Lesson 10: Disaster Management

In the figure : In the figure famine has two groups of causes. Natural causes: drought, floods and locusts. Man-made causes: war, internal unrest and poor transport.

Rule 1: Causes of famine — Natural causes: drought (the main one), heavy rain and floods, damaged crops, weather changes (storms, cold waves, fog), rats, pests, locusts, crop diseases, earthquake. Man-made causes: war, internal unrest, lack of transport routes and uncontrolled population growth.

• Easy : Drought is the main natural cause of famine.
• Medium : Locusts eating the crops is a natural cause; war that stops food reaching people is a man-made cause.
• Exam-type : A village gets 700 mm rain normally but only 350 mm this year, a shortfall of 700 − 350 = 350 mm, which is half. Drought can lead to famine.

In the figure : In the figure the rain in one village in five years was 820, 760, 540, 310 and 380 mm. In Year 4 the rain was very low (310 mm), and drought can lead to famine.

Rule 2: Famine in history — Asia is the most famine-affected continent; the most dreadful famines affected India and China. Problems of drinking water, food and fodder date back to historic times. Chhatrapati Shivaji Maharaj and Chhatrapati Shahu Maharaj implemented schemes against famine. Malik Ambar made a canal scheme for drinking water in Aurangabad that exists even today.

• Easy : Malik Ambar's canal scheme in Aurangabad exists even today.
• Medium : Rain in Year 4 compared with Year 1: 820 − 310 = 510 mm less.
• Exam-type : Average rain of the five years = (820 + 760 + 540 + 310 + 380) ÷ 5 = 2810 ÷ 5 = 562 mm.

Spot the difference

In the figure : In the figure the very hot land (A) vapourises the falling rain, the vapour goes back up (B) into the cloud, and rapid condensation then gives heavy rain over a small region (C).

Rule 1: How a cloudburst happens — Because of very high temperature near the land, rain water vapourises and goes back into the clouds. The vapour in the clouds becomes very high, and by rapid condensation it rains suddenly over a small region.

• Easy : 100 mm in 1 hour is a cloudburst.
• Medium : 60 mm in half an hour = 120 mm per hour, which is more than 100 mm per hour, so it is a cloudburst rate.
• Exam-type : Mumbai on 26 August 2005 got about 950 mm in 8 to 10 hours: 950 ÷ 10 = 95 mm per hour at least, and 950 ÷ 8 ≈ 119 mm per hour at most.

In the figure : In the figure the rain in each hour of a storm was 8, 14, 112, 126, 20 and 6 mm, with a line at 100 mm. Hours 3 and 4 are cloudburst hours because they are above the line.

Rule 2: Human role and measures — We are responsible too: the balance between rainfall and population is disturbed; after the green revolution the balance of the environment was lost due to chemical fertilizers, pesticides and weedicides; there is unlimited lifting of water, erosion of land and misuse of water. To ease famine: use and reuse water in a planned way, plan water conservation and harvesting at the local level, plant trees on a large scale, stop deforestation and change plans according to weather forecasts.

• Easy : Planting trees on a large scale helps against famine.
• Medium : Rainwater harvesting at the local level stores water for dry months.
• Exam-type : Leh (Ladakh) had a cloudburst on 6 August 2010, five years after Mumbai's in 2005 (2010 − 2005 = 5).

Spot the difference

In the figure : In the figure flood protection is shown by new forests (A), a small dam in the hills (B) and a percolation tank (C). D is the river near the town.

Rule 1: Flood control — The Government of India set up the National Flood Commission in 1976; flood control plans are kept ready from the national to the village level. Protective measures: small dams in mountainous regions, percolation tanks, making river beds flat, cultivation of new forests and connecting rivers.

• Easy : New forests slow the rain water and reduce floods.
• Medium : Small dams in hills hold back water; percolation tanks let it sink into the ground.
• Exam-type : The Commission was set up in 1976, so by 2026 it is 2026 − 1976 = 50 years old.

In the figure : In the figure lightning occurs within one cloud (P), between two clouds (Q) or between a cloud and the ground (R).

In the figure : In the figure of 100 lightning flashes about 95 stay in the sky and only about 5 reach the ground.

Rule 2: About lightning — About 95% of flashes stay in the sky and 5% reach the ground. About forty flashes occur per second. The temperature is higher than that of the sun, so the air expands suddenly and a loud crash is heard. Lightning strikes open ground more than a tree or water, and mishaps occur at a high place or near a tall object. Survivors may suffer long-term effects, and immediate treatment can save life.

• Easy : 5% of flashes reach the ground, 95% stay in the sky.
• Medium : Out of 200 flashes, 5% × 200 = 10 reach the ground and 190 stay in the sky.
• Exam-type : About 40 flashes per second means 40 × 10 = 400 flashes in 10 seconds.

In the figure : In the figure four people in a thunderstorm stand 15 ft apart. The first and the last are 3 × 15 = 45 ft apart.

Rule 3: Precautions in a thunderstorm — Do not stand on open ground, below a tree, near a pole or tower, or lean on a wire fence. Get off a two-wheeler, bicycle, tractor or boat. Do not gather together; keep 15 feet between persons. Do not use plugged-in appliances, a mobile or a telephone. Stand on dry wood, plastic sheet or jute. Crouch low with feet together. Swimmers and fishermen should come out of the water. A pucca house is the safest place; fit a lightning conductor if necessary.

• Easy : Do not stand under a tree during lightning.
• Medium : Keep 15 ft between persons. For 6 persons in a row there are 5 gaps, so the first and last are 5 × 15 = 75 ft apart.
• Exam-type : In the open, crouch low with your feet together; a pucca house with a lightning conductor is safest.

In the figure : In the figure: do not stand under a tree (P). In the open, crouch low with your feet together (Q). A pucca house with a lightning conductor (R) is the safest place.

Spot the difference

In the figure : In the figure of a volcano molten rock rises from the magma chamber (E) through the vent (D) and comes out of the crater (B) as lava (C), with ash and gases (A).

Rule 1: Volcano — Lava, vapour, hot mud and sulphur collect and create mountains and hills. Ash and gases pollute the atmosphere, it often rains, temperature rises, and forests and settlements are buried under hot mud. Volcanoes erupt in the sea too and create islands. An eruption cannot be prevented, stopped or controlled, but science and technology can predict it.

• Easy : Lava flowing out of the crater is part of an eruption.
• Medium : A volcano erupting in the sea can create an island.
• Exam-type : An eruption cannot be stopped, so prediction and early warning matter.

In the figure : In the figure an earthquake on the sea floor (A) makes waves that are low but travel at 800 to 900 km per hour (B). Near the coast they slow down and rise up to about 30 m (C). The 1600 km here is a sample distance.

Rule 2: Tsunami — The waves are not very high near the source but spread at 800 to 900 km per hour. Near the coast the speed falls but the height rises up to about 30 metres. Tsunami is a Japanese word meaning 'harbour wave'. It destroys buildings, boats and ships, uproots trees, causes landslides and damages harbours and sea-related business. An artificial geostationary satellite helps to warn people of the coastal area.

• Easy : 'Tsunami' means 'harbour wave' in Japanese.
• Medium : A wave at 800 km per hour covers 2400 km in 2400 ÷ 800 = 3 hours.
• Exam-type : At 900 km per hour, 1800 km takes 1800 ÷ 900 = 2 hours, so a satellite warning gives people time to leave the coast.

Spot the difference

In the figure : In the figure of a storm: cut branches likely to fall (P), shut the gas valve (Q), turn off the electric supply (R) and phone relatives and friends (S).

Rule 1: In a storm — Regularly cut trees or branches likely to fall. If outside, take shelter in a safer place. Tell close relatives and friends your exact location. At home, shut the gas regulator valves and turn off the electric supply. Phone relatives and friends to warn them. Give temporary shelter to people far from home.

• Easy : Turn off the electric supply at home during a storm.
• Medium : Shut the gas regulator and phone relatives to warn them.
• Exam-type : A neighbour is stuck far from home during a storm; giving temporary shelter is a way of helping.

In the figure : In the figure a timeline shows some dates: UNDP set up in 1965, National Flood Commission in 1976, Mumbai cloudburst in 2005 and Leh cloudburst in 2010.

Rule 2: Institutions — The United Nations set up the standing international organisation UNDP in 1965; about 177 nations are members. It sends equipment, financial aid and volunteers to the place of disaster, along with international medical teams and groups of experts. 13th October is the International Day for Disaster Reduction. The website www.ndma.gov.in gives information about disasters and disaster management.

• Easy : 13th October is the International Day for Disaster Reduction.
• Medium : UNDP was set up in 1965 and the National Flood Commission in 1976: 1976 − 1965 = 11 years later.
• Exam-type : UNDP (1965) is 2026 − 1965 = 61 years old in 2026.

Spot the difference