The environmental hazard is an important area of physical geography in which the geographers are increasingly concentrating and probing. Although many of environmental problems are clearly of man’s own making, other arise from purely natural phenomena. Severe catastrophes such as floods or violent storms are generally referred to environmental hazards.
Natural Hazards: Throughout the human history man has been adversely affected by natural disasters. In fact, they have been an integral part of human history right from the dawn of culture and civilization. Some of the environmental disasters become hazards because man elects to use areas susceptible to these natural phenomena; this applies especially to earthquakes and floods. The perception about environmental hazards varies with culture, economic development and time. The natural hazards include (i) volcanic eruptions, (ii) earthquakes, (iii) landslides, (iv) tornadoes, (v)hurricanes, typhoons, cyclones etc. (vi) storm surges, (vii) floods, (viii) droughts, (ix) blizzards, (x) epidemics, and (xi) forest fires.
According to the World Disaster Report 2010 published by the International Federation of Red Crescent Societies (IFRC), during the period 2000 to 2009, as many as 85 percent of people affected by disasters belonged to the Asia Pacific region. The Global Assessment Report 2011 published by the United Nations International Strategy for Disaster Reduction (UN ISDR) estimates that more than 90 per cent of the global population exposed to floods lives in South Asian, East Asian and Pacific countries. Among the disaster-prone countries in South Asia , India and Bangladesh are highly vulnerable due to the large size of population exposed to disasters and the geo-climatic conditions.
According to UNISDR, in the year 2010, India ranked second in the world for natural disasters after China. India’s hazards profile is mainly determined by the geo-climatic setting and topographic features. Climate induced hazards rank high in terms of frequency, impact and uncertainties of occurrence.
Types of Disasters
The disasters affecting the humanity and society may be classified under the following categories:
1. Geological: Earthquakes, tsunamis, landslides, avalanches,
2. Climatic : Cyclones, sea-surge, storms associated coastal erosion. Floods and droughts.
3. Environmental degradation:
4. Disasters by biological factors: epidemics and public health crises
5. By hostile elements: war, terrorism, extremism, insurgency
6. By disruption /failure of major infrastructure facilities
7. By large crowds getting out of control
Earthquakes: Earthquake is a release of energy that produces shaking in Earth’s crust at the moment of rupture along a fault or in association with volcanic activity. Earthquake magnitude is estimated by the Richter Scale, intensity is described by the Mercalli Scale.
Earthquakes occur when two tectonic plates move suddenly against each other. The rocks usually break underground at the focus (hypocenter) and the Earth shakes. Waves spread from the epicenter, the point on the surface above the focus (hypocenter). If a quake occurs under the sea it can cause a tsunami.
The distribution of earthquakes in the world coincides very closely with that of volcanoes. Regions of greatest seismicity are (i) Circum-Pacific areas, with the epicenters and the most frequent occurrences along the ‘Pacific Ring of Fire’. It is said that as many as 70 percent of earthquakes occur in the Circum-Pacific belt. Another 20 percent of earthquakes takes place in the Mediterranean-Himalayan Belt including Asia Minor, the Himalayas and parts of north-west China. Elsewhere, the Earth’s crust is relatively stable and is less prone to earthquakes, though nowhere can be said to be immune to earth tremors.
Seismicity in India: The seismically highly vulnerable zones of India areas of India include:
(i)The young folded mountains -Himalayas.
(ii) Gulf of Khambat
(iii) Rann of Kachchh in western Gujarat
(iv) Andaman and Nicobar andLakshdweep
Strategy to combat earthquake disasters: Some of the effective steps to reduce the riskfrom earthquakes are:
(i)Improved designs and architecture of buildings.
(ii) Effective rescue and relief camps establishment immediately after the earthquakes.
Cyclone: Cyclone is a dynamically or thermally caused low-pressure area of converging air flows. The cyclones may be divided into (i) the tropical cyclones, and (ii) temperate cyclone.
Tropical Cyclones: A cyclonic circulation originating in the tropics, with winds between 30 and 64 knots (39 to 73 mph); characterized by closed isobars, circular organization, and heavy rains. The tropical cyclones are known by different names in different parts of the country. They are known as hurricanes in the Gulf of Mexico, Gulf of California, USA - North America; typhoons in China; Taifu (Tofu) in Japan; Baguio in Philippines; Willy-Willy in north and east Australia and cyclones in the Indian Ocean.
Characteristics of a Tropical Cyclones:
The main characteristics of a tropical cyclone are as under:
(i) The isobars in a tropical cyclone are circular in shape.
(ii) The diameter of a tropical cyclone varies from 50 to 300 kilometers.
(iii) The central area of a tropical cyclone is known ‘Eye’ of a cyclone.
(iv) They drive their energy from the latent heat.
(v) They occur in the Northern Hemisphere in the autumn season
(vi) They give torrential rainfall.
(vii) They are the most destructive and cause heavy damage in their path.
Origin of Tropical Cyclones: The origin of tropical cyclones is not well understood. The origin of tropical cyclones is, however, quite different from that of the temperate cyclones. The air of the tropics is essentially homogeneous, with no fronts. In addition, the warm air and warm sea ensure an abundant supply of water vapor and thus the necessary latent heat to fuel these storms. The tropical cyclones originate within a warm, humid air mass between 8o and 25o N and South in both the hemispheres. A tropical cyclone usually develops from a small tropical depression. The Coriolis effect also helps in the origin of tropical cyclones.
Structure of a Tropical Cyclone
In India, as many as 200 million people are exposed to recurring floods every year. The Vulnerability Atlas prepared by the Building Materials Technology Promotion Council (BMTPC) about 59 percent of the geographical area in India falls within seismic zones III, IV, and V which could face earthquakes of moderate to very high intensity. About 12 percent of the geographical area covering more than 40 million hectares, faces recurring floods, changing the course of rivers and river erosion. Along the 7516 km coastline, about 5700 km are vulnerable to storm surge, cyclones, and tsunamis. More 68 percent of the cultivable area is vulnerable to drought. Due to the pressure of fast pace of urbanization, industrialization, and modernization, the threats of man-made and technological disasters have also increased substantially as modern industrial units are processing, storing, and transporting hazardous materials.
In the first decade of 21st century, India faced devastating disasters like the Bhuj, India faced devastating disasters like the Bhuj earthquake 2001, the India Ocean Tsunami in 2004, the Kashmir earthquake in 2005, the Kosi floods in 2008, the Andhra Pradesh and Karnataka floods in 2009, the Leh cloudburst and the Uttarkhand floods in 2010, and the Sikkim earthquake in 2011. It is estimated that the cumulative losses from the floods (Kosi floods in 2008, Karnataka floods 2009, Uttarakhand floods in 2010) are estimated to be about RS. 80,000 crores.
Steps to be taken:
(i) Disaster Management Act-2005
(ii) Good governance
(iii) Innovative Systems, Techniquesand Technologies
(iv) Disaster Mitigating Funding
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