In 2015, a landslide in China’s Guangdong province swept more than 70 people to their deaths. Triggered by heavy rains that saturated the soil under a pile of construction waste that had been precariously perched on a hill for more than 2 years, the landslide rushed through an office park in the city of Shenzhen. It crushed office buildings, enveloping them in mud up to 11 meters deep in a debris field that spanned roughly 70 football fields.
This event does more than highlight the deadly nature of landslides, hundreds of which occur every year around the world. It brings into focus an emerging new class of landslides: those triggered by human activities.
Researchers now have an idea of how many such landslides are occurring around the globe. They have compiled the most comprehensive database of landslides that took place between 2004 and 2016. This database includes information on the landslides’ causes as well as their death tolls.
The records reveal an uptick in the frequency of human-caused fatal slides, a worrying trend given the increasing prevalence of landslide-causing activities such as construction, illegal mining, and hill cutting.
Nearly 5,000 Landslides
Melanie Froude, a geographer, and David Petley, an Earth scientist, both at the University of Sheffield in the United Kingdom, assembled the database from reports of fatal landslides. The researchers tabulated 4,862 distinct landslides, which were responsible for, in total, 55,997 deaths, the team reported last week in Natural Hazards and Earth System Sciences.
“Collecting these reports and organizing them into a database shows us where landslides are frequently harming people, what causes these landslides and whether there are patterns in fatal landslide occurrence over time,” Froude told Eos.
An alarming trend stood out in the data: more than 700 of the landslides could be directly linked to human activities like construction, illegal mining, and hill cutting. These landslides were responsible for a total of 3,725 deaths.
What’s more, the prevalence of landslides associated with a human fingerprint has increased several percent, on average, each year since 2006.
Unstable Slopes Spell Disaster
The scientists also found that landslides were unevenly distributed geographically: more than 75% of landslides occurred in Asia. “The combination of tectonics and climate in Asia creates extremely active landscapes,” Froude said.
Mountainous regions in Asia are particularly susceptible to landslides, Froude added. “As settlements expand to accommodate more residents, competition for land forces the poorest members of society to occupy steep, unstable slopes.”
And as more people live in steeper areas, the more likely it is their behaviors will influence the stability of the slopes around them, the researchers explained.
Unsurprisingly, Froude and Petley found that the overall frequency of landslides was correlated with rainfall. For instance, landslides were more frequent in southeast Asia during the summer monsoon season. However, the researchers noted that more data need to be collected before it will be possible to potentially link landslide incidence with climate change trends.
“This article is an important contribution quantifying the scope of landslide impacts around the world,” said Jonathan Godt, a landslide scientist with the U.S. Geological Survey in Golden, Colo., who was not involved in the research.
Research, Regulations, Education
This month, Froude and Petley plan to release their database online. They’ve already created a map showing where landslides in their database have occurred.
Froude highlights that additional research, regulations, and education will be useful for preventing future human-caused landslides. “We need to refocus our efforts globally on preventable slope accidents.”