Prevention and Mitigation of Avalanche Disasters in Western Himalayan Region

Transcription

1 Natural Hazards 31: , Kluwer Academic Publishers. Printed in the Netherlands. 357 Prevention and Mitigation of Avalanche Disasters in Western Himalayan Region A. GANJU and A. P. DIMRI RDC-SASE, HIM PARISAR, Plot No #01, Sectore #37A, Chandigarh , India (Received: 3 April 2002; accepted: 25 October 2002) Abstract. An avalanche is a result of the structural collapse of the snow cover in the upper reaches of mountain slopes in the snowbound belt. They take a heavy toll, year after year and property worth millions is destroyed. Besides loss of lives, the avalanches also destroy forest and disrupt road communication, thereby hindering the hill area development and affecting the defense of the nation. This paper discusses the cause of avalanches, the magnitude of their destruction power and the techniques followed in India by the Snow and Avalanche Study Establishment (SASE), a DRDO Laboratory, for mitigating avalanche disasters in Western Himalayan Region for the defense forces. The authors suggest that an integrated plan for mitigating the avalanche disasters should be set up at national level, involving defense forces and state governments. 1. Introduction Snow avalanche (Figure 1) is a relatively unknown natural hazard, due to the remoteness of the scene of the disaster, away in the mountains. Avalanches, however, have rocked mountains and claimed a toll of lives and property, winter after winter. Both European and Indian History is replete with tragic accounts of avalanche destruction. A few of the great avalanche disasters that killed thousands of people are: The Great Glaruish avalanche disaster of Switzerland. Alexander the Great s crossing of the mountains of Persia, Hindukush and Chowkpass. Napoleons s crossing of the Great St. Bernard Pass in May Hannibal s army in 218 BC, while crossing the Alps, lost about 18,000 men, 2,000 horses and several elephants. Although avalanches in Himalaya reach stupendous proportions and are vicious in their frequency, they have, until recently proved less disastrous, mainly due to their limited interaction with man and his artefacts. The earliest recorded avalanche accident in Himalaya dates back to 1838, when a village near Trilokinath temple in Lahaul district of Himachal Pradesh (HP) was completely swept away, killing about 60 people and 3,000 head of cattle, Mohan Rao et al. (1988). March 1979 witnessed all-round avalanche activity, claiming over 300 lives, several hundred

2 358 A. GANJU AND A. P. DIMRI Figure 1. A flowing avalanche of tremendous destructive potential. head of cattle and destroying millions of rupees worth of property in the States of Himachal Pradesh and Jammu Kashmir (J&K) (Figure 2). In November 1986, an early snowfall event triggered a few avalanches and blocked a large convoy of vehicles. This was followed by a severe blizzard, which claimed over a hundred lives and damaged a great deal of property. An unprecedented snowfall in March 1988 led to a major avalanche disaster in an area of J&K, claiming over 200 lives and causing considerable damage to property. Avalanches have also affected the settlements around the shrines of Sri Badrinath Puri and Sri Kedarnath in Uttaranchal. Data collected over the last three decades (Figures 3, 4

3 PREVENTION AND MITIGATION OF AVALANCHE DISASTERS 359 Figure 2. Destruction caused by March 1979 avalanche in Lahaul and Spiti Valley (HP). Half of the Guiskar village was totally wiped away by the avalanche. and 5) indicate that on an average lives and property worth a few millions are lost every year in avalanches. Actual figures are likely to be many times higher since a number of incidents go unreported. 2. Hazard Potential of Avalanches Avalanches, though known for their destructive potential, have not been considered a major natural threat to lives and property because on an absolute scale the death and destruction figures are not very alarming. The avalanche activity in the Western Himalayan region becomes vicious from January to March. Climax avalanches take a heavy toll. Generally, winters with heavy snowfall are associated with major avalanche winters, but severe avalanche activity has also been known to occur during winters with less snowfall, depending on how the snowpack evolves on mountain slopes. Sixty-eighty percent of avalanches in Himalaya occur with every major snowstorm. Thus they are categorized in the frequent category and are generally predictable. However, the remaining 32 percent (less predictable) trigger as delayed-action avalanches and are very destructive. The avalanche debris on roads/tracks accumulates to about 5 20 m in height, thus affecting about 40 percent of total snow bound road length in the Western Himalaya (Figure 6). The avalanche area of India lies along the northern part of our country, covering Jammu and Kashmir, Himachal Pradesh and the hills of Uttaranchal, extending up to Sikkim in the eastern region. The problem, however, is more acute in the western part of the Himalaya where there is frequent interaction of troops and civilians with avalanches.

4 360 A. GANJU AND A. P. DIMRI Figure 3. Annual fatalities due to avalanche accidents in the Himalayas. On average about persons get killed due to avalanches every year in the western Himalayan region.

5 PREVENTION AND MITIGATION OF AVALANCHE DISASTERS 361 Figure 4. Damage as a result of loss of cattle due to avalanche in the western Himalayas. Figure 5. Damage due to destruction of buildings, bridges and vehicles in avalanche (1929 to 1990). 3. Magnitude of Problem Snow avalanche is a sudden downward motion of snow mass on a slope. It may bring ice, soil, forest and rocks along with it. Snow avalanches can attain speeds up to 200 km/h and exert pressure up to 50 T/m 2 (Figure 7). Such speed and the pressure are bound to cause soil erosion in soil terrain and forest destruction in a forested area in the first instance. Besides that, there are a number of problems

6 362 A. GANJU AND A. P. DIMRI Figure 6. Avalanche affects 40 percent of various road axes in the western Himalayan region. associated with avalanches that affect mountain people, directly or indirectly. Life in the mountains becomes totally paralyzed, thus affecting the overall wellbeing of mountain people. Due to the disruption of traffic, essential supplies to the interior in snowbound areas is affected. Loss of forest cover and soil cover, in addition to road damage, impedes the hill development schemes. While on the one hand, the avalanche debris dams rivers causing flooding, the same avalanche debris on the ground locks up the water required during the spring period. Avalanches affect military operations as well as border area security and safety. The avalanche-prone states are Jammu and Kashmir, Himachal Pradesh, Uttaranchal and to certain extent Sikkim. In total, 109 villages in HP, 91 in J&K and 16 in UP are affected due to constant threat of avalanches throughout the winter season (Figures 8, 9 and 10). Out of seven road axes in J&K (including laterals), only two permit some pedestrian traffic during winter months and only one road axis allows moving vehicular traffic. The other four axes remain more or less cut off for four to five months. Similarly, both the snowbound road axes, that is, Manali Leh and Hindustan Tibet road in Himachal Pradesh remain cut off for five to six months of the year. Taking into consideration the present state of affairs and the future view, the avalanche threat is likely to assume greater proportions in the near future. Uncontrolled felling of trees, a population explosion (resulting in more and more people seeking refuge in the hills) are only two aspects that signal the greater interaction of avalanches. Besides that, the socio-economic development of mountain regions, increasing interest in winter sports, and adventure activities, would definitely increase the risk level. And finally, in the absence of a general awareness of safety

7 PREVENTION AND MITIGATION OF AVALANCHE DISASTERS 363 Figure 7. Maximum speed and thrust exerted by an avalanche (Courtesy McClung). Figure 8. Number of villages affected in comparison to number of avalanches in Jammu and Kashmir. and rescue methods among backcountry travelers, the threat is likely to pose serious problems in future. 4. Avalanche Hazard Mitigation Avalanche is a recurring phenomenon. Complete control of avalanches is possible only through active methods comprising essentially the erection of structures, af-

8 364 A. GANJU AND A. P. DIMRI Figure 9. Number of villages affected in comparison to number of avalanches in Himachal Pradesh. Figure 10. Number of villages affected in comparison to number of avalanches in Uttaranchal. forestation and artificial triggering methods. Structural control and afforestation methods, besides being costly, are also very difficult to implement. In some places these methods cannot be implemented at all because of the logistic problems. In any case, cost effectiveness versus facility to be protected needs to be weighed properly before implementation of any of the active methods for the control of avalanches. While methods like structural control or afforestation arrests the creep and glide motion of snow on slopes, and thus avalanches too, artificial triggering helps to bring down the avalanches before they reach stupendous proportions. The latter method is relatively cheap.

9 PREVENTION AND MITIGATION OF AVALANCHE DISASTERS 365 Figure 11. A typical avalanche hazard map of a road axis in Jammu and Kashmir PASSIVE METHODS The passive methods include: Awareness; Forecasting; Safety and Rescue Awareness There is a general unawareness among backcountry travelers (remote villages) about the avalanche phenomenon and the necessary safety and rescue measures. A study conducted in HP during the early eighties revealed that people preferred to stay indoors all through the winter rather than to move about with precaution. A few deliberate movements, whenever made, were never made with the proper precautionary measures. The general awareness of the affected population can be increased through the following steps: Preparation and Publication of Hazard Map. This map should include information on all types of hazards besides avalanches. Such maps have been published by Mountain Research Station, Institute of Arctic and Alpine Research, University of Colorado, Boulder, USA. The map has to be drawn on a small scale so that the users can identify their areas of interest distinctly with associated natural hazards. A sample map showing the potential threat of avalanches along a roadside is shown in Figure Preparation and Publication of Avalanche Atlas. This atlas provides the complete information on avalanche sites. Their location, frequency, ground conditions, past history and user notes on safety and rescue would be of immense

10 366 A. GANJU AND A. P. DIMRI help in curbing avalanche casualties. SASE has already published six such atlases of different road axes in J&K and HP states. Examples are the Avalanche Atlas Chowkibal-Tangdhar Axis (1995); Snow and Avalanche Study Establishment publication Training. Training in avalanche safety and rescue methods would go a long way to bring down the avalanche casualties. The efforts put in by SASE in training army personnel in safety and rescue methods can from time to time be extended to the civil population. A selected group of people chosen from various villages can be given training at training institutes. They would in turn train people at village level Publicity through Media. Telecasting of regular programmes of public interest on avalanches, safety and rescue methods, avalanche news in a pre-informed time slot would increase the awareness level among users. A detailed description of avalanche paths, safe routes, previous history etc. of avalanches on different routes in different states would help if telecast on TV AVALANCHE FORECASTING Mitigation through avalanche forecasting is by far the best and the cheapest method available. However, the methodology suffers from objectivity and above all requires memorizing of antecedent conditions, and is thus subject to continuous revisions. The methodology involves integration of current hazard with projected weather conditions. It has the advantage of covering larger areas. Further improvement can be achieved by enlarging the observatory network and by the development of forecasting models for Western Himalaya. The present forecasting accuracy of between percent would improve considerably with the improvement in the observatory network and development of avalanche forecasting models. The current hazard of potential avalanche sites is found by digging a pit in the snow cover and determining its structure. However, it is not feasible to do this exercise at all the avalanche sites because of the problem of accessibility. For different sites current snow pack stability is assessed through extrapolation of observatory data and pit information data collected at the observatory site. Indirectly, the current stability of the snowpack is assessed by following the Snowcover Build up approach. This technique requires building up of snow cover from day one using easily measurable meteorological parameters and snow amount. This qualitative analysis, though helpful, is again highly subjective. Quantitative assessment of snow pack stability is achieved by modeling snow cover. This has been done at SASE and the output of the simulated snow cover profile is shown in Figure 12. This model and other models like Digital Terrain Model (DTM), Constitutive Model, Stress Distribution Model (SDM) and finally the Failure Criterion

11 PREVENTION AND MITIGATION OF AVALANCHE DISASTERS 367 Figure 12. Snowcover simulation model provides information on the complete snowpack structure. Model, would provide complete information of the current status of snow pack stability. The other approach is to use statistical tools to predict avalanches. For effective functioning of these models, a dense network of Automatic Weather Stations (AWS) is required. SASE s manned observatories are sparse. Moreover, data transmission by radio (HF) has its own associated problems. The efforts of SASE in installing 16 Automatic Weather Stations requires further support from user agencies to enlarge the network of Automatic Weather Stations. There is a requirement for a unified National Scheme, which would involve all user agencies to undertake this project. In terms of projected weather, five parameters are important. While a fair approximation of temperature and radiation parameters can be made, other parameters like precipitation, wind and relative humidity have to be assessed through some forecast model. Presently projected weather estimates are made qualitatively by analyzing INSAT, NOAA and METEOR imageries and synoptic charts of IMD. A Quantitative Precipitation Forecast (QPF) Model needs to be developed and SASE has already initiated a research effort in this direction Safety and Rescue Methods Safety in terms of preparedness in clothing, equipment, safe route, projected weather, physical fitness etc. is basic for any back country traveler to be prepared

12 368 A. GANJU AND A. P. DIMRI for negotiating an avalanche-prone area. For people staying in avalanche-prone areas in the Western Himalayan region, the safety measures mean only confining themselves indoors during winter months. In certain areas, avoiding steep slopes and moving during early morning hours after about 48 to 72 hr after the cessation of a storm has been the other option used to avoid the risks. The do s and don ts of crossing an avalanche path should be known and the actions to be followed on being hit by an avalanche should be well rehearsed in advance. Some of the important do s and don ts are given as follows: Cross-slopes one at a time. Do not move in clusters. Assess the stability of avalanche slopes before crossing them by using stability tests or by artificial triggering of avalanches. Place an avalanche observer on each side of the avalanche. All persons crossing an avalanche slope must tie an avalanche cord to their waist and trail the remaining length behind them. Always carry an avalanche rod and an avalanche cord, one per person. Carry Avalanche Victim Detector (AVD) at the scale of one per person while crossing an avalanche-prone slope. Always remain in communication with the Base Station in order to receive timely rescue in case of an accident. Adhere to avalanche warnings issued by SASE. Even with all preparedness, avalanches may claim lives year after year. This calls for efficient rescue operations because speed is of the essence in any rescue work. In case of an avalanche victim, it becomes even more important because survival chances reduce by 50 percent in the first 30 minutes. Immediate responsibility for rescue thus falls on the survivors. Besides attempting to rescue the buried victims, they should simultaneously try to inform the rescue organizations, which thus demands an efficient communication system (Ganju et al., 1989). An organized rescue with proper equipment and organization is essential in locating buried avalanche victims. Adequate information pertaining to these aspects is available in various books and papers. Service personnel are being trained on all of these aspects. However, it has not yet trickled to civil populations in snow-bound, avalanche-prone areas. Sufficient literature in the form of handouts, users guide, posters has been prepared at SASE to generate awareness. They should be made use of by the State Administration to save precious lives in avalanche-prone areas. Organized rescue organizations are non-existent in India. This is a must and to make these organizations most effective, they should come under the banner of some kind of national scheme for the management of national hazards (Ganju et al., 1989). These rescue organizations in peacetime should assist travelers, expeditions, mountaineers etc. and impart training to the people down to the village level. The responsibility for efficient functioning of these organizations should be entrusted

13 PREVENTION AND MITIGATION OF AVALANCHE DISASTERS 369 to the State Governments which in turn must identify areas where such rescue organizations are to be located. Needless to say, all rescue organizations must be well equipped and well versed with the local terrain so as to use it to the best advantage ACTIVE METHODS Active methods include the following: Structural Control; Afforestation; Artificial Triggering Structural Control Structural control of avalanches is a positive method and provides 100 percent protection from avalanche danger. There are different types of structures, which, depending on the cost-effectiveness and types of terrain, are placed in the different zones of an avalanche. The starting zone (where an avalanche starts) is called the Formation Zone. The track region (where avalanche flow accelerates) is called the Middle Zone. The bottom portion (where avalanche flow decelerates) is called the Run Out Zone. These structures either guide avalanches away from the facility to be protected or prevent the avalanche from initiating. the different types of structures used are described in the following paragraphs Formation Zone Control Snow Bridges: horizontal steel members placed at near-right-angle to avalanche slope. They arrest the initiation of crack and fracture in snowpack on a mountain slope. Snow Rakes: vertical steel members placed at near-right-angle to avalanche slope. They also arrest the initiation of crack and fracture in snowpack on a mountain slope. Snow Nets: steel wire rope nets hung on poles and anchored at the base to arrest fracture initiation in snowpack on a mountain slope Middle Zone Control Diversion Dam: diverts the flow of avalanche snow in different direction to protect some facility in the path of avalanche. Snow Gallery: protects a road or any facility in the path of an avalanche by allowing flowing mass to go over its roof. Wedge: divides the flowing mass in two directions to protect the facility directly below the wedge.

14 370 A. GANJU AND A. P. DIMRI Run Out Zone Control Mounds: arrest and break the momentum of the decelerating avalanche mass to stop in short distance. Thereby protect the facility in the far end of the Run Out Zone of avalanche slope. Catch Dam: holds the flowing avalanche mass in a large depression made in thepathofanavalanche Afforestation Forests arrest the flow of avalanches in a number of ways. A forest with thick growth of high trees in the starting zone inhibits the formation of avalanches for the following reasons (Sethi, 1989). Tree trunks support the snow cover and provide an anchor to potential slab avalanches. Snow drifting is almost eliminated. Tree canopy retains snow and releases it gradually. Forest canopy moderates variability in the net energy exchange with the snow surface, which tends to produce a uniform snow temperature distribution and stable snow cover. In India the timberline rises to a maximum of 3,500 m. About 50 percent of avalanche sites in Pir Panjal have formation zone altitudes below 3,000 m. Similarly, about 31 percent of avalanche sites in Great Himalaya have formation zone altitudes below 3,000 m. All avalanche sites in Karakoram have their formation zone altitudes above 3,000 m. Furthermore, tree line is confined to certain pockets only near water bodies. Afforestation can be taken up at all sites where formation zone altitudes of avalanche sites are below 3,000 m and thus mitigate the avalanche danger. The only drawback with afforestation is that saplings cannot sustain creep and glide forces of snow and die in the very first winter. Afforestation in conjunction with structural control is good, provided sufficient wood is available for erecting structures. This method, though most effective, is expensive Artificial Triggering This method attempts to pre-empt the release of avalanche by infantry weapons before it triggers naturally. This method inhibits the disastrous build up of snow cover on slopes. The method is generally adopted in conjunction with avalanche forecasting because unless a snow pack on a mountain slope is unstable, no amount of weapons fire would get it down. Artificial triggering of avalanches is an extension of avalanche forecasting (Agrawal, 1990). 5. Conclusion Avalanche hazard has already assumed dimensions comparable with other natural hazards and is likely to grow in the near future. Thus there is a necessity to generate

15 PREVENTION AND MITIGATION OF AVALANCHE DISASTERS 371 greater awareness among backcountry travelers. There is also a requirement for improving the accuracy of avalanche forecasting by developing avalanche-forecasting models for different areas. If models are to produce accurate results, there is a need to enlarge the observatory network (Automatic Weather Station based). For projected weather conditions there is a requirement to develop a Quantitative Precipitation Forecast (QPF) model. And finally, there should be some national policy for creating well equipped and trained Avalanche Safety and Rescue Organizations down to village level. Acknowledgement The authors are grateful to Maj. Gen. SS Sharma, KC, VSM for his encouragement and the Scientists and Scientific Assistants of Avalanche Forecasting Centre, HQ SASE for assistance in compiling the information provided in this paper. References Agrawal, K. C.: 1990, Artificial Triggering of Avalanches, SASE Publication. Fraser, Colin: 1966, Avalanche Enigma, pp Ganju, A. and Prashar, D. K.: 1989, Movement in avalanche prone areas safety and rescue, Symposium on Preparedness, Mitigation and Management of Natural Disasters, Vol. 1, pp Rao, Mohan et al.: 1988, Impact of avalanche problems in some of the hill areas of Himachal Pradesh (1988), National Seminar on Hill Area Development, Jun 1988 Shimla (HP). Sethi, D. N.: 1989, Structural control of avalanches to mitigate avalanche danger, Symposium on Preparedness, Mitigation and Management of Natural Disasters, Vol.1.

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