NIOS Class 12 Environmental Science Chapter 12 Disasters And Their Management

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NIOS Class 12 Environmental Science Chapter 12 Disasters And Their Management

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Disasters And Their Management

Chapter: 12

Module 4: Contemporary Environment issues

Textual Question Answer

INTEXT QUESTIONS 12.1

1. Define: (i) Floods (ii) Earthquake (iii) Cyclone (iv) Tsunami.

Ans: (i) Floods are temporary inundation of a large region as a result of increase in level of river or reservoir.

(ii) Earthquake is a sudden release of energy accumulated in defamed rocks of earth crust causing the ground to tremble or shake.

(iii) Cyclones are wild storms often of vast extent, characterised by strong and high winds rotating about a calm centre of low atmospheric pressure.

(iv) Tsunami is a catastrophic ocean wave, caused by a submarine earthquake.

2. Mention two ways by which floods may be controlled.

Ans: Through afforestation and construction of dams.

3. State any one effect of tsunami.

Ans: Sea water floods the land and wash away human settlement, agriculture and other properties.

4. Why is a cyclone, generally, followed by floods?

Ans: Due to heavy rain causes flood and vulnerable form of flood is followed by cyclone.

5. State the change in the ocean with predicts the event of tsunami. 

Ans: In the tsunami, the waves of simple, progressive oscillatory waves spread to great distances on the surface of the ocean in ever-widening circles, much like the waves created by a pebble dropping into a shallow lake. This discovery helps seismologists to forecast the arrival of the tsunami.

INTEXT QUESTIONS 12.2

1. Name three disasters caused by human carelessness.

Ans: Fires, Accidents (rail, road, air), industrial accidents.

2. How can road accidents be prevented? 

Ans: Drive safely, lane driving by following traffic rules, any other.

3. Why should chemicals be stored away from human settlements?

Ans: To prevent industrial accidents.

4. State two causes of disasters fire? 

Ans: (i) To throw burning match sticks or cigarettes.

(ii) Short circuit of electric wires.

5. Why are diseases such as HIV/AIDS considered as a disaster? 

Ans: Because it affects a large number of population.

INTEXT QUESTIONS 12.3

1. Name the form components of disaster management.

Ans: Preparedness, response, recovery, prevention.

2. Why is community level disaster management important? 

Ans: Because the community or neighbours respond first to disaster situation.

3. Define NCDM?

Ans: National Committee on Disaster Management (NCDM) has set up by Government of India under the chairmanship of the prime minister.

TERMINAL EXERCISE

1. Why do floods occur?

Ans: Causes of the flood:

(i) Floods are caused by rains, high winds, cyclones, tsunami, melting snow, or dam burst.

(ii) A flood can happen gradually or can happen unexpectedly due to heavy rains, breach of the water storage and control structures, and spill over.

(iii) Siltation of the rivers and reservoirs and can enhance the frequency and severity of floods.

2. How can you mitigate the effects of floods?

Ans: A flood can be controlled in various ways:

Flood water can be minimized by reducing the flow of water by afforestation. Forests facilitate rainwater percolation in the soil, thus recharging groundwater and minimizing runoff.

The building of dams further decreases the volume of flood water by storage. Dams can hold water that cannot be housed in the downstream channel, which can cause flooding. Water can be discharged from the dam in a controlled manner.

3. Why is drought common in our country?

Ans: Drought is a phenomenon that occurs from less than average predicted rainfall over a season or period of time. Low rainfall is inadequate to satisfy the needs of humans, trees, livestock, and agriculture. Short rainfall resulting in the drying of rivers, dams, reservoirs, and the drying of wells due to excessive withdrawal and low recharge of groundwater, and lack of crop production due to water scarcity are some of the key indicators of drought. 

When rainfall is insufficient by more than 10% of the normal annual rainfall, the situation induces drought. In recent history, drought cycles have intensified due to deforestation and environmental destruction.

4. How can the ill effects of drought overcome?

Ans: The adverse effects of drought can be minimized if some measures are taken:

(i) Daily tracking of runoff, water supply in ponds, dams, and waterways, as well as in relation to demand.

(ii) As water supply reduces relative to demand, water use needs to be decreased by the implementation of various water-saving steps. This includes saving water use, increasing the quality of water usage, reducing pollution, and reusing wastewater for inferior purposes. 

(iii) Any essential steps to alleviate the drought are the use of effective irrigation methods and the sowing of low water-consuming crops.

(iv) Rainwater mining enhances the supply of water. Water recycling shall be carried out either by allowing run-off water from all catchment areas to a common point and by storing it in a reservoir or by allowing it to percolate into the land so far by recharging groundwater.

5. What is tsunami?

Ans: Tsunami is a sequence of large waves caused by disturbances in the sea bed. A tsunami is also known as the seismic sea wave, or tidal wave, a devastating ocean flood, typically caused by an underwater shake less than 50 km (30 miles) below the seafloor, with a magnitude greater than 6.5 on the Richter scale. Underwater or coastal landslides or volcanic eruptions can also cause a tsunami.

6. Why do epidemics occur in our country?

Ans: Causes of the epidemic:

(i) The incidence of diseases is primarily due to inadequate sanitary conditions contributing to water pollution or the spread of disease through the breeding of disease vectors.

(ii) Other considerations include seasonal changes that benefit insect breeding. Vectors, exposure to non-immune communities (e.g., visitors or migrants), insecurity, and overcrowding.

7. Write a note on fire mitigation measures.

Ans: Certain measures for fire:

(i) Obey fire safety rules and remember the evacuation route in case of fire.

(ii) Keep and handle inflammable materials with utmost care. 

(iii) Keep a fire extinguisher in the house and learn how to use it. 

(iv) When you leave home, make sure to shut off all electrical and gas appliances.

(v) Do not plug several devices into one socket.

(vi) Keep matches away from children.

(vii) Do not block access routes by cupboards or any furniture.

(viii) In the event of a fire call the fire department immediately

8. Give a brief account of damage caused by industrial accident.

Ans: Industrial plants and close vicinity are at high risk in the event of an industrial accident. Employees and residents of surrounding towns and their cattle and crops in adjacent areas are badly impacted. The air over a large field is being poisoned. Hazardous contaminants released into the air or water can migrate long distances and can also kill the whole ecosystem surrounding the manufacturing area. Explosion or fire or leakage of corrosive materials badly damages houses. If the chemical is in a gaseous state, the geographical spread is rapid and broad. Many people can die either as a result of the mechanical explosion or fire damage or as a result of toxic chemicals. Inhalation, eye exposure, skin contact, and absorption are the processes of response to the chemical resulting from injuries.

9. What are the advantages of involving the community in disaster management?

Ans: Community-level participation in disaster management is very useful as they are the first responders. If proper mass awareness programs are conducted for the people, a majority of disasters can be avoided.

The first few hours before and after a disaster are critical and precious for saving lives and reducing further injury.

Often external help may take time to reach the disaster site. In any disaster, often the neighbors are first to respond.

The first responders are people who act first in a disaster situation, usually lack basic response skills to deal with medical or other emergencies.

The aim of community-level management is to train the individuals and the members of the local community to deal with the emergency situation effectively. Trained community members are lifesaving assets in such situations. Thus, community-level management involves people’s participation.

10. What is the contribution of the government in disaster management?

Ans: NCDM is the National Committee on Disaster Management set up by the government of India under the chairmanship of the prime minister. The recommendations of this National Committee would form the basis of the national disaster risk management program and strengthening the natural disaster management and response mechanisms.