Urbanisation, the Real Villain in Landslides

Urbanisation, the Real Villain in Landslides

Over the past 50 years, landslides have become ten times more frequent and is set to escalate, owing to two increasing trends — climate change and urbanization. This finds mentioned in a major study that assess where and to what extent such risks, will rise.

The study published in Journal Nature explains that rapid pace of urbanization, especially in low- and lower-middle-income countries in tropical regions, will put more people in the path of landslides.  The researchers said that informal housing practices such as unregulated deforesting, slope cutting and household water drainage, could increase the chance of landslides.


In the report, the researchers say that more than 80 per cent of fatal landslides occur in the tropics. They added that heavy rain, often during cyclones and monsoons trigger this. Climate projections show that, on average, the intensities of tropical deluges could double by the end of the century. “But it’s hard to say what will happen in any given place,” the researchers said.


In the report, the authors point out that the first half of 2022 was one of the deadliest on record for landslides. “In January and February, cities across South America were hit by devastating soil, rock and mud flows — burying at least 14 people in their homes at Dosquebradas in Colombia, and killing 24 people in Quito, Ecuador, and at least 220 in Petrópolis, Brazil. In April, May and June, hundreds more were killed in Pilar in the Philippines, Durban in South Africa, Recife in Brazil and across Bangladesh,” the authors said.

The report also said that about 4,500 people are killed on average worldwide each year by landslides.


The researchers point out that the present landslide risk assessments fall short in a fast-changing environment. “Predictions at city or broader scales are often based on historical data — more landslides are expected to occur in locations similar to those where they happened before. Yet records are often poor or missing in low- and middle-income nations,” they said. Moreover, the researchers stated that environmental changes could reduce the usefulness of historical records for long-term projections.

Most of the time the causes and impacts, physical and social, are treated separately. Most of the time, the engineers tend to focus on stabilising slopes at specific sites. The city planners focus on enforcing regulations to prevent construction in landslide-prone areas. Apart from this, scientists give importance to examining people’s perceptions of risk.

However, the study says that disaster risk reduction experts need to consider ‘dynamic’ interactions between the natural environment, rainfall patterns and informal urbanization. They should consider the root causes and drivers of risk that push the most vulnerable people into hazard-prone locations — including economic and political inequalities, loss of sustainable rural economies and population growth, they added.

The researchers also said that human modifications to slopes could make them more likely to fail. “Cutting into them, for terracing or to flatten the ground for houses or roads, makes them steeper and thus more unstable,” they said. Apart from this, they also mentioned that removing plant cover and adding water through poor drainage or leaking pipes also increased the risk of landslides. The same comes with mining and the construction of roads and other infrastructure.


The authors in the study called on policy-makers and practitioners to use evidence-driven assessments to inform disaster risk reduction policies. They said that Disaster-risk assessments have advanced in the past decade owing to improved satellite and remote-sensing observations of global rainfall, land cover and information on landslides, as well as more accurate digital elevation models and open-data initiatives. However, the authors opined that the next stage is to capture slope features, soil properties, rainfall dynamics and urbanization processes at finer scales. These can be put into process-based models, they added.

“Process-based models can help disaster risk reduction consultants, city planners, engineers and those involved in community development to identify ‘low-regrets’, cost-effective solutions that holistically address interacting risk drivers under modelled scenarios, “they said. 

Decision makers should aim to use disaster risk reduction funding and policies to develop ‘pro-poor’ approaches to landslide resilience, by listening to and helping vulnerable people in their region. Reorienting city planning away from top-down approaches, towards joint government–community working groups is key.

The population is expected to increase, reaching 8.5 billion in 2030 with the half of the population virtually concentrated in urban areas. However,  the  rapid urbanisation is not always associated with acceptable quality standard of life. Researchers say that the pace of the city growth in developing countries has not given the opportunity to an adaptation from rural to urban system.


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