NIOS Class 12 Environmental Science Chapter 12
INTEXT QUESTIONS 12.1
1. Define: (i) Floods, (ii) Earthquake, (iii) Cyclone, (iv) Tsunami
Ans:
- (i)Are temporary inundations of a large region as a result of an increase in the level of the river or reservoir.
- (ii) Is a sudden release of energy accumulated in the deep rocks of Earth’s crust causing the ground to tremble or shake.
- (iii) Are wild storms often of vast extent, characterized by strong and high winds rotating about a calm centre of low atmospheric pressure.
- (iv) Is a catastrophic ocean wave, caused by a submarine earthquake.
2. Mention two ways by which floods may be controlled.
Ans: Flood control can be achieved through various means.
- The floodwater can be reduced by reducing the run-off water through afforestation.
- Forests promote rainwater percolation in the ground, thus recharging the groundwater and reducing the runoff water.
- The construction of dams also reduces floodwater through storage. Dams can store water, which can not be accommodated in the river downstream, and may cause floods. Water can be released in a controlled manner from the dam.
- Desilting, deepening, and increasing embankment increase the capacity of a river/channel/drain.
3. State any one effect of tsunami.
Ans: The effects of tsunamis are quite similar to those of cyclones or floods. Huge waves of seawater enter with great force and flood the land and washing away human settlements, agricultural crops and other properties.
4. Why is a cyclone generally followed by floods?
Ans: Cyclone is generally followed by heavy rains, causing floods. Due to heavy rains, people and their property might be washed away in floods or blown away by the cyclone itself. The cyclone along the coastal areas may cause sea waves to enter on land and flood it.
5. State the change in the ocean with predicts the advent of tsunami.
Ans: In a tsunami, a train of simple, progressive oscillatory waves is propagated to great distances at the ocean surface in ever-widening circles, much like the waves produced by a pebble falling into a shallow pool. The observation has enormous practical value, enabling seismologists to issue warnings to endangered coasts immediately after an earthquake and several hours before 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: To avoid accidents following safety measures can be adopted:
- Look on either side of the road before crossing.
- Use a zebra crossing while crossing the road on foot.
- Wear a helmet while riding a two-wheeler.
- Use the seat belt provided in your car.
- Drive only if you possess a proper driving license.
- Be familiar with road markings and honour them.
- Maintain a safe distance from the vehicle in front.
- Do not jump lanes. It becomes difficult for other vehicles on the road to anticipate your move.
- Do not be rash and do not try to overtake unnecessarily.
- The best way to be safe on roads is to follow “lane driving”.
- While driving, avoid sudden acceleration and deceleration.
- Replace the worn tyres and faulty headlamps.
- Check the tyre pressure, radiator water, brake oil and fuel frequently.
- Dip your beam whenever you spot an oncoming vehicle.
- Follow the maintenance schedule prescribed by the manufacturer.
- Overcome impatience, anger and intoxication during driving. Road rage is dangerous.
3. Why should chemicals be stored away from human settlements?
Ans: To prevent industrial accidents
4. State two causes of disasters fire?
Ans: There are numerous causes of fires. Some important ones are given here-
- Throwing burning matchsticks or cigarettes irresponsibly.
- Heating sources can cause fire in houses, e.g. clothes may catch fire while cooking on a kerosene stove or a gas stove.
- Cooking accidents are a major cause of fire at home. Fire can result from unattended cooking.
- A short circuit in an electrical wiring can cause a fire. Overheating of electric appliances, poor wiring connections, use of sub-standard quality appliances can also result in a fire.
- Rubbish and waste materials often lying on roadsides or near houses may catch fire when people throw burning matchsticks or cigarette butt.
- Storage and transportation of inflammable material or explosive chemicals without proper precautions may cause fires.
- Forest fires may result from human negligence or carelessness.
5. Why are diseases such as HIV/AIDS considered as a disaster?
Ans: Diseases such as HIV/AIDS are considered a disaster because they affect a large portion of the population.
INTEXT QUESTIONS 12.3
1. Name the form components of disaster management.
Ans: Prepareness, response, recovery, and prevention.
2. Why is community-level disaster management important?
Ans: Community-level disaster management is important because, in any disaster, often the neighbours are first to respond. The first responders are people who act first in a disaster situation, and usually lack basic response skills to deal with medical or other emergencies.
3. Define NCDM?
Ans: The National Committee on Disaster Management (NCDM) was set up by the Government of India under the chairmanship of the Prime Minister.
TERMINAL EXERCISE
1. Why do floods occur?
Ans: Floods are caused by rain, high winds, cyclones, tsunamis, melting snow or a dam burst. Flood can happen gradually or can happen suddenly due to heavy rains, breach of the water storage and control structures, or spillover. Siltation of the rivers and reservoirs can enhance the incidence and magnitude of floods.
2. How can you mitigate the effects of floods?
Ans: Flood control can be achieved through various means.
- The floodwater can be reduced by reducing the run-off water through afforestation.
- Forests promote rainwater percolation in the ground, thus recharging the groundwater and reducing the run-off water.
- The construction of dams also reduces floodwater through storage. Dams can store water, which can not be accommodated in the river downstream, and may cause floods. Water can be released in a controlled manner from the dam.
- Desilting, deepening, and increasing embankment increase the capacity of a river/channel/drain.
- Normally, there is a reasonable, timely warning by alerting people and moving them to a safer area well in time.
- Measurement of the intensity of rainfall in the catchment area provides a sufficient clue to hydrology engineers to calculate the possible submergence area along a river well before the flooding occurs. Accordingly, expected run-off volume, people can be warned to evacuate the likely areas to be flooded and advised to go to safer places along with their belongings, including livestock.
3. Why is drought common in our country?
Ans: Drought occurs due to a shortage of rainfall. As per the Meteorological Department, if rainfall is deficient by more than 10% of the annual average rainfall, the condition is said to be that of drought. The severity of drought is determined by the extent of deviation of rainfall from the average. In the recent past frequency of periods of drought has increased due to deforestation and environmental degradation.
4. How can the ill effects of drought be overcome?
Ans: The adverse effects of drought can be minimized if some measures are taken.
- A regular monitoring of rainfall, water availability in reservoirs, lakes and rivers, as well as in comparison it with the demand.
- When water availability decreases below demand, water consumption needs to be reduced by adopting various water conservation measures. These include economizing water consumption by increasing water use efficiency, reducing wastage, and reusing the wastewater for non-potable uses.
- The use of efficient methods of irrigation and sowing low water-consuming crops is one important measure to overcome drought. Rainwater harvesting increases water availability.
- Water harvesting is done by either allowing the run-off water from all the catchment areas to a common point and storing it in a reservoir, or allowing it to percolate into the ground so thus recharging groundwater.
5. What is tsunami?
Ans: Tsunami is also called a seismic sea wave, or tidal wave, a catastrophic ocean wave, usually caused by a submarine earthquake occurring less than 50 km (30 miles) beneath the seafloor, with a magnitude greater than 6.5 on the Richter scale.
6. Why do epidemics occur in our country?
Ans: The outbreak of diseases is mainly due to poor sanitary conditions, leading to contamination of water or spread of disease from breeding of the disease vectors. Other factors include seasonal changes that favour the breeding of insects. Vectors, exposure of a non-immune population (eg tourists or migrants), poverty and overcrowding.
7. Write a note on fire mitigation measures
Ans: Fire mitigation measures
- Obey fire safety rules and remember the evacuation route in case of fire.
- Keep and handle inflammable materials with utmost care.
- Keep a fire extinguisher in the house and learn how to use it.
- When you leave home, make sure to shut off all electrical and gas appliances.
- Do not plug several devices into one socket.
- Keep matches away from children.
- Do not block access routes by cupboards or any furniture.
- In the event of a fire, call the fire department immediately.
- In the smoke-filled corridor, crawl on all floors or on your belly as the smoke is less on the floor.
- Find at least two ways to escape from your home.
- Make sure that you remove all the waste material from the workplace and home regularly.
- Hazardous materials such as paints, solvents, adhesives, chemicals or gas cylinders should be kept in separate storage, well away from fire.
- Firecrackers on Diwali are a major cause of fire in our country. Use them carefully under the supervision of elders.
8. Give a brief account of damages caused by industrial accidents.
Ans:
- The industrial premises and immediate surroundings are at high risk in the event of an industrial accident.
- Employees and residents of nearby localities and their livestock and crops in nearby areas are severely affected.
- The environment over a large area gets polluted.
- Hazardous chemicals released into the atmosphere or into a water body may travel long distances and may even damage the entire ecosystem around the industrial area.
- Explosion or fire, or leakage of corrosive chemicals, can severely damage structures. If the chemical is in gaseous form, the geographical spread is fast and wide.
- Many people may die either due to mechanical damage from explosion or fire, or due to the toxicity of the poisonous chemicals.
- The polluting agents can have both immediate and long-term effects.
- The immediate effects include death or other symptoms like dizziness, headache, irritation, etc.
- The long-term effects may include cancer, heart failure, brain damage, dysfunction of the immune system, deformation, genetic disorders or congenital(by birth) disorders in children.
9. What are the advantages of involving the community in disaster management?
Ans: Community-level management aims to train the individuals and the members of the local community to deal with an emergency situation effectively. 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 neighbours are first to respond. The first responders are people who act first in a disaster situation, and usually lack basic response skills to deal with medical or other emergencies. Trained community members are life-saving assets in such situations. Thus, community-level management involves people’s participation.
10. What is the contribution of the government in disaster management?
Ans:
- Development of state and district disaster management plans.
- Development of disaster risk management and response plans at Village/ Ward, Gram Panchayat, Block/Urban Local Body levels.
- Constitutions of Disaster Management Teams and Committees at all levels with adequate representation of women in all committees and teams. (Village/ Ward, Gram Panchayat, Block/Urban local body, District and State.)
- Capacity Building of Disaster Management Teams at all levels. Special training for women in first aid, shelter management, water and sanitation, rescue and evacuation, etc.
- Capacity Building in cyclone and earthquake resistant features for houses in disaster-prone districts, training in retrofitting, and construction of technology demonstration units.
- Integration of disaster management plans with development plans of local self-governments.
