Himalayas, as a region, have always been susceptible to disaster, due to the neo-tectonic mountain-building process, like earthquakes, landslides, floods, etc. The spread of reckless developmental activities has transformed many natural disasters into man-made events. Such calamities play a grave negative socio-economic role on the national economy and exert additional pressure on an already strained national economy.

 

 

It is important to discuss the origin of the Himalayan Mountains for understanding the natural seismicity in the Himalayas. Around 45 million years (during the Eocene period on Geological Time Scale), India collided with Eurasia. This was due to the continued northward migration of India. Since then, India has penetrated some 2000 km into Asia leading to the creation of Himalayan Mountain Range and this process is still in continuation. In this process, the Himalayan plate is undergoing beneath the Eurasian plate.

 

Thus, the Himalayan Mountains are the only ‘living’ mountains in the world as the plate tectonic activities churning within the Himalayas are leading to increase in its height. This internal turbulence within the Himalayas is solely responsible for their active seismic nature as corroborated by a large number of earthquakes traversing the entire belt from time to time, taking a heavy toll of life and property. Overall, more than ninety percent of the earthquakes occurring in India fall within the Himalayan mountain zone and its foothills. Scientifically, it has been experimentally shown that the seismicity creeps in an area through pre-existing zones of weakness and the neo-tectonic activities of Himalayas make it a zone of weakness. In last ten years, two major earthquakes have occurred in Uttaranchal namely the Uttarkashi earthquake (1991) and the Chamoli earthquake (1999).

It should be noted that the damages in the event of an earthquake primarily result from the unplanned developmental activities in seismicity-prone areas, which increase the casualties of life and loss of property manifold. Therefore special attention should be paid in undertaking major developmental activities like human settlements, urbanization, road building, laying of railway tracks etc. Japan, seismically one of the most vulnerable countries, has successfully shown that the damages accruing from an earthquake, even with a higher magnitude of 7 on Richter Scale, can be minimized by adopting an integrated approach of generating awareness, building earthquake resistant structures, always keeping the level of preparedness at a higher level, and preparing and regular updating of elaborate disaster management plan in case of an eventuality.

 

 

Landslides are defined as the mass movement of rocks, debris or earth down a slope dislodging earthen material on its way. Often they are associated with other calamities like earthquake, floods or volcanoes, involving movement of earth. Prolonged rainfall also causes heavy landslides, especially in mountain areas devoid of vegetation cover, blocking the flow of river. These river blocks, if and when they burst, can cause havoc to the settlements downstream. Landslides are common occurrence in the hilly states of India (Table 1.2). For example, 380 people were killed when massive landslides washed away the whole village Malpa, Uttaranchal (then Uttar Pradesh) in 1998. This year (2003) a number of landslides occurred during the monsoon season, triggered by the heavy rains. This led to the blockade of roads in most parts of the state, like, Shimla-Kalka road (Himachal-Haryana link road), the Hindustan Tibet Highway,and other similar events. Incidents of landslides were also reported from Solan, Sirmaur, Bilaspur, Hamirpur and Palampur.

 

 

Cloudbursts are sudden heavy rainstorm and its downpour. Generally, when clouds traversing pass over an area of low atmospheric pressure and temperature, vapours are condensed into raindrops, which fell on the ground by virtue of their weight. However, in mountains areas clouds are multi-layered. When one layer traversing at higher altitude enter into a zone of extremely low atmospheric pressure, then suddenly all the vapours are converted into water simultaneously. This water-column, while falling from the height, also takes the water from the clouds of other lower layers and rapidly falls on the earth. This is called cloudburst.
   
Most of the cloudbursts incidents take place in the Himalayan Mountains and only a few have been recorded in Extra Peninsular India. Since the major rainstorm zones have already been identified and demarcated on a national scale, there should be no reason that people continue to suffer from it. It underscores the inadequacy of our efforts in disaster mitigation.

One major recent cloudburst event occurred in Himachal Pradesh on 16 August 2003 at 2.30am at Pulia Nala, Kullu district, killing 50 labourers working at an NHPC site. Another major event occurred on the night of August 10, 2002 in Budha Kedar, Balganga Valley, Tehri, and Ratnali in Uttar Kashi, both in Uttaranchal. It led to widespread destruction in 23 villages of Balganga Valley and out of these 4 villages (namely, Marwari, Meddh, Agunda and Kot) were completely devastated. 19 persons died in these four villages. In remaining 19 villages (namely, Agar, Koti, Ragasya, Titrona, Niwalgaon, Toli, Pinswad, Urni, Genwali, Jakhna, Bhigun, Thati, Bisan, Bhaladgaon, Gomphal, Chani, Padokhan, Sirsot and Sem) though there was no casualty but all suffered from landslides, land subsidence and cracks in houses.

 

 

The youngest mountain ranges of the Himalayas have been assessed as the most vulnerable stretches of world with regard to forest fires. In 1999, forest-fires in the hills of Uttaranchal destroyed more than 3,75,000 hectares of forest. The same year, more than 450 cases of forest fire were reported in Himachal Pradesh and by May 1999, more than 80,000 hectares of forests were turned to ashes.
Factors leading to a forest fire can be broadly grouped in three major categories, though in reality, a big forest fire outbreak is caused from the fractional contribution of many of these factors.

 

 

Floods are caused by extra-ordinary intensive rainfall of longer duration. Every year, floods are recorded in one part of the country or the other. The major flood-prone areas of the country are already identified, yet there is a paucity of planned systematic strategy dealing with the floods. This lack has resulted in massive damages in the last 50 years. This also reflects a failure at the policy level.

 

In the Himalayan region, flash flood is one of the major disaster which causes heavy damage to human lives, livestocks and property.