SNOW AVALANCHES

RAJNI SHARMA:-

Landslides and snow avalanches affect the remotely located often isolated, small communities in villages or hamlets in the mountain regions of the country where external assistance takes time to reach in times of emergency when the normally difficult terrain and tracks, may become almost impossible to negotiate. Many a times, even the information about the occurrence of such events and the damage done takes days to reach the district and state headquarters. Because of these reasons, landslides and snow avalanches assume the status of major natural disasters even though the affected area and population may be rather small.

Mapping is a modem method to identify landslides prone areas and it has been in use in India since the 1980s. In this method, the vulnerability of different parts of a landslide-prone region is assessed in terms of past occurrences, steepness of slopes, conditions of rocks, and rainfall rates and the different areas are given “ratings” like Very High, High, Moderate, Low, Very Low, which indicates the likelihood of occurrence of landslides in those areas. Some of the regions for which such zonation mapping has already been completed or is nearing completion are the roads in Himachal Pradesh and Jammu & Kashmir particularly prone to landslides.

The Himalayas are well known for the occurrence of snow avalanches particularly the Western Himalayas i.e., the snowy regions of Jammu & Kashmir, Himachal Pradesh and Uttaranchal. Broadly speaking, an area of about 200,000 square kilometres in these three States is vulnerable to snow avalanche disasters. Snow avalanches also occur in the eastern parts of the Himalayas but the denser forest and vegetation cover on the eastern and the northeastern Himalayas (due to heavy rains in these mountains) act as binding force and inhibit excessive accumulation and slippage of snow mass. The western Himalayas have many vulnerable sites prone to snow avalanches where hundreds of lives are lost and the social and economic life is disrupted every year. The formation zones in this region are located between 3000 and 5000 metres height.

In Jammu & Kashmir, the most affected areas are in the higher reaches of Kashmir and Gurez Valleys, Kargil and Ladakh and some of the major roads there.

There is no doubt that anything that comes in the way of a landslide or snow avalanche will suffer severe damage and may even be totally buried or wiped out. Anything located on top of a landslide will also not survive when the rock or mud slips out from below it.

Increased population, spurt in quarrying, mining and construction activities near unstable hill slopes, ill-conceived developmental activities in the vulnerable hilly areas, have resulted in more landslides and greater damages.

Landslides are also known to result in blocking of streams or overflowing of lakes thus causing flash floods because large volumes of debris falling in a lake or reservoir cause its water to overflow or the temporarily blocked stream may suddenly release the huge quantity of impounded water to cause a devastating flash flood downstream.

In case of specific kinds of snow avalanches, the resultant damage is quite characteristic. For example, the “slab” type snow avalanche, in which massive slab or slabs of hardened snow come hurtling down, me hit is very hard and smashes anything that takes the hit. It is on record Aat in 1975, a group of mountaineers climbing the Dhaulagiri region of the Himalayas saw a massive “mattress” of snow 15 metre thick poised for collapse as a slab type snow avalanche.

On the other had, “loose snow” kind of snow avalanche covers a large area. Due to the fragile nature of the rocks of the still-growing Himalayan mountains, the snow avalanche may ‘also carry large quantity of debris comprising loose soil, small stones, and large boulders. ”Airborne” avalanches occur on the slopes of the greater Himalayas and are one-of the most devastating kind affecting large areas in the valleys.

Reduction of losses (life as well as property) would by itself be so the basic question behind any possible relief is how might the losses on account of landslides and snow avalanches (or any other natural disaster for that matter) be reduced.

This can be achieved through the four fundamental steps i.e reduce the forces of nature or their intensity to the extent practicable, channelize or divert the forces of nature as much as possible, prepare, plan and warn to the fullest extent, rehabilitate and reconstruct quickly and wisely.

Measures for the rehabilitation of a community affected by landslide or snow avalanche will depend very much on the extent of the damage done by the disastrous event.

If the damage has not been severe, me rehabilitation will take the form of short-term relief to restart normal activities and taking long-term measures so that any future landslide or snow avalanche does not hurt the community at all or at least, not as much.

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