Go through these RBSE Class 11 Indian Geography Notes Chapter 11 Natural Disasters and Management contain important concepts so that students can score better marks in the exam.
Rajasthan Board RBSE Class 11 Indian Geography Notes Chapter 11 Natural Disasters and Management
Flood and Drought
- An overflow of a large amount of water out of its normal limits, especially over what is normally dry land. It may be unusual build-up, run-off of surface water or abnormal erosion or undermining of shoreline.
- Floods can also the be overflow of mud caused by build-up of water underground.
- A drought is a period of below average precipitation in a given region, resulting in prolonged shortage in water supply, whether atmospheric, surface water or ground water.
- A drought can last for months or years or may last for as few as 15 days.
- Excess rainfall causes floods, while very little rainfall causes drought.
- During rainy season, uneven distribution of rainfall in India causes floods as well as drought.
- India has a large surface area and monsoon climate and both of these cause flood and drought here.
- More than 4 million hectares of land is affected every year in India due to flood disaster.
Reasons of Flood
- When the water in rivers overflows all around, it takes the form of flood.
- When it is excessive rainfall in the river flow zone, it is unable to get proper and enough way to flow out and when it spreads all round the plains, it is called flood.
- Due to deposition of sediment at the river bottom, its water containing capacity is reduced and so water overflows to cause flood.
- Deforestation, depasturation, settlement in the flow routes of rivers, unplanned development of roads and railways and destruction of traditional water resources are some other reasons for flood in India.
Flood Affected Areas in India
- The form of rainfall controls the situation of flood in India.
- The awful condition of flood is seen in north and north-eastern part of India.
- The rivers that flow in western India lead to lesser flood than that of rivers flowing in eastern India.
- Due to destructive floods in the Rivers Kosi and Damodar, River Kosi is called as the Sorrow of Bihar and River Damodar is known as the Sorrow of West Bengal.
- An awful view of flood can be seen in Brahmaputra river in north-eastern part of India and in Chambal, Son, Betwa rivers in the central part of India.
- In the peninsular coastal regions of India, there are floods due to Rivers Mahanadi, Godavari, Krishna and Cauvery.
Flood as a Problem and Hazard
- In India, flood is the most harmful natural disaster in which thousands of lives are lost every year.
- According to an estimate, there is a loss of 12 lakh livestocks, 12 lakh houses and more than one thousand crore rupees every year due to flood in India.
- Uttar Pradesh, Bihar, West Bengal, Assam and Orissa are the most flood-affected regions.
- Floods disturb the daily life. They block the road and railway network, destroy the crops and water sources are polluted.
- More than 60 per cent of total loss due to floods occurs in Uttar Pradesh and Bihar alone.
Management of Flood
- Management of flood is done at government, society and individual level.
- To check the flood, Flood Control Scheme was started in 1954 in which planning of construction of embankments and water flow drainage was made.
- Under multipurpose projects, dams were built in the flood prone zones and on the Rivers Mahanadi, Damodar, Sutlej, Beas, Chambal and Narmada.
- To control the floods, development of forests, cleaning the river bottom is done, and the embankments are also made strong.
Drought and Its Reasons
- Insufficient rainfall, its uneven distribution and uncertainty are the chief causes of drought.
- Some of the reasons of drought are deforestation, uninterrupted flow of rainwater, destruction of natural water resources, lack of proper water conservation policy and increasing population etc.
- Mainly, shortage of water is the main cause of drought.
Drought Affected Areas in India
- Western India is the most drought-affected area. There is drought in the states of Rajasthan, Gujarat, Haryana, some regions of Madhya Pradesh, central Maharashtra and central and eastern Karnataka at large.
- More than 5 crore people are affected due to drought every year in India.
- India has been divided into two parts on the basis of drought. Western Rajasthan and western Gujarat are included in such areas where affected areas with more than 25 percent uncertainty of drought are found.
- Eastern Gujarat, Eastern Rajasthan, Punjab, Haryana, Uttarakhand, central Maharashtra and southern Andhra Pradesh are included in such areas where affected areas with less than 25 per cent uncertainty of drought.
- Almost 77 districts in India are drought-prone.
Drought as a Problem and Hazard
- More the scarcity of water, more the fierce form of drought.
- There are three forms of drought: famine of food grains, famine of food grains and fodder, and famine of food grains, fodder and water. These three forms are respectively called mono, bi-famine and tri-famine.
- There was a tri-famine in 1987 in Rajasthan, in which thousands of livestock and other living beings were killed.
- The tri-famine which occured in Vikram Samvat 1956 is called the “Trikal of Chhappan” and it is considered as the most horrible famine up till now.
- There is official, social and individual management of drought.
- The remedies of drought include rainwater-harvesting, construction of anicuts, search for new water sources, construction of underground water-tanks in the houses, fencing of the agricultural lands, cultivation of the crops that need less water, and manual cooperation etc.
- The storage of underground water is a simple way to reduce the possibility of drought.
- These are also known as cyclone and are mostly seen in the tropical regions. These cyclones enter into India from Bay of Bengal and Arabian Sea.
- On reaching the internal part of India, speed and intensity of these cyclones is reduced.
- Due to fast blowing with heavy rainfall, they cause great loss of life and property in the coastal regions.
Reason of Origin of Sea Storms
- There are many reasons of origin of sea storms, Some scholars consider that they occur due to fronts. These fronts are formed by the conjunction of different types of winds.
- Some scholars believe that sea storms are the result of convection process. Atmospheric pressure is the main cause of their occurrence.
Sea Storm Affected Areas, Problem and Management
- The affected areas of sea storms in India include the coastal regions of Gujarat, Bay of Bengal, Andhra Pradesh, Orissa and West Bengal.
- Activities like getting information related to sea storms from satellites and its broadcasting through radio, television and other means of communication, banning the entry of sailors in the sea during the storm period, implementing collective insurance plan, showing individual honesty and loyalty to carry the elderly, children and women to safe places and social cooperation are included under sea storm management.
- For minimizing the intensity of floods, Forecast Organisation was established in 1954 by the government of India. Other remedies for avoiding the intensity of flood include keeping distance from water resources and individual safety.
Natural Disasters and Management Notes Important Terms
→ Natural Disasters: The natural changes harming the human society are called natural disasters.
→ Flood: An overflow of a large amount of water beyond its natural limits, especially over what is a normally dry land.
→ Sea storm: A centre of low pressure, popular in the name of cyclone, in which the wind, violently blow from the outside towards the centre. These are called tropical cyclones.
→ Climate: The composite or generally-prevailing weather conditions of a region such as temperature, air pressure, humidity, precipitation, sunshine, cloudiness and winds throughout the year, averaged over a long time period.
→ Season: The seasons are the main periods into which a year can be divided and each of which have their own typical weather conditions.
→ Sedimentation: It is the tendency for particles in suspension to settle out of the fluid in which they are contained and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them. These forces can be due to gravity, centrifugal acceleration or electro-magnetism.
→ Desert: An arid land with usually sparse vegetation, especially, such land having a very warm climate and receiving 25 cm and lesser rainfall annually.
→ Sea storm: Storm conditions out at sea are defined as having sustained winds of 48 knots (90 km/h) or greater.
→ Tsunami: A long high sea wave caused by an earthquake or other disturbance or volcanic eruption.
→ Peninsula: An area of land almost completely surrounded by water from three sides or projecting out into a body of water.
→ Wharf: A structure built on the shore or projecting into a harbour, stream etc. so that vessels may be moored alongside to load or unload cargo, or to lie at rest, Guay, Pier, to tie up at a wharf.
→ Drought: A drought is a period of below average precipitation in a given region, resulting in prolonged shortage in water supply, whether atmospheric, surface water or ground water.
→ Gulf or Bay: A deep inlet of the sea almost surrounded by land, with a narrow mouth, a deep ravine, chasm or abyss.
→ Communication: The imparting or exchanging of information by speaking, writing or using some other medium.
→ Dam or Embankment: A barrier constructed to hold back water and raise its level, forming a reservoir used to generate electricity or for water supply.
→ Soil: The upper layer of earth in which plants grow, a black or dark-brown material typically consisting of a mixture of organic remains, clay and rock particles.
→ Erosion: A dynamic process in which surface soil and rock are worn away through the action of glaciers, water and wind.
→ Soil Erosion: It is the displacement of the upper layer of soil; one form of soil degradation.
→ Irrigation: The supply of water to land or crops to assist in their growth, typically by means of channels in dry season.
→ Underground water: Ground water is also called underground water. The water beneath the surface in soil pore spaces and in the fractures of rock formations.
→ Industry: A change of primary products into more beneficial and useful objects is called industry.
→ Remote sensing: It is the science of obtaining information about objects or areas from distances, typically from aircraft or satellites.
→ Geographic Information System: The latest system of collecting data.
→ Tanka: It is a traditional rainwater harvesting technique common to the Thar Desert region of Rajasthan. A tanka is a cylindrical underground rainwater storage system.
→ Torrid tropical zone: The part of the Earth’s surface between the Tropic of Cancer and the Tropic of Capricorn, charaterized by hot climate. Also known as Torrid zone.
→ Front: A front is a weather system that is the boundary separating two different types of air.
→ Equator: The imaginary great circle around the earth’s surface, equidistant from the poles and perpendicular to the earth’s axis of rotation. It divides the earth into the Northern Hemisphere and the Southern Hemisphere.
→ Airmass: An air mass is a volume of air defined by its temperature and water vapour content.
→ Convection: It is the circular motion that occurs when warmer air or liquid air which has faster moving molecules, making it less dense, rises, while the cooler air or liquid settles down.
→ Atmospheric Pressure: The pressure exerted by the earth’s atmosphere at any given point, being the product of the mass of the atmospheric column of the unit area above the given point and of the gravitational acceleration at the given point.
→ Atmosphere: It is a thin layer of gases that surrounds the earth.
→ Turbulence or disturbance: A state or condition of confusion, movement or agitated disorder.
→ Latitude: Latitude is a geographic coordinate that specifies the north-south position of a point on the Earth’s surface.
→ Temperate zone: The part of the Earth’s surface between the Arctic Circle and the Tropic of Cancer or between the Antarctic Circle and the Tropic of Capricorn, characterised by temperate climate.
→ Mavath: The rainfall in North-Western India during the winter season caused by tropical cyclones.
→ Satellite: An artificial body placed in the orbit round the earth or another planet in order to collect information or for communication purpose.
→ Citizen: An inhabitant of a city or town, especially one entitled to the rights and privileges of a freeman.
→ Pressure Gradient: Pressure Gradient describes in which direction and at what rate the pressure changes most rapidly around a particular location.