a much more detailed analysis, but most of these landslides are triggered by high intensity rainfall events. The obvious linkages are to global surface air temperature and to global sea surface temperature, both of which are also running at unprecedented levels. The hypothesis would be that these anomalies are generating more intense rainfall, which is being reflected in the landslide data.
We now move into the most interesting time of the year for fatal landslides. The key questions now will be the strength of the South Asia monsoon season and the pattern of landfalling tropical cyclones, which will determine how many landslides occur across Asia. I’ll watch with great interest.
References
The research that sits behind this data, and the analysis of earlier fatal landslide patterns, can be found in:
Froude, M. J. and Petley, D. N. 2018. Global fatal landslide occurrence from 2004 to 2016. Natural Hazards and Earth System Sciences, 18, 2161-2181, https://doi.org/10.5194/nhess-18-2161-2018.
Petley, D.N. 2012. Global patterns of loss of life from landslides. Geology 40 (10), 927-930.