Why landslides hit NE? GSI scientist Dr. Pankaj Jaiswal speaks to Northeast Live

Landslides are not uncommon phenomena in the Northeast. The region witnesses landslides that inflict small to large-scale destruction every now and then.

But what causes these landslides in the region? What are the root causes or what factors contribute to the frequent landslides? and what are the countermeasures to mitigate their impact?

Speaking exclusively to Northeast Live, Deputy Director General of Geological Survey of India, Shillong, Dr Pankaj Jaiswal, scientist shed light on the frequent landslides in the Himalayan foothills, pointing to the immaturity of the soil in the region as a key factor.

Dr Jaiswal said, “The maturity of the soil depends largely on its age. The lower part of the Himalayas or the foothills are very immature. If the rocks are immature, the materials are loose, making them highly sensitive to landslides. Any sort of human interference or natural disturbances in these areas can trigger more landslides compared to other landscapes.”

In every monsoon season, Sikkim and Arunachal Pradesh in particular, suffer extensively due to rain-triggered landslides.

Speaking about the measures to mitigate the high landslide risk in these vulnerable regions, the Geologist said, “Arunachal Pradesh and Sikkim have a typical Himalayan landscape. If the landslides are occurring along the cut slopes, they can be mitigated by treating these slopes with proper retaining structures and rock bolting the rocks.”

He said that cut slope failures along roads can be treated by use management such as town planning or construction of houses those areas.

He however said that it is difficult to treat each and every slope and every drainage all along but at least the risk of the landslide can be reduced if the road of a settlement can be properly treated.

Speaking about the extent of damage in case of earthquake-triggered landslides in the Northeast, he said that there are differences between, landslides triggered by earthquakes, seismic landslides and rainfall-triggered landslides.

“When there is an earthquake, you can observe more attenuation affecting different parts of the landscape compared to rainfall-induced landslides. Rainfall mostly affects mid-slope areas, while earthquakes cause more attenuation on the higher, steeper slopes and cliff parts. Earthquake-induced landslides tend to occur on a larger scale and are often characterised by rockfalls and rock slides.

“These landslides will occur more on the steeper scarps and slopes, causing extensive damage over a larger area,” he added.