UNIT-III
Que 1. What is Flood? Write damages caused due to flood. (Summer-14, 15)
OR….Explain flood hazard in India.
A flood is usually caused by rain, heavy thunderstorms, and thawing of snow.
It’s considered to be a temporary condition of two or more acres of dry land either:
— Overflowed with inland or tidal waters
— Mudflows
How does Flooding Start and end?
Ø The shore or land by or surrounding a body of water erodes and this erosion causes waves currents that result in a flood.
Ø Flood disasters have been increased because of the expansion of settlements and growth in floodplains.
Ø Floods could be slow or fast but usually occur over a matter of days.
Ø After the water eventually goes down or dries up. On coastal floods, low tides and high tides makes a change in heights.
Where does flooding occur?
— Flooding is the most worldwide natural disaster. It occurs in every country and wherever there is rainfall or coastal hazards.
— They are most likely to happen in tropical areas.
— Most common floods happen around the world’s largest/greatest rivers.
— Believe it or not, smaller rivers could cause more damage even though people don’t pay as much attention to them.
— Most Flooding occurs during the beginning of spring.
Damages caused due to flood
— 1. Physical damage – structures damaged or collapsed by washing waters, landslide triggered on account of water getting saturated. Boats and fishing equipment’s may be lost or damaged in coastal areas.
— 2. Casualties and pubic health – people and livestock deaths caused by drowning, very few serious injuries. Outbreak of epidemics, diarhea, viral infections, malaria.
— 3. Water supplies – contamination of water (wells, ground water, piped water supply). Clean water may be unavailable.
— Crops and food supplies – sudden food shortage can be caused due to loss of entire harvest, spoiling of grains when saturated in water along with loss of animal fodder.
— The crop storage facilities and go downs may get submerged resulting in immediate food shortage. Floods may also affect the soil characteristics. The land may be rendered infertile due to erosion of top layer or may turn saline if sea water floods the area.
Que 2. What are Do's and Dont's during Earthquake? (Summer-14, 15)
What to Do Before an Earthquake
— Repair deep plaster cracks in ceilings and foundations. Get expert advice if there are signs of structural defects.
— Anchor overhead lighting fixtures to the ceiling.
— Follow BIS codes relevant to your area for building standards.
— Fasten shelves securely to walls.
— Place large or heavy objects on lower shelves.
— Store breakable items such as bottled foods, glass, and china in low, closed cabinets with latches.
— Hang heavy items such as pictures and mirrors away from beds, settees, and anywhere that people sit.
— Brace overhead light and fan fixtures.
— Repair defective electrical wiring and leaky gas connections. These are potential fire risks.
— Secure water heaters, LPG cylinders etc., by strapping them to the walls or bolting to the floor.
— Store weed killers, pesticides, and flammable products securely in closed cabinets with latches and on bottom shelves.
— Identify safe places indoors and outdoors.
— Under strong dining table, bed
— Against an inside wall
— Away from where glass could shatter around windows, mirrors, pictures, or where heavy bookcases or other heavy furniture could fall over
— In the open, away from buildings, trees, telephone and electrical lines, flyovers and bridges
— Know emergency telephone numbers (such as those of doctors, hospitals, the police, etc)
— Educate yourself and family members
Important dont’s in the earthquake
— Do not stand in doorways. Move away from window, mirror, bookcases and unsecured heavy objects.
— Avoid places where there are loose electrical wires and do not touches metal objects.
Que 3. Explain various regions of our country prone to flood.
India, being a peninsular country and surrounded by the Arabian Sea, Indian Ocean and the Bay of Bengal, is quite prone to flood. As per the Geological Survey of India (GSI), the major flood prone areas of India cover almost 12.5% area of the country.
Every year, flood, the most common disaster in India causes immense loss to the country's property and lives.
India Flood Prone Areas
The states falling within the periphery of "India Flood Prone Areas" are West Bengal, Orissa, Andhra Pradesh, Kerala, Assam, Bihar, Gujrat, Uttar Pradesh, Haryana and Punjab. The intense monsoon rains from southwest causes rivers like Brahmaputra, Ganga, Yamuna etc. to swell their banks, which in turn floods the adjacent areas.
Over the past few decades, central India has become familiar with precipitation events like torrential rains and flash floods. The major flood prone areas in India are the river banks and deltas of Ravi, Yamuna-Sahibi, Gandak, Sutlej, Ganga, Ghaggar, Kosi, Teesta, Brahmaputra, Mahanadi, Mahananda, Damodar, Godavari, Mayurakshi, Sabarmati and their tributaries.
Ø Ganga Basin:The Ganga Basin gets flooded mostly in the northern part by its northern tributaries. The badly affected states of the Ganga basin are West Bengal, Bihar and Uttar Pradesh.
Besides the Ganga, rivers like Sarada, Rapti, Gandak and Ghagra causes flood in eastern part of Uttar Pradesh. The Yamuna is famous for flooding Haryana and Delhi. Bihar experiences massive dangerous flood every year. River Burhi, Bagmati, Gandak, Kamla along with many small rivers contribute to that. In West Bengal, rivers like Mahananda, Bhagirathi, Damodar, Ajay etc. causes floods because of tidal effects and insufficient river channels.
Ø Brahmaputra and Barak Basins:The river banks of Brahmaputra and Barak gets flooded due to the Surplus water found in the Brahmaputra basin and the Barak basin. These rivers along with their tributaries flood the northeastern states like West Bengal, Assam and Sikkim. Jaldakha, Teesta and Torsa in northern West Bengal and rivers in Manipur often overflow their banks.
Ø Central India and Deccan Rivers Basin: In Orissa, spilling over of river banks by Mahanadi, Baitarni and Brahmani causes havoc. The deltaic area formed by these three rivers is thickly populated. Even some small rivers of Kerala and mud stream from the nearby hills add on to the destruction. Southern and central India observes floods caused by Narmada, Godavari, Tapi, Krishna and Mahanadi due to heavy rainfall. Cyclonic storms in the deltaic regions of Godavari, Mahanadi and Krishna even floods the coastal regions of Andhra Pradesh, Orissa and Tamil Nadu occasionally.
Que. 4. Describe the monsoon in India and its effect.
OR…What is the effect of monsoon in India?
§ A name for a wind system that changes in speed and direction with season.’ (derived from an Arab word)
OR
§ The term technically describes seasonal reversals of wind direction caused by temperature differences between the land and sea breeze, creating zones of high and low pressure over land in different seasons.
§ Monsoons occur due to changes in atmospheric pressure which are caused by different rates of heating and cooling of continents and oceans.
§ Monsoons occur every year in many countries around the world
§ The global surface monsoons contains three kinds of monsoons:
§ Tropical monsoon
§ Subtropical monsoon
§ Temperate-frigid monsoons
MONSOON ROUTE…
— The mountains of southern India split the summer winds. The western arm of the monsoon is deflected northwards, by the western Ghats, to Mumbai and then on to Pakistan.
— The eastern arm travels up through the Bay of Bengal to Kolkata and Assam, and is deflected north-westwards by the Himalayas.
— On average, the winds arrive in southern India about six weeks before they arrive in north-west India.
— The desert and adjoining areas of the northern and central Indian Subcontinent heats up too much during summer.
— This causes a low pressure area over the northern and central Indian subcontinent. To fill up this void, the moisture-laden winds from the Indian Ocean rush in to the subcontinent.
— These winds, rich in moisture, are drawn towards the Himalayas, creating winds blowing storm clouds towards the subcontinent.
— The southwest monsoon is generally expected to begin around the middle of June and dies down by September.
IT’S EFFECT
— There is a competition between zonal circulation and monsoon winds. We have to find which will be favored by global warming.
— Overall, global warming will change conditions in the sea more slowly than conditions on land, because of the difference in the rate of response to heating, a concept familiar from the sea breeze.
— Thus, we would expect the summer monsoons to be amplified by stronger warming in summer. In addition, with more moisture in the air, extracted from a warming ocean, rainfall (and flooding) might be expected to increase.
— Conversely, in winter, we should expect less of a difference, as the land refuses to get quite as cold as previously. So, the winter monsoons should weaken, as should any of the nutrient-supplying coastal upwelling associated with winter monsoons.
— Changes to India's annual monsoon are expected to result in severe droughts and intense flooding in parts of India.
— Scientists predict that by the end of the century the country will experience a 3 to 5 degree C temperature increase and a 20% rise in all summer monsoon rainfall.
— Climate change studies undertaken so far reveal that action is essential in order to prevent long term damage to India's water cycle.
— The livelihood of a vast population in India depends on agriculture, forestry, wetlands and fisheries and land use in these areas is strongly influenced by water-based ecosystems that depend on monsoon rains.
— India is already vulnerable to variations in the monsoon, both from year-to-year and within the season.
— One of the key questions in climate change is whether the remarkable stability of the monsoon rains will continue, or whether the monsoon will become more volatile.
— Most models predict a modest increase in inter annual variability but to differing degrees. At the heart of this are the projections of what will happen to El Nino - whether it will become stronger and/or more frequent - since El Nino has dominant influence on monsoon variability.
— Monsoon is important and scientists are engaged in understanding the variability of monsoon using observed data and numerical models.
— Hope that in future we will have more accurate prediction of Indian monsoon rainfall.
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