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“Disaster is an undesirable occurrence resulting from forces that are largely outside human control, strikes quickly with little or no warning, which causes or threatens serious disruption of life and property including death and injury to a large number of people, and requires therefore, mobilisation of efforts in excess of that which are normally provided by statutory emergency services”.
Landslide is a form of mass movement in which rock and debris move rapidly downslope under the influence of gravity as a result of failure along a shear plane.
Consequences:
i. Diversion of river courses due to landslides can also lead to flood and loss of life and property.
ii. It also makes spatial interaction difficult, risky as well as a costly affair, which, in turn, adversely affects the developmental activities in these areas.
The Disaster Management Bill, 2005, defines disaster as a catastrophe, mishap, calamity or grave occurrence affecting any area, arising from natural or man-made causes, or by accident or negligence which results in substantial loss of life or human suffering or damage to, and destruction of, environment, and is of such nature or magnitude as to be beyond the coping capacity of the community of the affected area.
There are three stages involved in disaster mitigation and management:
The initial conditions for the emergence of a tropical cyclone are:
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In central and western India, the droughts are more frequent because of the following reasons:
1. The monsoons do not occur in these areas frequently.
2. The rainfall is about 75 cm per annum.
3. The intensity of monsoon winds becomes weak as they reach in these areas.
The basic requirements for the formation of cyclone are as mentioned:
1. Large and continuous supply of warm and moist air.
2. Strong Coriolis force.
3. Unstable condition through the troposphere that creates local disturbances around which a cyclone develops.
4. Absence of strong vertical wind wedge.
(i) Temperature of the oceanic surface over 26°C.
(ii) Appearance of a closed isobar.
(iii) Low pressure dropping below 1000 mb.
(iv) Areas of circular movement first spreading to a radius of 30-50 km then increasing gradually to 100-200 km and even to 1000 km.
(v) Vertically the wind speed first rising to a height of 6 km then much higher.
The zone are:
(i) Very high damage risk zone
(ii) High damage risk zone
(iii) Moderate damage risk zone
(iv) Low damage risk zone
(v) Very low damage risk zone.
(ii) Aridity and drought: Drought can occur in any area regardless of the amount of rainfall the area may receive. It can occur in small pockets or over a large area. Aridity is a permanent condition whereas drought is a temporary situation.
Mass wasting: Natural removal of soil and rock from slopes is known as mass wasting.
Intensity: The intensity is the measure of the damage caused by the earthquake and is measured on Mercalli Scale.
Disasters are caused also by some human activities. Some activities carried out by human beings are directly responsible for man-made disasters. These are development activities which become the causes of disasters, sometimes. Example :
1. Bhopal gas tragedy.
2. Chernobyl nuclear disaster and wars.
3. Release of CFCs and increase of greenhouse gases.
There are some other activities of human beings that accelerate or intensify disasters indirectly. Landslides and floods are due to deforestation, unscientific land use and construction activities in fragile areas.
The landslide-prone regions are:
Structure of tropical cyclone:
i. Tropical cyclones are characterised by large pressure gradients.
ii. The centre of the cyclone is mostly a warm and low-pressure, cloudless core known as eye of the storm.
iii. Generally, the isobars are closely placed to each other showing high-pressure gradients.
iv. Normally, it varies between 14-17mb/100 km, but sometimes it can be as high as 60mb/100km.
v. Expansion of the wind belt is about 10-150 km from the centre.
Vulnerability is the potential for loss or the extent to which an individual, community or place can be affected because of a disaster.
India can be divided into natural disaster vulnerability zones based on droughts as under:
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Sometimes a mass of earth saturated with water slides down a hill slope causing landslides. There are many varieties of landslides depending on the mass, sliding and the distance traversed by it. Those which move only through short distances are called slumps. When millions of cubic of material moves through thousands of feet distance, they are known as rock slides. When under gravity rock material falls down a high cliff, debris fall or rockfall occurs.
Effects of landslides : Landslides produce great scars on the sides of mountains, and sometimes give a rippled shape to the hillside on account of mixed rock slumps on the back slope. Landslides and rockslides are of frequent occurrence in many mountains. In 1957, such a huge landslide came down in Kashmir. The traffic was suspended for many days. Recently a landslide in Tehri-Garhwal region occurred due to cloud burst.
A.
AtmosphericThe resolution of the World Conference on Natural Disasters Reduction is as mentioned below:
(i) It will note that each country has the sovereign responsibility to protect its citizens from natural disasters;
(ii) It will give priority attention to the developing countries, particularly the least developed, land-locked countries and small-island developing states;
(iii) It will develop and strengthen national capacities and capabilities and, where appropriate, national legislation for natural and other disaster prevention, mitigation and preparedness, including the mobilisation of non-governmental organisations and participation of local communities;
(iv) It will promote and strengthen sub-regional, regional and international cooperation in activities to prevent, reduce and mitigate natural and other disasters, with particular emphasis on:
(a) human and institutional capacity-building and strengthening;
(b) technology sharing: the collection, the dissemination and utilisation of information; and
(c) mobilisation of resources.
The spatio -temporal Distribution of tropical cyclone in India:
India can be divided into the following five earthquake zones :
(i) Very high damage risk zone
(ii) High damage risk zone
(iii) Moderate damage risk zone
(iv) Low damage risk zone
(v) Very low damage risk zone.
Effects of Earthquakes : Earthquakes have all encompassing disastrous effects on the area of their occurrence. Some of the important ones are :
Effects of Earthquakes
|
On Ground |
On man-ade structures |
On Water |
|
Fissures |
Cracking |
Waves Possible chain effects |
Apart from these, the earthquakes also have some serious and far reaching environmental consequences. Surface waves produce fissures on the earth's surface. Earthquakes are responsible for landslides and often these cause obstructions in the flow of rivers and channels resulting in the formation of reservoirs.
Earthquake Hazard Mitigation : It is not possible to prevent the occurrence of earthquakes. The next best option is to emphasize on disaster preparedness and management rather than curative measures such as :
(i) Establishing earthquake monitoring centres (seismological centres) for regular monitoring and fast dissemination of information among the people in the vulnerable areas. Use of Geographical Positioning Systems (GPS) can be of greater help in monitoring the movement of tectonic plates.
(ii) Preparing a vulnerability map of the country and dissemination of vulnerability risk information among the people and educating them about the ways and means to minimise the adverse impacts of the disasters.
(iii) Modifying the house types and buildings-designs in the vulnerable areas and discouraging construction of multi-storey buildings, large industrial establishments and big urban centres in such areas.
(iv) Finally, making it mandatory to adopt earthquake-resistant design and use light material in major construction activities in the vulnerable areas.
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