Environmental Hazards: Classification of Environmental Hazards and Disasters!
Meaning and Concept of Disaster:
Environmental hazards may be defined as those extreme events either natural or anthropogenic which exceed the tolerable magnitude within or beyond certain time limits, make adjustment difficult, resulting catastrophic losses of property, income and lives and become head lines of different news media at world level.
ADVERTISEMENTS:
The term environmental hazard may be distinguished from environmental disaster as follows. Hazards are the processes which cause an accident or extreme event or danger where as disaster is a sudden adverse or unfortunate extreme event which causes great damage to human beings as well as plants and animals, i.e., disasters occur rapidly, instianeously and indiscriminately. Thus, environmental hazards are the processes where as environmental disasters are the results or responses of environmental hazards.
Classification of Environmental Hazards and Disasters:
On the basis of main causative factors, the environmental hazards and disaster are of two types:
(1) Natural hazards and disaster and
(2) Anthropogenic hazards and disaster.
ADVERTISEMENTS:
Natural hazards are further subdivided into two categories:
(i) Planetary hazards and
(ii) Extraplanetary hazards and disasters.
Planetary hazards and disasters are of two types:
ADVERTISEMENTS:
(α) Terrestrial or endogenous hazards, (volcanic eruption, Earthquake) and (β) Atmospheric or exogeneous hazard (Cyclone, Flood, drought) Anthropogenic hazards and disasters are of three types:
(i) Physical hazards (land slides, soil erosion, Earthquakes)
(ii) Chemical hazards and disasters (sudden out break of lethal poisonous gases from industries, nuclear explosion, leakage of radioactive elements,
(iii) Biological hazards and disaster (sudden rise in population of species in a given habited).
(A) Earthquake and its management:
ADVERTISEMENTS:
An earthquake is a sudden motion of the ground surface, ranging from a faint tremor to a wild motion capable of shaking buildings apart and causing gaping fissures to open in the ground. It is caused by an abrupt release of slowly accumulating stress.
In other words, earthquake is a form of energy of wave motion transmitted through the surface layer of the earth in widening circles from a point of sudden release the focus. The intensity of energy released by an earthquake is measured by the Richter scale, after the name of the scientist C.F. Richter (1935). Although the scale range between 0 and 9, it has no upper limit of number because it is a logarithmic scale. Another scale of the measurement of intensity of earthquakes is mercalli scale.
The intensity of earthquake depends on a variety of factors e.g. magnitude, distance from the epicenter, acceleration, duration, amplitude of wave, type of surface, water table, nature of the geometrical of the concerned region and nature and type of constructions. A comparison in between Mercalli intensity and Richter magnitude scale and corresponding effects is shown in table 11.2.
Earthquakes are caused due to disequilibrium in any part of the crust of the earth. The disequilibrium is due to volcanic eruption, faulting and folding, up warping and down warping, hydrostatic pressure of manmade water bodies like reservoirs and lakes, and plate movement Recently, Plate tectonic theory has been suggested to explain the occurrence of earthquake.
According to this theory, earth is composed of solid and moving plates having either continental, crust or oceanic crust or both, the earth’s crust is consisted of six major plates (Eurasian plate, Indian plate, American plate, African plate. Pacific plate and Ataractic and twenty minor plates Antarctic plate) and twenty minor plates. These plates are moving in relation to each other due to thermal convective currents originating deep within the earth. Thus, all the tectonic events take place along the margins of the plate.
Earthquakes cannot be prevented from occurring but their impacts can be minimised by taking effective steps to reduce their severity, frequency and possible size. Some effective earthquake management steps are as follows:
1. Earthquake resistant buildings should be constructed in earthquake prone zones. This is done either by keeping weak spots in the house to absorb vibration or by keeping pads or floats beneath the buildings.
2. The earthquake zones should be avoided for settlement and construction of developmental structures.
3. Wooden houses should be preferred in earthquake prone seismic areas.
4. Reinforce concrete columns should support the long walls.
5. There should be reinforced concreted footing for each structure.
6. The earthquake prediction should be made long before its occurrence in order to save life and properties.
(B) Flood and its management:
The overflowing of a river over its banks and submerging the surrounding areas is known as flood. Flood is caused not only due to high precipitation but also due to increased deforestation, poor management of agricultural field, poor drainage system, unplanned urbanization etc.
Flood results in a number of detrimental effects like damaging of houses, buildings, industries etc., damaging of standing crops, lowering of soil fertility, outbreak of epidemics etc. Every year thousands of living organism and huge quantity of properties are lost due to flood in different rivers. Therefore, some preventive measures should be undertaken in order to reduce the severity of flood. Some important abatement steps may be outlined as follows:
1. Dams and barrages should be constructed on river beds.
2. Steps should be taken for the restoration of wet lands and implementation of water shed management programmes.
3. Flood walls embankment and dikes should be constructed as physical barrier.
4. The rivers should b interconnected.
5. There should be massive afforestation over denude areas.
6. There should be proper warning regarding the anticipated flood through different mass media.
7. The Govt. should take emergency flood control measures with active participation of NGOs and local community.
8. Flood water in low lying areas should be diverted through artificially constructed channels bordered by dikes.
(C) Cyclone and its management:
A cyclone is a powerful circular or oval shaped swinkling storm with diameter of about 650 km, capable of causing large scale destruction. The tropical cyclones become highly disastrous because of their high wind speed of 180 to 400 km per hour, high tidal surges, high rainfall intensity, very low atmospheric pressures causing unusual rise in sea level, and their persistence for a longer period of time. The cumulative effects of high velocities of wind, torrential rainfall and transgression of sea water on coastal land create havoc in the affected areas, causing tremendous loss of lives and properties.
The cyclones are called differently in different parts world as Hurricanes in North Atlantic Ocean, Typhoons in the North Pacific Ocean and Willy in sea around. Australia. A super cyclone hit the coastal belt of Orissa on 29th October 1999 which claimed more than 10,000 deaths and loss of more than 2000 crores of rupees.
According to Environmental Scientists, tropical cyclones are the consequences of globed climatic changes and the frequency of cyclones will go on increasing.
So in order to minimise the loss of life and property due to cyclones, the following preventive measures should be undertaken by the present society:
1. There should be massive plantation on the coastal belt.
2. There should be proper warning regarding the anticipated cyclone through different mass media.
3. There should be temporary evacuation of population from affected or to be affected areas to safer places.
4. Efforts should be made to preserve, maintain and replace coastal sand dune.
5. Efforts should be made to maintain and preserve barrier islands and coastal islands.
6. Cyclone proof structures and shelters should be constructed in the areas vulnerable to cyclone hit.
7. The dams, embankments, wind breakers etc. should be constructed in order to prevent the locality from severity of cyclone.
8. Government should take immediate steps to provide relief and rehabilitation measures to the cyclone affected peoples.