User talk:Chanduchary009

DISASTERS

DISASTERS:-

A disaster is a serious disruption, occurring over a relatively short time, of the functioning of a community or a society involving widespread human, material, economic or environmental loss and impacts, which exceeds the ability of the affected community or society to cope using its own resources.

In contemporary academia, disasters are seen as the consequence of inappropriately managed risk. These risks are the product of a combination of both hazards and vulnerability. Hazards that strike in areas with low vulnerability will never become disasters, as in the case of uninhabited regions.

Developing countries suffer the greatest costs when a disaster hits – more than 95 percent of all deaths caused by hazards occur in developing countries, and losses due to natural hazards are 20 times greater (as a percentage of GDP) in developing countries than in industrialized countries.

Nature and Management:

A natural disaster is unforeseen, severe and immediate. Pollution, ozone depletion in the stratosphere and global warming come in this category. Natural disasters include cyclones, earthquakes, floods, drought (though these two are now being increasingly considered ‘man- made’ disasters) heat and cold waves, landslides, avalanches, flash floods, severe thunder­storms, hail, low level wind shears, and microburst. The destructive potential of any natural hazard is estimated basically by its spatial extent and severity. Spatial extent upto which the effect of a disastrous event could be felt may easily be classified into small, medium and large scales. The phenomenon extending from a few kilometers to a few tens of kilometers are termed as small scale.

Growing industrialisation and unjustified exploitation of natural resources have brought our echo system to a verge of non-reversibility and imbalance. This has led to a threat from a set of natural hazards like pollution, global warming and ozone depletion on large or global scale. In some phenomena, such as cyclones, flood, etc. the time available to respond to the hazard is of the order of a few days. Hence early warning, communication, and rescue operations are possible. But, in a few cases like flash floods, microburst, etc., the response time is of the order of few minutes only, which calls for a very fast early warning and efficient communication system.

The human-activity-induced hazards like pollution and global warming have already started showing their precur­sors, giving sufficient time to control and avoid these hazards by long term planning. On the contrary, in earthquakes no proven methods has yet been evolved to give any prior warning and so post-hazard mitigation is the only alternative.

Role of Communication For a developing country like India, the role of communication in disaster mitigation is extremely critical. Vast areas of the country do not have telephone/ telegraph links. These can neither be provided in a short span of time available for mitigation nor are there resources to do so.

We have to depend on existing links, many of which completely break down during the disaster. The various types available for dissemination of disaster warning as well as arranging mitigation are: (a) land line links; (b) underground cable links; (c) wireless links; (d) microwave (LOS); and (e) satellite links. The only effective communication which is likely to remain completely or partially unaf­fected is the satellite link. Earthquake:

Stated simply, ‘an earthquake is a vehement shake of the earth from natural causes’. Technically an earthquake is a phenomenon of strong vibrations occurring on the ground, consequent to release of large amount of energy within a short period of time because of some disturbance in the earth’s crust or in the upper part of the mantle. Causes:

The theory of plate tectonics offers a comprehensive explanation for several geological phenomena — continental drift, mountain building and volcanism, and, of course, earthquake. According to this theory, when the molten mass that was the earth billions of years ago cooled down, the crust that was formed was not one homogenous piece but broken into about a dozen large plates and several smaller ones with their thickness ranging from 30 km down to the lithosphere at depth of about 100 km or so. Cyclones:

Tropical cyclones, the most destructive of nature’s phenomena, are known to form over all tropical oceans except over the South Atlantic and the South Pacific, east of about 140° W. An intense low pressure area in the atmosphere is formed before/after the monsoon. It is associated with fierce wind and heavy rainfall. Horizontally it extends from 500 to 1000 km and vertically from the surface to about 14 km.

Severe tropical cyclones cause considerable damage to property and agricultural crops. The principal dangers posed are: (a) fierce winds; (b) torrential rains and associated flooding; and (c) high storm tides (combined effect of storm surge and tides). Rainfall up to 20 to 30 cm a day is common.

The highest ever sustained winds recorded in the case of tropical cyclones are 317 kmph. Storm surge (rise of sea level) of four metres are common. The highest sea level elevation in the world due to continued effect of storm surge and astronomical high tide occurred in 1876 near Bakerganj, where the sea level rose by about 12 metres above the mean sea level on that occasion.