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Wednesday, July 1, 2015

landslides kill scores of people in Darjeeling

A landslide is the movement of rock, debris or earth down a slope. They result from the failure of the materials which make up the hill slope and are driven by the force of gravity. Landslides are known also as landslips, slumps or slope failure. The movement of landslide material can vary from abrupt collapses to slow gradual slides.  Sudden and rapid events are the most dangerous because of a lack of warning and the speed at which material can travel down the slope as well as the force of its resulting impact. Landslides can be triggered by natural causes or by human activity. They range from a single boulder in a rock fall or topple to tens of millions of cubic metres of material in a debris flow.

The sad news is the reported killing of scores of people due to landslides triggered by heavy rains in India's tea-growing region of Darjeeling.  According to reports, rescuers were digging through debris looking for survivors after landslides struck homes in Mirik, Kalimpong and Darjeeling towns in West Bengal state.  More people are feared trapped under mounds of mud and debris. Roads and communication links have been extensively damaged, officials said.

Incessant rains in the area for the past couple of days caused the landslide, states BBC. Thousands of tourists are now stuck in the picturesque hilly area, its correspondent adds. The landslides have brought down a number of homes on the slopes of the hills, news agency AFP quoted a Police official as saying.

Darjeeling district, which attracts thousands of tourists every year, is about 600km (372 miles) north of the state capital, Kolkata (Calcutta). In 1968, a torrential rainfall had unleashed about 20,000 landslides, killing thousands and breaching the Darjeeling-Sikkim road at more than 90 places.  The presence of coal quarries have always added apprehension to their repeating and many have been suggesting afforestation on the slopes.  Planting vegetation on the landslide prone areas is considered a line of defence.  Another social measure is  the banning of cattle grazing in these spots.

Sad that another force of nature has killed people.  The Fire Policy [as envisaged under the Standard Fire and Special Perils Policy in India]  covers the perils of “Subsidence and Landslide including rockslide”.  The perils covered under this head are described as :

VIII: Subsidence and Landslide including Rock slide : loss, destruction or damage directly caused by Subsidence of part of the site on which the property stands or Land slide/Rock slide excluding :
a)     the normal cracking, settlement or bedding down of new structures
b)     The settlement or movement of made up ground
c)    Coastal or river erosion
d)    Defective design or workmanship or use of defective materials
e)    Demolition, construction, structural alterations or repair of any property or ground works or excavations

As stated earlier, a landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability.  Landslides occur when the [slope stability|stability of a slopes] changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include: ground water pressure, absence of vegetative structure, erosion, weakening, earthquakes, volcanic eruptions.  Landslides are aggravated by human activities,  like - deforestation, cultivation and construction, which destabilize the already fragile slopes, vibrations from machinery, blasting, earthwork altering the shape of slope.

Subsidence is the motion of a surface (usually, the Earth's surface) as it shifts downward relative to a datum such as sea-level. 

At every step Nature does good things to Mankind but also makes him realize quite often that when it unleashes its power, it could be too devastating !

With regards – S. Sampathkumar
1st July 2015.
Landslide in Pak – photo credit : Boston Big Pictures.

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