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This essay throws light upon the six major natural hazards that occurs in India. The hazards are: 1. Essay on Earthquake 2. Essay on Landslides 3. Essay on Floods 4. Essay on Cyclones 5. Essay on Tsunami 6. Essay on Drought.
Hazard # 1. Earthquake:
India is an earthquake prone country. The areas mostly affected by the earthquake are—the Himalayan region, North-East Indian States, Bihar and Gujarat. About 59% of the country is susceptible to earthquake hazard. The Meteorogical Department has divided the country into five earthquake or seismic zones (Map 11.1).
They are:
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1. Zone I (Least damage risk) covering parts of Punjab, Haryana, UP, Bihar, WB, Godabari basin and desert areas of Rajasthan.
2. Zone II (Low damage risk) includes Southern parts of Punjab, Haryana, West Rajasthan, south UP, Coastal parts of Orissa and Tamil Nadu.
3. Zone III (Moderate damage risk) includes South-eastern Rajasthan, Madhya Pradesh, Karnataka, Maharashtra and South Bihar.
4. Zone IV (High damage risk) includes J & K, Himachal Pradesh, Northern parts of Punjab and Haryana, Delhi, West UP, foothills of the Himalayas and Sikkim.
5. Zone V (Very High damage risk) includes parts of J & K, Himachal Pradesh, Uttarakhand, North-east Indian States and Kutchh region of Gujarat.
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Some Major Earthquakes in India:
The magnitude of earthquake is measured by the instrument called Seismograph. The scale used is called Richter scale as it was developed by seismologist Charles Richter. The magnitude of 3 is the mildest and magnitude of 9.6 is the severest.
The magnitude of more than 6.0 is destructive. Some of the major earthquakes with magnitude of more than 7.5 on Richter scale that occurred are—in Kumaon Region of Uttarakhand (7.5) in 1803, in Ahmedabad of Gujarat (8.0) in 1819; in Cachar of Assam (7.5) in 1869; in Shillong of Meghalaya (8.7) in 1897; in Kangra of Himachal Pradesh (8.0) in 1905; in Bihar—Nepal (8.3) in 1934; in Upper Assam (8.6) in 1950 and Bhuj of Gujarat (7.9) in 2001.
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These earthquakes caused extensive damages to properties and loss of human life. The other damages include—changes in the course of rivers, landslides, creation of new streams and waterfalls, destruction of roads, railways, bridges, telephones and electric lines and mostly the houses and buildings.
Risk reduction measures:
Community preparedness is very important. Strict adherence of building codes and public education are some of the measures for mitigating earthquake impact.
Hazard # 2. Landslides:
The rapid sliding of large mass of rocks, soil and mud along the slope of hill, mountain and highlands is termed as landslides. The landslides may occur due to heavy rainfall on the mountain slopes having loose soil and debris, due to excavation or due to deposition of loose ash after volcanic eruption. Sometimes, landslides may occur due to earthquakes and sudden rock failures.
The areas prone to major landslides in India are:
1. Himalayas and the North-eastern mountain regions
2. Western Ghats and Nilgiries
3. Kashmir, Himachal Pradesh, Uttarakhand and Satluj river basin.
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Landslides bring extensive damages to life and properties of the people. A major landslide occurred in Assam in 1991 in which 300 people killed, roads disrupted and buildings damaged. A massive landslide occurred in Nagaland in 1993 which took away 500 lives and damaged 200 houses. Kohima, the capital of the state remained cut off from the rest of the country for several days.
During the same year landslides also occurred in Itanagar (Arunachal Pradesh), Kalimpong (West Bengal) and Nilgiries. Every year some landslides take place in different places of the country. Majority of the landslides occur during monsoon season in India.
The risk of landslides can be reduced by:
1. Making the foundations of the houses strong.
2. Installation of flexible pipes and underground cables.
3. Forestations and plantations on the slope of the hills.
4. Minimum extent of excavation.
Hazard # 3. Floods:
In the river valleys, flood is a natural phenomenon. However, it becomes hazardous when it causes damages to life and properties.
The flood is caused mainly due to:
1. Occurrence of continued heavy rainfall in the catchments areas of a river or
2. The melting of ice and snow. Sometimes, when heavy downpour occurs for a very short period of time, there could be a sudden flood. Such sudden floods are called Flash floods. Flash floods are very destructive and bring lots of miseries to the people.
3. Large scale deforestation in the catchment areas of a river.
4. Increase in soil erosion
5. Cultivation along the valley side slopes of a river.
6. Construction of embankments and dykes.
7. Changes in the course of a river due to meandering.
8. Increasing urbanization.
The major flood prone areas of the country are the Brahmaputra plain, the Indus—Ganga plain, the Mahanadi and Godabari delta regions. Every year thousand of hectares of crops are destroyed, roads, bridges and railway lines are damaged and bring havoc to the life and properties.
The floods in the country can be controlled to a large extent by:
1. Afforestation in the catchment areas of the river.
2. Protecting the natural forests.
3. Construction of dams and reservoirs.
4. Diversion of flood water to low lying areas.
Hazard # 4. Cyclones:
Cyclones represent low pressure depressions and cause havoc in the areas concerned. They generally have a diameter of 650 kilometres. Tropical cyclones are the most powerful, destructive, dangerous and deadly atmospheric storms on the earth. They are known by different names in different parts of the world. In the Caribbean Sea and south-eastern USA, they are known as Hurricanes, Typhoons, in Bangladesh Cyclones and in Australia Willy Willy.
Impact of Cyclones:
(i) High wind speed of 180 to 400 kilometre s per hour.
(ii) Very heavy rainfall.
(iii) Very low atmospheric pressure causing unusual rise in sea level.
(iv) Rise in sea level leading to submergence of coastal areas and great damage of human lives and property.
(v) Destruction of buildings, transport systems, water and power supply, disruption of communication system.
(vi) Destruction of agricultural crops, domestic and wild animals, natural vegetation.
Cyclonic hazards in India:
Cyclones very often hit the eastern coastal areas of India and come from Bay of Bengal. The states most affected by the cyclonic storms are West Bengal, Orissa, Andhra Pradesh and Tamil Nadu.
The strongest and most notorious cyclone hit the Andhra Coast on May 9, 1900. Nearly, 600 people lost their lives and 300,000 people were rendered homeless, 90,000 cattle perished and property worth Rs. 1000 crores was destroyed. This cyclone is termed as most notorious because it shifted its course almost by 90 degrees.
This was expected to strike southern coast of Tamil Nadu but it shifted northwards and eventually hit the Andhra Pradesh. Some of the districts of Andhra Pradesh were severely affected by the powerful storm caused by strong winds with a speed of 225 to 250 kilometres per hour.
A Supper Cyclone hit the Orissa Coast in Oct. 1999. It was the strongest cyclone in the cyclone history of India. This cyclone moved with a velocity of 300 kms per hour and became stationary for 8 hours over this vast area. Tidal surges of 9 m high were generated and water inundated nearly 15-20 km inside the coastal region.
More than ten thousand people were killed and 200 villages were completely washed away. Several hundreds of thousand cattle perished and countless people were rendered homeless. The standing Kharif crops on 1.75 million hectares were destroyed. The loss of property was estimated at Rs. 10,000 crore. Supply of water and power was disrupted.
The communication system totally failed. Paradeep port was so greatly damaged that it became un-operational for weeks. Surface and ground water was greatly polluted due to dead bodies of humans and animals. The cyclone left of epidemics and hunger and starvation.
In July, 1998, a very powerful cyclone struck Gujarat Coast with a velocity of more than 200 km. per hour and produced tidal waves of 8 m height. The storm was so severe with heavy rainfall that it washed away the salt workers, destroyed human settlements from Surat (Gujarat) to Jodhpur (Rajasthan). Mud-built houses were flattened. The communication system was severely affected. The storm caused more than 1000 human deaths and there was huge economic loss. Kandla port was greatly damaged and it took months to make it operational.
In general, 12 to 13 tropical cyclones with wind speed of nearly 60 km. per hour occur every year in the northern Bay of Bengal. About 5 of these tropical cyclones become strong and severe. The disastrous cyclones occur every five years.
Measures to cope with cyclonic hazards:
India has set up more than 100 disaster warning systems. INSAT 1-B provided important information about disasters cyclones of Andhra in 1990.
Hazard # 5. The Tsunami:
A Tsunami is a Japanese word meaning “harbour wave”. In the past, Tsunamis were referred to as “Tidals waves” or “Seismic Sea waves”. However, both the terms appear to be misleading as there are some causes of Tsunamis other than tides and earthquakes.
The main causes of Tsunami are:
(i) Movement of plates i.e. plate tectonics
(ii) Earthquakes
(iii) Landslides
(iv) Volcanic eruptions
(v) Cosmic collisions.
The main difference between Tsunamis and other water waves are:
(i) Tsunamis are caused by the factors mentioned above while the waves are generated normally by wind.
(ii) The waves are characterized by shallow water with long periods and wavelength.
(iii) A Tsunami on the other hand has a wavelength more than 100 km and period of one hour or more.
(iv) The height of wave of Tsunami is more than 10 metres and speed of about 700 km per hour.
In India, some major Tsunamis occurred in June 1941, Nov. 1945 and Dec. 26, 2004. The Tsunami that occurred in Dec. 2004 affected the east coastal areas of Tamil Nadu, Andhra Pradesh and Andaman and Nicobar islands. The waves measured around 10 metre high and killed 9595 peoples. A huge Tsunami occurred in Japan’s north-east coastal region on March 11, 2011.
The Tsunami was triggered by Japan’s most powerful earthquake in nearly 125 years. It swept away houses, ships, cars, etc., all that came on its way, killing thousands of people in the country. The quake struck at around 2.46 p.m. (Japan’s local time) and alerts were issued across the Pacific ocean. It unleashed the deadliest devastation in the history of the world. Alerts were issued in the coastal areas of South America, Canada, New Zealand, Australia and Alaska.
An 8.8 magnitude earthquake – the largest earthquake in the last 125 years – occurred in the Pacific ocean. A minimum of 300-400 bodies were found in the Wakabayashi area of Sendai city. The wave train which reached the coast ranged from 13 to 33 metres high. The waves travelled at a speed of 4000 kms/hr. The earthquake most affected Sendai city, which is 400 kms away from the capital Tokyo.
The Tsunami waves were generated from 24 kms deep in the sea level. During this devastation, more 4han 40 lakhs people were left homeless. The Government of Japan declared a state of emergency after the earthquake. The disaster also left the entire region in darkness, without power. Tsunami waves that hit Japan’s Miyagi and Fukushima city caused tremendous damage and destruction. The Tsunami also flooded the Sendai Airport, and the airport was declared closed.
This was indeed one of the deadliest devastations seen in recent history. This Tsunami revived memories of the 2004 Tsunami and the disaster that it brought to Asia. The measures to reduce the effect of Tsunami include: Plantation of trees in the costal region; developing early warning system and adopting new national policy on disaster management like creation of awareness among the people, undertaking of projects for reduction during the pre-disaster phase, making disaster management a part of general and technical education and other such measures.
Hazard # 6. Drought:
The absence or deficiency of rainfall in an area for a long time leads to drought. Drought may occur over a small area, over a very large area and especially during the dry season of the year. Drought causes deficiency of soil moisture, make the land unproductive and damages the crops. If drought is persistent for a very long time, it will ultimately lead to aridity. Therefore, semiarid and arid regions are prone to droughts.
Based on the causes, nature and character, drought can be classified as:
(i) Hydrological drought—when water level of the surface and ground falls
(ii) Meteorological drought—when average annual rainfall is 25% less than the normal
(iii) Agricultural drought—when soil moisture goes below the level needed for plant growth
(iv) Ecological drought—when a natural ecosystem degraded resulting in the death of a large number of animals and trees in the forest
(iv) Socio-economic drought—when the demand supply gap of goods and services has widened.
Drought affected Areas:
In India, the Irrigation Commission has identified 67 districts as drought affected where there is less than 10 cm of mean annual rainfall. In these districts, 25% of cropland and 12% of population are affected by drought.
Three Zones have been identified as severely drought prone areas in the country:
1. Desert and Semi-arid regions:
It extends from Ahmedabad to Kanpur on one side and Kanpur to Jalandhar on the other and covers nearly 600,000 sq. km. Average Annual Rainfall in this region is less than 7.5 cm.
2. Rain-shadow Areas of Western Ghats:
It is situated on the eastern side of the Western Ghats where Annual Average Rainfall is less than 7.5 cm. It covers areas of south-western Andhra Pradesh, eastern Karnataka and south-western Maharashtra.
3. Scattered Zone:
The scattered zones cover areas of Tirunelveli and Coimbatore districts of Kerala, Palamau areas of Jharkhand, Purulia district of West Bengal and Kalahandi region of Orissa.
Impact of drought:
Drought affects the environment and economy resulting in poor— standard of living. The environmental impact includes—some plants and animals perish as they cannot withstand extreme drought and migration of animal takes place.
The economic impact includes—decrease in production resulting in shortage of food grains; decrease in fodder production leading to decrease in productivity of cattle and decrease in the production of agro- based industries. The demographic impact includes—migration of people and poor living conditions.
Drought Control Measures:
It is not very easy to forecast drought. Now a days, computer based studies help to get some ideas about it.
Some of the measures to mitigate drought are:
(i) Efficient use of rain water and rain harvesting
(ii) Introduction of dry farming techniques
(iii) Lining of canals to prevent water loss
(iv) Avoidance of over cropping
(v) Limiting settlements in drought prone areas
(vi) Introduction of horticulture plantation and
(vii) Checking of desert migration.