A growing number of displaced people are settling in mountain regions prone to slow-moving landslides, those that move between 1 millimeter (.04 inches) and 3 meters (9.8 feet) per year. A new study offers a global assessment of how the pressures of human settlement increase exposure to such landslides.
As people migrate from rural to urban areas in search of work or to flee conflict, some settle in areas susceptible to slow‐moving landslides. The same is true of people driven away from lower-lying areas prone to floods. The study notes that poverty, among other things, often forces communities to high-hazard areas.
A team of 18 researchers compiled a global database of 7,764 slow-moving landslides across nine mountainous regions worldwide. The most densely inhabited landslides were in northwestern South America and southeastern Africa.
Slow-moving landslides rarely claim lives but they can cause significant damage to buildings and infrastructure.
“Most landslides are a sudden failure and cause damage rapidly to a small area. Slow-moving landslides on the other hand, affect a large area with a potential of removing whole villages,” Manabendra Saharia, an assistant professor of civil engineering at the Indian Institute of Technology, Delhi told Mongabay over email. Saharia is not associated with this research.
Another study on a similar topic focused on the Arno River Basin in central Italy found slow-moving landslides are responsible for roughly 7 billion euros ($7.6 billion) in total damage. Despite the risks, urbanization and uphill migration to avoid flooding are pushing people in the region to settle on unstable slopes. The same holds true for parts of the North American West and southeastern Africa where flooding has led to an increase in landslide areas inhabited by settlements.
Slow-moving landslides are often overlooked in assessments of landslide risk, and this lack of data makes it challenging to managing exposure, the study notes. The researchers highlighted four regions where data are particularly scarce: northeast Africa, northwestern South America, southeast Africa and the Tibetan Plateau. This lack of information may leave vulnerable communities unknowingly at risk to slow‐moving landslides.
The study notes there are ways to mitigate risk from slow-moving landslides. In East Asia and western central Europe, for example, researchers found that the number of settlements decreases with accurate mapping of slow‐moving landslides, which allows settlers to better manage their exposure.
In Japan, which accounts for nearly half of the data set in the East Asia region, a combination of structural and nonstructural measures, including erosion control measures, “has been effective in mitigating negative impacts of landslides,” the study states.
Saharia noted that this study could be useful to other mountainous countries facing similar threats.
“India has faced similar problems recently in Joshimath [in the Hindu Kush mountains bordering the Tibetan Plateau], and the information from this study might help develop policies,” Saharia said.
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