New research on the number of deaths caused by landslides may be key to understanding their global impact and managing them in order to save lives, according to Prof Dave Petley, a global expert on landslides and Executive Director of the Institute of Hazard, Risk and Resilience in Durham University, UK.
Petley examined nine years of rainfall-induced landslide events from the Durham Fatal Landslide database, a global record of losses of life from landslides that is maintained by the International Landslide Centre at Durham University. From 2004-2010 he recorded over 2,400 non-seismic landslide events, many of them concentrated in Asia and South America. These landslides were responsible for over 32,200 deaths, far more than had been previously understood.
Spatial distribution of landslides triggered by rainfall during the period 2004 to 2010 inclusive
In addition, another 49,000 people were killed by landslides triggered by earthquakes over the same period. In parts of the world regularly exposed to landslide hazards the number of landslide fatalities can be shown to rise as the population density increases. “This is a serious warning for the future, because in
Asia for example the population over the next 30 years is expected to increase by about 500 million people”, said Petley.
The sizes of landslides, as measured by the number of deaths, follows what is known as a power law relationship, meaning that the ratio of small, medium and large landslide events stays remarkably consistent from year to year. Power laws have long been known to describe landslide areas and volumes, but this is the first time that they have been shown also to apply to the number of people killed in each event. This is potentially very useful in the assessment of the likely impact of future landslide events, such as those caused by earthquakes and large storms.
Road cut off by landslide debris in Pakistan
However, the nature of these ratios varies according to location, suggesting that local factors may be important. Petley suggests that the size of households may be a key factor in determining this ratio for each region. Understanding the power law relationship can be very helpful for risk analysis and mitigation.
However, before this can lead to planning that could save lives, Petley says more research is needed to analyse the statistical distributions for fatality datasets for all landslide events in order to forecast potential losses of life. “Without landslide management, fatalities caused by landslides are likely to continue to increase. Unfortunately, we are losing the battle against landslides in mountainous, less developed
countries”, he said.
Contacts and sources:
Prof Dave Petley
Institute of Hazard, Risk and Resilience in Durham University, UK.
American Geophysical Union