Welcome dear students! Today we are going to learn about India Natural Disasters from Class 10 Social Science. In this chapter, we will understand natural disasters such as earthquakes, floods, cyclones, landslides, and coastal erosion. We will study their causes, effects, preventive measures, and the areas they affect. Many incidents occurring in nature are beyond human control. Preventing these and predicting their occurrence at a certain place is beyond science too. Naturally occurring destructive incidents resulting in loss of human life and property are called natural disasters. Of these natural disasters, earthquakes, floods, heat waves, droughts, cyclones, landslides, coastal erosion, avalanche, and cloud burst are destructive. Let us begin our study with cyclones.
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Cyclonic winds are among the most dangerous and destructive natural disasters occurring on the surface of the earth. These winds are called cyclones. Cyclones originate in the Bay of Bengal. Because the Bay of Bengal is surrounded by land on three sides, it is subject to intense heating. This gives rise to humid and unstable air masses that cause cyclones. Usually, they originate in the Bay of Bengal and blow westwards, reaching the Tamil Nadu or Andhra coast. Sometimes, they change their direction to the northwest, hitting the Odisha or West Bengal coast. The occurrence of cyclones in India happens mainly in two periods. They are more frequent in October to November and also occur in May to June. Recently, due to the increase in global warming, cyclones also occur in the Arabian Sea. Examples include Gonu in 2007, Nilofer in 2014, Nisarga in 2020, and Tauktae in 2021.
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Do you know this? According to an international treaty of 2004, cyclones are given certain names. As per this agreement, countries having the northern Indian oceanic coast like Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka, and Thailand communicate the names to a committee working under the India Meteorological Department, from which the names are selected one after the other at Delhi. The cyclone that occurred recently was named Laila by Pakistan. Later names of cyclones were, respectively, Sri Lanka's Bandoo, Thailand's Phet, Bangladesh's Giri, India's Tej, Maldives' Kaila, Myanmar's Thane, and Oman's Mujan. Now let us look at the effects of cyclones. Cyclones are very destructive. Sometimes, the life of the people of cyclone hit areas gets totally changed. They cause large scale deaths. Ocean tides inundate the inland water bodies and make them salty. Crops get totally destroyed. Transport links, electricity supply, and the daily life of the people get affected badly. Cyclone hit areas suffer from infectious diseases, leading to huge casualties.
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To prevent these damages, several measures must be taken. We must ensure the evacuation of people from low lying areas. Authorities must be ready with generators, boats, helicopters, and other transport facilities. Trains and buses should be re routed from cyclone prone areas. People must be kept constantly informed about the movement of the cyclone. Army battalions must be kept ready. Food, potable water, and clothes must be kept ready. Medicines and medical facilities must also be kept ready. Next, we will learn about floods. Among the natural calamities faced by India every year, floods are the most dangerous. When there is heavy rainfall and excessive melting of ice, the volume of water increases in the river leading it to overflow. This is called floods. The river water, not being able to flow in the river course, overflows and occupies low lying areas on either side. Sometimes, due to more rainfall in a particular area, the rivers swell.
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Do you know this? The recent floods of the Mandakini river in Uttarakhand state at Kedarnath on July 17, 2013, were the most destructive. Let us examine the causes for floods. The uncertainty of monsoon rainfall sometimes brings heavy rainfall that causes floods. Accumulation of silt in the rivers leads to overflowing of water on either side of the river, causing floods. Breach of dams or retention walls leads to sudden release of large quantity of water resulting in floods. Rivers changing their course can also cause floods. Heavy rainfall during cyclones can also lead to floods. Earthquakes in the sea also cause floods. Apart from these natural causes, man made causes like deforestation, improperly built dams and bridges, weak retention walls, and illegal encroachment of land are also important causes. Flood prone regions are found all over the country. The Ganges and its tributaries Yamuna, Gandak, Kosi, and Ghagra rivers cause floods in Uttar Pradesh and Bihar.
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Damodar and Suvarnarekha rivers cause floods in Chhattisgarh and West Bengal states. Brahmaputra and its tributaries Dibang, Dihang, Subansiri, and Lohit rivers cause floods in Assam. Cloudburst often causes abrupt floods in Jammu and Kashmir, Himachal Pradesh, and Sikkim in the Himalayas. Narmada, Tapti, Sabarmati, and Mahi rivers cause floods for some days in a year in the state of Gujarat. Krishna, Tungabhadra, Ghataprabha, Malaprabha, Dhoni, and Bennehalla cause floods during the rainy season in Karnataka. The effects of floods include loss of shelter, property, land, and crops of the people. Telecommunication, electricity supply, and transport facilities get affected. Besides washing away the fertile upper layers of soil, a lot of trees are destroyed. Stagnant water in the low lands leads to dangerous diseases. To control floods, bunds should be constructed on either side of rivers.
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Constructing dams across rivers, collecting water in reservoirs, and directing the water to other places is essential. Establishing centers to issue flood warnings is crucial. Afforestation in the river basins will prevent soil erosion, and also reduce accumulation of silt in the rivers, thereby reducing the chances of floods. Moving on to our third topic, landslides. Land mass sliding down the slopes from mountains or hills are called landslides. Among the things that come down along with the sliding land mass, stones, mud, and debris are important. Landslides occurring in the steep mountainous regions are more destructive. In the Himalayan region, along with landslides and snowfall, it causes destruction to human life also. The causes for landslides include constantly flowing water and tides in mountainous areas and coasts that remove soil, creating slopes leading to landslides. When railways, roads, and canals are constructed in steep mountainous areas, the slopes become steeper, leading to landslides.
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Collection of loose soil on a clay soil layer can enhance steep slope formation, leading to landslides. Landslides are common in mining areas. Excavation of earth to reach ore deposits deep down can cause landslides. Deforestation and deep tilling of the slopes can also cause landslides. The effects of landslides are severe. Flowing small rivers are checked by landslides. Transportation is affected. Streams and many plants get submerged. Landslides can cause loss of life and damage to property. Now let us study coastal erosion. Sea waves continuously hit the coast. Because of this, the coastal land is eroded. The erosion of land by the waves in the coastal areas is called coastal erosion. Coastal erosion is more during the south west monsoon season because of high tides. During this period, very high waves from the Arabian Sea bash the coast, engulfing a huge land mass. Because of this, coastal erosion is more severe along the west coast of Kerala, Karnataka, and Goa.
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In addition, the Kanyakumari region of Tamil Nadu, Maharashtra, and Gujarat are also affected by coastal erosion. Coastal erosion is very less on the east coast. The effects include a large amount of land mass submerging into the sea due to coastal erosion by waves. Many houses and property get lost and damaged. Prevention methods are vital. We must prohibit sand mining in coastal areas. We must construct retention walls along the length of the coast wherever waves are strong. Stocking large rocky boulders along the coast helps reduce the impact. The most effective method of preventing coastal erosion is by growing mangrove forests along the coast. Let us now turn to earthquakes. Earthquakes are one of the most important natural calamities occurring on the land surface. Vibration or movement of the upper layers of the earth due to the pressure created inside is called earthquake. Due to this, the surface of the earth shakes.
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The reasons for earthquakes are as follows. First, pressure increases in the interior of the earth. Second, movement of magma from one part to another. Third, urbanisation. Fourth, deforestation, construction of dams, and mining activities. The distribution of earthquakes in India is fairly widespread. The northern Himalayas, East Assam, and Gujarat in the West have witnessed most of the earthquakes. In South India, Koyna, Latur, and other places have experienced some earthquakes. If you look at the map provided in your textbook, you will see earthquake and flood prone regions marked across the country, including locations like Dhubri, Porbandar, Latur, Balasore, Nellore, and Puducherry. The effects of earthquakes include loss of life and destruction of property, obstruction to transport, spread of infectious diseases, increased tidal activity, tsunamis, and change in river direction. Precautionary measures to be taken include restricting construction of multi storied buildings in earthquake prone areas.
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Using very light material for construction of houses in these areas is recommended. Constructing houses to ensure stability is essential. Providing basic amenities to quake affected areas must be prioritized. Disconnecting power supply in the event of an earthquake is a critical safety step. Regarding remedies during natural disasters, measures to be taken include the distribution of food, drinking water, distribution of medicine, temporary shelter facilities, necessary basic amenities, and essential services to be provided. Now, let us move to the exercises section to reinforce your understanding. I will answer each question completely so you can prepare effectively for your exams.
Question one asks, what are natural disasters? Naturally occurring destructive incidents resulting in loss of human life and property are called natural disasters. Examples include earthquakes, floods, heat waves, droughts, cyclones, landslides, coastal erosion, avalanche, and cloud burst. Question two asks, what are the effects of cyclones? Cyclones are very destructive and can totally change the lives of people in hit areas. They cause large scale deaths, inundate inland water bodies making them salty, totally destroy crops, badly affect transport links and electricity supply, and lead to infectious diseases causing huge casualties.
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Question three asks, what are floods? When there is heavy rainfall and excessive melting of ice, the volume of water increases in the river leading it to overflow. This is called floods. The river water overflows and occupies low lying areas on either side. Question four asks, what is a landslide? Land mass sliding down the slopes from mountains or hills are called landslides. Stones, mud, and debris come down along with the sliding land mass. Question five asks, what is an earthquake? Vibration or movement of the upper layers of the earth due to the pressure created inside is called earthquake. Due to this, the surface of the earth shakes. Question six asks, what are the causes of floods and to describe flood prone areas in India. The causes are uncertainty of monsoon rainfall, accumulation of silt in rivers, breach of dams or retention walls, rivers changing course, heavy rainfall during cyclones, earthquakes in the sea, and man made causes like deforestation, improperly built dams and bridges, weak retention walls, and illegal encroachment.
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Flood prone areas include the Ganges and its tributaries Yamuna, Gandak, Kosi, and Ghagra in Uttar Pradesh and Bihar. Damodar and Suvarnarekha in Chhattisgarh and West Bengal. Brahmaputra and its tributaries Dibang, Dihang, Subansiri, and Lohit in Assam. Cloudburst areas in Jammu and Kashmir, Himachal Pradesh, and Sikkim. Narmada, Tapti, Sabarmati, and Mahi in Gujarat. And Krishna, Tungabhadra, Ghataprabha, Malaprabha, Dhoni, and Bennehalla in Karnataka. Question seven asks, what is coastal erosion and to mention its management. The erosion of land by the waves in the coastal areas is called coastal erosion. Management includes prohibiting sand mining, constructing retention walls, stocking large rocky boulders along the coast, and growing mangrove forests. Question eight asks to write about the effects of earthquakes and precautions to be taken. Effects include loss of life and property destruction, obstruction to transport, spread of infectious diseases, increased tidal activity, tsunamis, and change in river direction. Precautions include restricting multi storied buildings, using light construction materials, ensuring house stability, providing basic amenities, and disconnecting power supply during an event.
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Now let us cover the activities and project work. For the first activity, you must mark the earthquake prone and flood affected regions on the Indian map. Use your atlas to locate the northern Himalayas, East Assam, Gujarat, Koyna, Latur, and the river basins we discussed, and shade them appropriately on your outline map. For the second activity, discuss in the class about the uses of naming cyclones. As per the 2004 international treaty, naming cyclones helps in clear communication, avoids confusion when multiple storms occur, aids in tracking and issuing warnings, and makes it easier for the public and media to remember and follow safety instructions. For the project, with the help of your teacher, make a list of the flood affected places in India. You can compile data from recent news, government disaster management reports, and your textbook to create a comprehensive list covering states like Assam, Bihar, Uttar Pradesh, Kerala, and Karnataka.
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Remember, understanding these natural disasters, their causes, effects, and preventive measures is crucial for your board examinations and for developing awareness about disaster management in our country. Review the definitions carefully, memorize the lists of affected regions and rivers, and practice labeling the map locations. Thank you for listening! Keep revising and practicing. Goodbye! [CHAPTER_COMPLETE]