Important Questions: Natural Hazards & Disasters | Geography Class 11 - Humanities/Arts PDF Download

Very Short Answer Type Questions

Q1: Name some common natural hazards.
Ans: Some common natural hazards are volcanic eruptions, earthquakes, droughts, floods, cyclones arid soil erosion.

Q2: What are the causes of human-induced hazards?
Ans: The human-induced hazards are caused by human activities such as a nuclear explosion, fire, industrial, etc.

Q3: How are the earthquakes of non-tectonic origin caused?
Ans: By volcanic eruptions, rock-bursts, subsidence in mines, impounding of reservoirs, etc.

Q4: How does flood occur?
Ans: The flood occurs when a river overflows its banks and spreads out over the plains.

Q5: Which months experience the maximum number of storms in the Bay of Bengal and the Arabian Sea?
Ans: October and November.

Q6: What is a flash flood?
Ans: It is a sudden violent flood caused by exceptionally heavy rain in a normally dry valley in a semi-arid area.

Q7: Identify two forms of landslides.
Ans: Translational and rotational.

Q8: What are avalanches?
Ans: A large mass of snow mixed with earth, stones, and ice loosened from a mountainside and drawn swiftly by gravity to the valley is called avalanche.

Short Answer Type Questions

Q9: Name a high and very high-risk seismic area of India.
Ans: From the earthquake point of view, the high-risk areas are the Ganga plains and western Rajasthan, whereas the very high-risk areas are the Himalayan mountain, north-eastern India, Kachchh, west coast around Ratnagiri and Andaman and Nicobar islands.

Q10: What is the velocity of a cyclone and its normal duration?
Ans: The speed of movement of a cyclone per unit of time is called its velocity. The cyclones move at an average velocity of about 20 km. per hour. Its normal duration is five to seven days.

Q11: Name two human activities that cause a flood in India.
Ans: These are the two factors that increase the incidence of a flood.

• Deforestation,
• Drainage congestion (caused by the badly planned construction of bridges, roads, railway tracks, and other developmental activities).

Q12: What is disaster management?
Ans: The term disaster management includes all aspects of prevention and protection measures, preparedness, and organization of relief operations for mitigating the impact of disasters on human beings and socio-economic aspects of the disaster-prone area.

Q13: What are the major hazards that occur in India?
Ans: Drought, floods, cyclones, landslides, and earthquakes are some of the major hazards which occur in India. These natural hazards or disasters are the results of sudden earth movements that change the face of the earth in a short period causing heavy loss of life and property.

Q14: Define solifluction.
Ans: Solifluction is the slow movement of rock debris, saturated with water and not confined to definite demands, down a slope under the force of gravity. It occurs particularly when thawing releases such surface deposits while the underlying layers are still frozen. The term is usually applied to saturated deposits.

Long Answer Type Questions

Q15: What should people do and don’t do in an area going to be hit by a cyclone?
Ans: In order to draw the attention of the people of the world, the UNESCO observed International Decade for natural disaster Reduction during 1990-2000. Along with other nations of the world, India observed World Disaster Reduction Day in October during the decade. Do’s and Don’ts for the people in cyclone-hit areas, which were issued by the Government of India are as follows:

• Listen to the radio for advance information and advice. Allow a considerable margin for safety.
• When the storm force winds or severe gales are forecast for your area: store or secure loose boards, corrugated iron, rubbish lines, or anything else that could become dangerous; tape up large windows to prevent them from shattering; and move to the nearest shelter or evacuate the area if this is ordered by the ‘ appropriate government agency.
• When the storm hits it is advisable: to stay indoors and take shelter in the strongest part of your house; listen to the radio and follow instructions; open windows on the sheltered side of the house if the roof begins to lift; find shelter if you are caught out in the open, and do not go outside during a lull in the storm.

Q16: What is a tsunami? How it occurs and what are its consequences? Describe in detail.
Ans: A tsunami is a series of waves generated in the body of water by an impulsive disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, and even the impact of cosmic bodies such as asteroids can generate a tsunami. When the Indian plate in the north-east gets locked with the Eurasian plate, it creates high stress, and the accumulation of high energy causes an earthquake.

• Cause: Nomially the seismic waves cause only one instantaneous vertical wave but after the initial disturbance, a series of after waves are created in the water that oscillates between the high crest and low trough in order to restore the water level. The speed of waves in the ocean depends upon the depth of water. It is more in shallow water than at the ocean depth.
• Consequences: The impact of the tsunami is less over the ocean and more near the coast where they cause large scale devastation. Therefore, a ship at sea is not much affected by tsunamis. The tsunami wave raises the ship only one meter because over deep water tsunami has a very long wavelength and limited wave height. Over shallow water, tsunami causes large-scale destruction along the shores, here wavelength gets reduced and height can be up to 15 meters.

After reaching the coast they release enormous energy and destroy the port cities and towns, structures, buildings, and other settlements. The loss of property’ and life by the tsunami is much higher as compared to other natural hazards in the coastal areas.

• Mitigation steps: It is difficult to mitigate the hazards caused by the tsunami because of the fact that losses are on a much large scale.

Q17: Discuss the three components of the impact phase of disaster management.
Ans: The term disaster management includes all aspects of preventive and perspective measures, preparedness, and organization of relief operations for mitigation of the impact of the disaster on human beings and socio-economic aspects of the disaster-prone areas.-The whole process of disaster management can be divided into three phases, impact phase, rehabilitation and reconstruction phase, and integrated large term development and preparative phase.
The impact phase contains three components – forecasting of disaster, close monitoring of agents causing disasters, and management activities after the disaster has occurred. As far as forecasting of disaster is concerned, flood forecasting can be done by studying rainfall in the catchment area. The approach of cyclones can be tracked and monitored by satellites. Based on these details, early warning and evacuation efforts may be made.
Close monitoring of agents responsible for disaster can help the deployment of terms to help evacuation and supply of food clothing and drinking water. Disaster leaves a trail of death and destruction. This will require medical care and the help of the affected people. Under the long-term development phase, preventive and precautionary measures of various kinds should be chalked out.

Q18: Describe the flood in India as a disaster. Write an essay on floods as a disaster.
Ans: Floods are a major cause of human misery in India every year. Out of a number of natural disasters that the country has experienced, floods are the most important ones. India is the most flood-affected country in the world next to Bangladesh. Twenty percent of the global deaths caused by floods in the world are in India.
In spite of the fact that floods are a natural disaster, it often turns out to be a social disaster as the people who are severely affected are generally the poor because they live on the periphery of the human habitat. The annual flood-affected population has arisen faster than the growth of India’s population. The flood-affected area and damages have also increased recently; the reason for this increase is the encroachment of floodplains by the people.
The most flood-prone basins in the country are those of the Ganga in Uttar Pradesh, Bihar, and West Bengal, the Brahmaputra in Assam, and the Batumi, the Brahmani, and the Subarnrekha basins in Orissa. Sometimes floods occur also in Andhra Pradesh, Rajasthan, Haryana, and Gujarat.

• Flood Control: Floods are not new in India. The practice of building flood protection embankments along rivers is an ancient one. We had flood protection embankments on the Godavari, Krishna, and the Kaveri deltas and in the Indo-Ganga plain.

The nationwide flood protection programs, however, began only after independence. At the time of independence in 1947, India had some 5280 km. of embankments along different rivers. Of this 3500 km. were in the Sundarbans in the West Bengal and 1209 km. along the Mahanadi in Orissa. This provided protection to about 3 million hectares of land.
In 1954 a spate of severe floods came. Enormous devastation was caused in Uttar Pradesh, Bihar, West Bengal, and Assam. Long term programs for the construction of dams and embankments were drawn. Central and state flood control boards were set up. In spite of various measures taken up to minimize the fury of floods, they are still a regular feature in the Ganga and the Brahmaputra basin. Reducing Impact of Flood-The building of embankments was the only way floods could be controlled in the forties.

The dams and reservoirs were considered useful to control runoff water and reduce flooding. Now there are several other measures to reduce the severity of the flood. The felling of trees and deforestation on mountain slopes and in catchment areas need control. Weather forecasts and flood warnings are a regular feature.

Q19: What do you understand by ‘tsunami’?
Ans: A tsunami is a series of large ocean waves with very long wavelengths (typically hundreds of kilometers) caused by large-scale disturbances of the ocean, such as volcanic eruptions, landslides, or most commonly, underwater earthquakes. The word "tsunami" comes from the Japanese words "tsu" (meaning harbor) and "nami" (meaning wave). Tsunamis can travel across entire ocean basins and can move as fast as a jet plane, reaching speeds of up to 700 kilometers per hour (500 miles per hour) in deep water.
Tsunamis are usually imperceptible in the open ocean because of their long wavelengths and low wave amplitudes. However, as they approach shallower coastal waters, the waves slow down and their amplitudes increase dramatically. This causes tsunamis to transform into massive, fast-moving walls of water that can inundate coastlines, causing widespread destruction. When a tsunami reaches the coast, it can cause severe flooding, extensive property damage, and loss of life. The impact of a tsunami on coastal communities can be devastating, with waves sweeping far inland, and destroying buildings, infrastructure, and natural habitats.
Early warning systems and education efforts are in place in many coastal regions to mitigate the impact of tsunamis. These systems aim to detect seismic activity and issue warnings to vulnerable areas, giving people time to evacuate and take necessary precautions before the tsunami waves arrive. Despite these efforts, tsunamis remain a significant natural hazard, requiring ongoing research and preparedness measures to minimize their impact on coastal populations.

Q20: How do embankments worsen the problem of a flood?
Ans: Embankments, also known as levees or dikes, are human-made structures built along riverbanks or coastlines to prevent flooding by containing the flow of water within a specific area. While these structures are intended to protect against flooding, they can sometimes worsen the problem in several ways:

• Increased Severity of Flooding: Embankments can create a false sense of security among residents, encouraging them to build settlements and infrastructure in flood-prone areas behind the embankments. When a breach occurs or the embankment overtops during a severe flood event, the flooding that results can be more severe and widespread than if the embankment were not present.
• Erosion and Sedimentation: Embankments can cause increased erosion and sedimentation downstream. When water is funneled quickly through a narrow channel created by embankments, it gains significant erosive power. This erosive force can lead to the degradation of riverbanks downstream and increase sedimentation, altering the natural flow of rivers and exacerbating flood risks.
• Lateral Channel Shifting: Embankments restrict the natural lateral movement of rivers. As a result, rivers are not allowed to shift laterally over time, a natural process that helps dissipate energy during flood events. This lack of lateral movement can lead to increased erosion on one bank and excessive sediment deposition on the other, changing the river's course and potentially causing more severe flooding downstream.
• Maintenance Issues: Embankments require regular maintenance to ensure their structural integrity. If not properly maintained, they can weaken over time, making them susceptible to breaches or failures during heavy rainfall or high-water events. Poor maintenance can render embankments ineffective in flood protection, leaving areas vulnerable to flooding.
• Alteration of Natural Drainage Patterns: Embankments can disrupt natural drainage patterns, leading to waterlogging in areas that were previously well-drained. This alteration of drainage patterns can create new flood-prone areas where water collects but cannot efficiently drain away.
• Displacement of Flooding: By protecting one area with embankments, flooding can be displaced to downstream or adjacent areas that are not protected. This can result in increased flood risks for communities located in these downstream areas, leading to a cascading effect of flood-related issues.

To effectively manage flood risks, it's essential to implement comprehensive flood management strategies that consider the natural dynamics of river systems, involve community participation, and employ a combination of structural and non-structural measures tailored to the specific needs of the region. Simply relying on embankments without considering their long-term and downstream impacts can exacerbate rather than alleviate the problem of flooding.