Complete information on the Landslides and Snow avalanches in India

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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.

Vulnerable Areas, Frequency and Intensity

Landslides: Landslides are a frequent and recurring phenomenon in the various hill ranges of India from Kerala to the Himalayas. Areas prone ID landslides include the Eastern and Western Ghats, the Nilgiris, the Vindhyachals, the mountains in the northeastern States and the great Himalayan range. The incidence of landslides in these regions is a recurring feature especially daring and after spells of heavy rains.

Landslide Zonation 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 indicate the likelihood of occurrence of landslides in those areas. Some of the regions for which such zonation mapping has already be-en completed or is nearing completion are :

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North Sikkim

Kathgodam-Nainital
Garhwal Himalayas including Yamuna Valley

Satluj Valley in Himachal Pradesh

The roads in Himachal Pradesh, Jammu & Kashmir and uttarancnaiar’ particularly prone to landslides. The phenomenon assumes alarming proportions in the hill districts of north Bengal, Sikkim and the northeastern States.

Snow Avalanches:

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The Himalayas are well known for the occurrence of snow avalanches articularly 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 tlje 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. In Himachal Pradesh, the vulnerable areas are : Chamba, Kullu, Lahoul-Spiti and Kinnaur. Specific villages highly prone to snow avalanches have been identified in these districts of Himachal Pradesh. In the Garhwal Himalayas in Uttaranchal. parts of Tehri-Garhwal and Chamoli districts suffer from snow avalanche problem. Just as zonation mapping is done for areas vulnerable to landslides, Zone Planning is done for snow avalanche sites and three types of zones are identified pertaining to the frequency and intensity of snow avalanches around an avalanche site. In other words, Zone Planning provides a means to assess the anticipated danger due to snow avalanches at the vulnerable site. The three types of snow avalanche zones are :

1. Red-Zone: The most dangerous zone where snow avalanches are most frequent and have an impact pressure of more than 3 tonnes per square metre.

2. Blue Zone: Where the avalanche force is less than 3 tonnes per square metre and where living and other activities may be permitted with construction of – safe designs but such areas may have to be vacated on warning.

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3. Yellow Zone: Where snow avalanches occur only occasionally.

Kind and Magnitude of Damage

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.

Landslides: More often, the major landslides are combinations of rockslide and rockfall. They all involve movement of mass (soil, debris or rock). The process of movement of mass may vary from slow soil creep to abrupt and sudden rockfall. Landslides, also known as landslips, range from low angle and rather slow slides to sudden vertical falls.

Based on the type of movement, relative rate of movement and kind of material involved, landslides can be designated into 5 kinds as follows:

  • Slump with earth flow
  • Debris slide
  • Debris fall
  • Rock Slide
  • Rock fall

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Landslides, being more widespread in different mountainous or hilly regions of the country (as against snow avalanches which are confined to the snowy regions of the Himalayas), cause damage which is more varied and more widespread. 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. Apart from the catastrophic damages suffered by communities living on or near unstable hill slopes as their houses along with persons and property may be destroyed by a landslide, the most crippling damages due to landslides are suffered by (i) roads and (ii) productive soil. Damage to roads leads to considerable inconvenience and economic loss. The disappearance of land and the cultivable top soil takes away the agricultural potential of the affected area thus depriving them of their already meager livelihood.

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.

Snow Avalanche:

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.

Relief Steps Taken

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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 following four fundamental steps:

a. Modify the Cause, i.e., reduce the forces of nature or their intensity to the extent practicable,

b. Modify the Hazard, i.e., channelize or divert the forces of nature as much as possible.

c. Modify the Loss Potential, i.e., prepare, plan and warn to the fullest extent,

d. Modify the Impact, i..e., rehabilitate and reconstruct quickly and wisely.

In the particular context of landslides and snow avalanches, we can achieve (a) above to some extent by artificial release of landslides at weak points and by blasting off unusual accumulations of snow and by building protective fences and restraining structures such as “cribbing” or “piling” at sites known for landslides or snow avalanches. Modification of hazard as mentioned at (b) above can be done by reopening the flow of water in a stream blocked by a landslide or snow avalanche before it assumes the dangers of a flash flood. Modifying the loss potential (Item “c” above) needs long term preparation and constant vigilance. These would involve awareness of hazard and landslides and snow avalanche, formulation of forecasts, arrangements to receive and disseminate warnings, and action plan to face the hazard when it occurs. The final item (d) above pertains to relief steps immediately after the event, i.e., to rehabilitate and reconstruct quickly (to reduce hardship to the affected community) and wisely (to reduce the adverse impacts during any future recurrence of disaster).

Essentially, the relief steps comprise the following :

1) Search and Rescue

2) Medical assistance to the injured

3) Disposal of the dead

4) Food and Water

5) Emergency shelter for the homeless

6) Opening up access roads if blocked; and restoration of communication channels

7) Psychological counselling of the survivors who have lost their close relatives

8) Repair of houses and facilities

9) Assistance (technical and financial) to restart economic activity to restore regular work and income .

10) Reconstruction through proper planning.

Measures for Rehabilitation

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 (a) short-term relief to restart normal activities and (b) 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.

1) Reducing the hazard proneness of the site through engineering measures such as strengthening or modifying the slopes, removing fragile and unstable portions, securing snow accumulations by snow fences, snow nets or by cribbing, and improvement of drainage.

2) Stopping indiscriminate quarrying and mining in mountain areas.

3) Afforestation of zones prone to landslides and “snow avalanches so that trees and vegetation provide a binding force to prevent slippage of debris, rock, and snow.

4) Creation of a voluntary, community-based preparedness-system of watch, monitoring and alert. This will not only be useful in times of a disaster but will provide enough self-confidence (and thereby self-reliance) which is an essential objective of an effective rehabilitation programme.

5) Provision of assistance for economic rehabilitation by arranging work, employment, loans, and grants.

In the extreme case of severe damage to a community by a landslide or snow avalanche, the site may be rendered totally unusable. In that case, rehabilitation takes the form of relocation and reconstruction. In such an event, .the new site should be carefully chosen so as to minimize vulnerability and risks.

GOVERNMENT RULES

The responsibility to deal with landslides and snow avalanche lies with the State Government. The Central Government moves in to assist the State Government depending on the seriousness of the situation. The District Administration (the District Collector) is the nodal functionary on behalf of the State Government and they can requisition the assistance of the Defence Services should the situation warrant it.

However, there seem to be no government rules as such specifically for landslides and snow avalanches. When these occur, these are treated as a natural disaster and dealt with accordingly. Most of the actions lie in providing short-term relief and rehabilitation to the affected communities.

Landslides and snow avalanches have been receiving considerable attention in research mode by central agencies such as the Department of Science & Technology (DST), Central Road Research Institute, (CRRI), Central Building Research Institute (CBRI), Geological Survey of India (GSI), the Indian Institutes of Technology (IITs), and University of Roorkee. The now and Avalanche Study Establishment (SASE) of the Defence Research & Development Organization (DRDO) specializes in the studies of snow avalanches. These institutes have prepared zonation maps by integrating multiple data bases such as topographical data, geological data, remote sensing data, geo-technical investigation data, climatological data and actual occurrence data. Hazard zonation mapping based on this technique of integrated multiple database is used for forecasting and forewarning.

Strict enforcement of existing rules and framing of new rules to stop indiscriminate quarrying and mining near vulnerable slopes and to stop deforestation in high risk areas will go a long way to reduce the hazards due to landslides and snow avalanches. The houses and roads in the vulnerable zones should be built only according to the prescribed building codes which need to be enforced strictly.

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