DOWNHILL LANDSLIDE

Amitava Banerjee and Joydeep Thakur, HT, 12 Jul 2015: The recent landslides and the devastation caused by them in Darjeeling have left everyone with a fond memory of the Queen of the Hills in a despondent mood. ROLLING STONES Unplanned urbanisation and mining have destroyed the Darjeeling Hills The recent landslides and the devastation caused by them in Darjeeling have left everyone with a fond memory of the Queen of the Hills in a despondent mood.

Darjeeling and Sikkim are prone to landslides because of their complicated geological set-up. Data available with the Geological Survey of India reveal that the first recorded landslide in the Darjeeling-Sikkim region dates back to 1899. Since then, there have been innumerable landslides in the zone. Most of them went unnoticed and did not occur in or around any human habitat. In fact, the entire stretch of the Himalayas from Jammu and Kashmir to Arunachal Pradesh is prone to landslides. Altogether, nearly 15% of India’s landmass is prone to landslides.

“The Himalayas have always been prone to landslides because of several geo-environmental, morphometric and geomorphological factors, such as weak and sensitive slope-forming material, joints and fissures on hills, tectonic uplift and steeper slopes, to name a few. Human interference, such as mining, excavation, deforestation and artificial vibration also play important roles locally. Now, add to all this the fact that a landslide needs a triggering factor, like heavy and incessant rain or a major earthquake — as has been the case in Darjeeling, Sikkim and Uttarakhand,” said Saibal Ghosh, a landslide expert and superintendent geologist at the GSI’s Geohazards Research and Management Cell in Kolkata. But what makes Darjeeling and Sikkim stand out is that they are marked with ‘Blue’ colour on the GSI’s Landslide Vulnerability Map, indicating that it is the most hazardous zone in the entire country. Only a few other patches in Northeast and a narrow strip in Jammu and Kashmir match its vulnerability.

And there are reasons for this. Some are natural, such as the location of Darjeeling, which takes the first brunt of the monsoon. This area is also prone to earthquakes, which makes it all the more vulnerable because soon after an earthquake several landslides take place — as was seen after the Sikkim earthquake in 2011.

“In fact, one of the deadliest landslides that ever hit the Darjeeling and Sikkim Himalayas was in the year 1968 — when a torrential rainfall triggered a few hundreds of landslides, killing several people and breaching the Darjeeling-Sikkim road at numerous locations. The extent of the damage caused in 1968 was so huge that restoration of the roads took more than a year. And, at that time, there were definitely lesser human activities than what we have today,” Dr Ghosh said.

But a section of the experts says the cause of the recent spate of landslides in Darjeeling is mainly anthropogenic. Though natural phenomena, like earthquakes, do have a catalytic effect, it is the irresponsible intervention by humans that has been triggering more landslides in the Hills in recent times. Definitely, unplanned urbanization, deforestation, monoculture, mining and illegal stone quarrying are some of the main reasons responsible for the devastation, feel experts across the spectrum.

The explosion in human population has resulted in depletion of the forest cover. Rampant deforestation for agricultural land, new settlements and road connectivity, along with the increase in pollution levels have adversely affected the mountain’s eco-system and, in turn, the weather pattern.

“Earlier, we used to have constant heavy rainfall. Now, the intensity of rain has increased. There is usually a dry spell followed by intense rainfall over a brief period of time, thereby causing damage in the form of landslides. Geo-scientists claim that 50mm of rainfall in an hour is enough to trigger a major disaster in the Himalayas” Wing Commander (Retd) Praful Rao of Save The Hills, an NGO working in the landslide-hit areas, told HT.

On June 30, Kalimpong alone had registered 226 mm of rainfall (measured by Save the Hills) in 7 hours — which is around 30 mm of rainfall per hour. Again, on July 8, Kalimpong registered 93 mm of rainfall. “The rainfall was so intense that in the first one and a half hour, the total rainfall recorded was 57mm” Rao said.

Rampant construction of roads ,not well-designed wither, is another major cause of the landslides.

“The natural drain age system of the mountains is getting affected because of the badly engineered roads that cause landslides. Well-engineered roads with proper drainage system, which does not allow the water on the roads to stagnate, will definitely ease this problem,” Rao added.

The laying of fibre optic cables by cellular phone companies is also one of the main reasons behind the landslides this time. “The stipulated norms have not been followed while laying the cables. Pits were dug carelessly without paying any heed to the stipulated norms for the depth of the pits. The pits have also not been covered up and this resulted in huge amounts of water seeping in with heavy rain. At many places, drains got blocked. The stagnant water, therefore, found its way out from the hillside resulting in the landslides” Darjeeling’s MLA, Trilok Dewan, said.

Illegal mining is another major concern. Lowgrade coal is found in small quantities in areas around Tindharia in Kurseong sub-division and Nimbong area of Kalimpong sub-division. Such illegal mining of coal resulted in a huge landslide in Tindharia with the entire region being declared a sinking zone.

Incidentally, landslides washed away a 500-m stretch at

Paglajhora below Kurseong town on June 16, 2010. Altogether, 150m of road at Tindharia was washed away by landslides on September 28, 2011, resulting in the closing down of the Tindharia-Kurseong section of National Highway 55. It remains closed till now.

“Illegal mining of coal is rampant in the lower reaches of Nimbong. This sparked major landslides in 2007. There is also a mining racket in Malbazar in the Dooars, which oversees the extraction of coal in Nimbong. Interestingly, whenever a tea garden closes down in the Dooars, there is an increase in mining activity in the Nimbong area” Roshan Rai of DLR Prerna, another NGO, told HT.

Two GSI teams have been to Kalimpong and Mirik to undertake a detailed analysis of what triggered the landslides this time. Over the next one week, they will collect data related to at least 35 parameters that will help researchers zero in on the exact reason behind the tragedy.