Subir Sarkar, the head of the geography department in North Bengal University, offered two plausible reasons for the early landslides.
“A triggering mechanism, like the raion, is needed for a landslide to occur. But this time, the rainfall was neither heavy nor of greater intensity, which suggests the threshold level (for the landslides to occur) has been disturbed. The other reason could be that the (landslide) preventive measures were not put in place before the onset of monsoon,” Sarkar said over the phone from Siliguri.
The preventive measures Sarkar refers to include jhora-training to reduce the velocity of water, cleaning of drains to ensure smooth flow of water downstream and construction of channels to guide torrents away from vulnerable areas. Experts agree that the man-made causes for landslides include grading, terrain cutting and excessive development.
About the new locations of landslides like Birick, which did not have any past history till last week, experts were not willing to comment without visiting the spots.
Praful Rao, the president of Save The Hills, said the concern was that the mudslips have occurred after a long dry spell, and not at the end of the monsoon when the earth is saturated with water and the hills are vulnerable. “This is why most major landslides in the past had occurred in September which is the fag end of the monsoon,” Rao, whose NGO works on landslides, said.
It is an accepted fact among most experts that landslides occur in areas where the terrain has been altered for the construction of roads, houses and other utilities. “The frequent landslides at 27th Mile is because of the construction of the hydel project on the river Teesta in the area,” alleged a member of an NGO which had opposed the project since its planning stage.
Admittedly, the scale of the recent landslides in most of the places is not big barring the one at Birik, 45km from Siliguri, on NH31A on Friday. The Birik landslides (there was one on Sunday night as well), most agree, may have occurred because of a combination of human and natural factors: cutting of the hillside and the rains.
The BRO, which is widening the road at Birik as part of its project to double-lane NH31A that connects Sikkim to the rest of the country, said once the work is completed, retention walls would be constructed along the hillside as a protective measure against landslides.
“The area is among the 28 identified troubled spots between Sevoke and Teesta. However, we are confident that once we complete our work, landslides will not pose much of a problem in the area,” said a BRO sources.
Even this evening, traffic was moving in a single file at Birick with the debris yet to be cleared.