Chapter Notes

Natural Hazards and Disasters

Change is a fundamental law of nature, happening all around us continuously. Some changes are slow and gradual, like the formation of mountains, while others are sudden and swift, like earthquakes or volcanic eruptions.

From nature's point of view, these changes are neutral—neither good nor bad. However, from a human perspective, we assign values to them. We see the changing of seasons or the ripening of fruit as good, but we consider events like earthquakes, floods, and wars to be bad and undesirable because they cause harm and suffering. This chapter focuses on these "bad" changes, which we often call disasters.

What is a Disaster?

A disaster is a sudden, undesirable event, often caused by forces beyond human control, that strikes with little warning. It causes serious disruption to life and property, including death and injury to many people. The scale of a disaster is so large that it requires a response beyond what normal emergency services can provide.

For a long time, people viewed disasters as purely natural events, with humans as helpless victims. However, we now understand that human activities can also cause or worsen disasters.

• Direct Human-Caused Disasters: These are events directly caused by human actions. Examples include the Bhopal Gas tragedy, the Chernobyl nuclear disaster, wars, and environmental pollution.
• Indirect Human Impact: Sometimes, human actions don't directly cause a disaster but make a natural event much worse. For instance, deforestation can lead to more severe landslides and floods. Unscientific construction in fragile areas also increases the risk.

While it's possible to prevent some human-made disasters, preventing natural disasters is very difficult. Therefore, the focus has shifted to natural disaster mitigation and management—finding ways to reduce their impact and prepare for them.

Natural Hazards vs. Natural Disasters

People often use the terms "natural hazard" and "natural disaster" interchangeably, but they have distinct meanings.

• Natural Hazards are elements or circumstances in the natural environment that have the potential to cause harm to people or property. A steep, unstable slope in the Himalayas is a hazard; the potential for a landslide is always there.
• Natural Disasters are the actual events that cause large-scale, widespread death, loss of property, and social disruption. A hazard becomes a disaster when the event happens and its impact is severe.

Over time, the damage caused by natural disasters has increased. This is partly because technology has allowed humans to move into and develop disaster-prone areas, like building cities on coastlines vulnerable to tsunamis and cyclones. This increases our vulnerability, or our exposure to risk.

Recognizing that disasters are a global problem, the United Nations took action, leading to the World Conference on Disaster Management in May 1994 at Yokohama, Japan. This meeting produced the Yokohama Strategy, a global plan to make the world safer from disasters.

Classification of Natural Disasters

To deal with disasters effectively, it's helpful to classify them. Natural disasters can be broadly grouped into four categories:

• Atmospheric: Blizzards, thunderstorms, cyclones, drought, hailstorms, heat waves.
• Terrestrial: Earthquakes, volcanic eruptions, landslides, avalanches, soil erosion.
• Aquatic: Floods, tidal waves, storm surge, tsunami.
• Biological: Pests (like locusts), insect infestations, and diseases like bird flu or dengue.

India's vast size and diverse environment make it vulnerable to most of these disasters, which cause significant loss of life and property every year.

Yokohama Strategy and International Decade for Natural Disaster Reduction (IDNDR)

The World Conference on Natural Disaster Reduction in Yokohama, Japan (May 23rd-27th, 1994) acknowledged that the impact of natural disasters had grown, especially affecting poor and disadvantaged groups in developing countries. The conference adopted the Yokohama Strategy and Plan of Action for a Safer World to guide disaster mitigation efforts.

Key principles of the resolution include:

• Each country is responsible for protecting its own citizens.
• Priority attention should be given to developing countries.
• Countries should strengthen their own capabilities for disaster prevention and mitigation, involving non-governmental organizations and local communities.
• International cooperation should be promoted, focusing on capacity-building, technology sharing, and mobilizing resources.

The conference also declared the decade 1990-2000 as the International Decade for Natural Disaster Reduction (IDNDR).

Natural Disasters and Hazards in India

India's large geographical area, environmental diversity, large population, and history of social discrimination have increased its vulnerability to natural disasters. Let's look at some of the major disasters that affect the country.

Earthquakes

Earthquakes are among the most unpredictable and destructive of all natural disasters. Tectonic earthquakes, caused by the movement of the Earth's crust, are the most devastating.

Causes in India:

• The Indian plate is moving northwards at about one centimeter per year, constantly pushing against the Eurasian plate.
• This movement causes the plates to lock together, building up immense stress and energy.
• When this energy is suddenly released, it causes earthquakes along the Himalayan arch.
• This makes regions like Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, Sikkim, West Bengal (Darjeeling), and all northeastern states highly vulnerable.
• Severe earthquakes have also occurred in Peninsular India, specifically Gujarat and Maharashtra. Scientists believe a fault line may be emerging along the Bhima river, causing energy to build up in this traditionally stable landmass.

Earthquake Hazard Zones in India: Based on an analysis of over 1,200 past earthquakes, India has been divided into five zones. The two most critical are:

• Very High Damage Risk Zone: Includes the North-east states, parts of Bihar near the Indo-Nepal border, Uttarakhand, Western Himachal Pradesh, the Kashmir Valley, and the Kuchchh region of Gujarat.
• High Damage Risk Zone: Includes the rest of Jammu & Kashmir and Ladakh, Himachal Pradesh, northern Punjab, parts of Haryana, Delhi, Western Uttar Pradesh, and Northern Bihar.
• The rest of the country falls into moderate to very low-risk zones, with the stable Deccan plateau being one of the safest areas.

Socio-Environmental Consequences of Earthquakes

Earthquakes cause widespread destruction of settlements, infrastructure, and communication networks. They leave people homeless and put immense pressure on the economy, especially in developing countries.

Effects of Earthquakes:

• On the Ground: Fissures (cracks), landslides, liquefaction (where soil behaves like a liquid).
• On Man-made Structures: Cracking, sliding, overturning, and complete collapse.
• On Water: Formation of large waves, including devastating tsunamis.
• Environmental Consequences: Earthquakes can cause rivers to change their course, leading to floods, and create blockages that form new reservoirs.

Earthquake Hazard Mitigation

Since earthquakes cannot be prevented, the best approach is to focus on preparedness and mitigation.

1. Monitoring: Establish seismological centers to monitor earth movements and disseminate information quickly. Using GPS can help track tectonic plate movement.
2. Vulnerability Mapping: Create maps showing high-risk areas and educate the public on how to minimize the impact.
3. Improved Construction: Modify building designs in vulnerable areas. Discourage high-rise buildings and large industrial establishments in these zones.
4. Building Codes: Make it mandatory to use earthquake-resistant designs and light materials for construction in high-risk areas.

Tsunami

A tsunami (Japanese for "harbour wave") is a series of high vertical ocean waves caused by abrupt movements of the sea floor, usually from underwater earthquakes or volcanic eruptions.

After the initial disturbance, a series of waves are created that move across the ocean.

• In Deep Water: The waves have a very long wavelength and low height (perhaps only a meter or two), making them difficult to detect. A ship at sea might not even notice a tsunami passing.
• In Shallow Water: As the waves approach the coast, the water depth decreases. This causes the wavelength to shorten and the wave height to increase dramatically, sometimes up to 15 meters or more.

Tsunamis are frequent along the Pacific ring of fire, affecting countries like Japan, the Philippines, and Indonesia. After hitting the coast, they release enormous energy, destroying cities, towns, and settlements. Because coastal areas are often densely populated, the loss of life and property can be immense.

Tropical Cyclone

A tropical cyclone is an intense low-pressure system that forms over tropical oceans between 30° N and 30° S latitudes. It is like a giant heat engine, powered by the latent heat released when warm, moist air condenses.

Conditions for Formation:

• A large and continuous supply of warm, moist air.
• Strong Coriolis force to prevent the low pressure from filling in at the center (this is why cyclones don't form near the equator, from 0°-5° latitude).
• Unstable atmospheric conditions that create local disturbances.
• Absence of strong vertical wind shear, which would disrupt the storm's structure.

Spatio-temporal Distribution of Tropical Cyclone in India

In India, tropical cyclones originate in the Bay of Bengal and the Arabian Sea.

• Most cyclones in the Bay of Bengal develop during October and November.
• The location where they form shifts with the seasons, moving further north near the Sunderban Delta by July.

Consequences of Tropical Cyclones

The energy of a cyclone comes from warm ocean water, so its force decreases as it moves inland.

• Coastal areas are often hit by severe cyclonic storms with wind speeds averaging 180 km/h.
• These powerful winds can cause an abnormal rise in sea level known as a Storm Surge, where seawater is pushed across the coast, inundating settlements and agricultural fields.

Floods

A flood occurs when water overflows from rivers, streams, or other water bodies and inundates surrounding land and human settlements. Unlike many other disasters, the causes of floods are well-understood, and they often occur in predictable regions and times of the year.

Causes of Floods:

• Surface runoff exceeding the carrying capacity of river channels.
• High-intensity rainfall over a long period.
• Melting of ice and snow.
• Storm surge in coastal areas.
• Human activities like indiscriminate deforestation, unscientific agricultural practices, and blocking drainage channels.

In India, Assam, West Bengal, and Bihar are among the most flood-prone states. Rivers in Punjab and Uttar Pradesh are also vulnerable. In recent decades, states like Rajasthan, Gujarat, and Haryana have experienced flash floods, partly due to changing monsoon patterns and human obstruction of streams. Tamil Nadu often experiences floods between November and January due to the retreating monsoon.

Consequence and Control of Floods

Floods have serious consequences for both the national economy and society.

• Negative Impacts: They destroy valuable crops, damage infrastructure like roads and bridges, and render millions of people homeless. They also lead to the spread of water-borne diseases like cholera and hepatitis.
• Positive Impacts: Floods deposit fertile silt on agricultural fields, which can be beneficial for crops. Majuli (Assam), the world's largest riverine island, is known for its good paddy crops after the annual floods in the Brahmaputra river.

However, the losses far outweigh the benefits. To control floods, governments focus on measures like:

• Constructing flood protection embankments and dams.
• Promoting afforestation, especially in the upper reaches of rivers.
• Removing human encroachments from river channels and floodplains.

Droughts

A drought is an extended period with a shortage of water due to inadequate precipitation, excessive evaporation, or over-utilization of water from reservoirs and groundwater. It is a complex phenomenon involving meteorological, agricultural, and ecological factors.

Types of Droughts

• Meteorological Drought: A prolonged period of inadequate rainfall.
• Agricultural Drought: Low soil moisture, leading to crop failure. An area is not considered drought-prone if more than 30% of its cropped area is under irrigation.
• Hydrological Drought: Water levels in reservoirs, lakes, and aquifers fall below normal.
• Ecological Drought: Shortage of water causes a natural ecosystem's productivity to fail, leading to ecological distress.

Drought Prone Areas in India

Indian agriculture is heavily dependent on the monsoon, making droughts a recurring problem. About 30% of India's total area is identified as drought-prone.

• Extreme Drought Affected Areas: Most of Rajasthan west of the Aravali hills (Marusthali) and the Kachchh region of Gujarat. Districts like Jaisalmer and Barmer receive less than 90 mm of annual rainfall.
• Severe Drought Prone Area: Includes eastern Rajasthan, most of Madhya Pradesh, eastern Maharashtra, and interior parts of Andhra Pradesh, Karnataka, Tamil Nadu, and Jharkhand.
• Moderate Drought Affected Area: Northern Rajasthan, Haryana, southern Uttar Pradesh, and remaining parts of Gujarat and Maharashtra.

Consequences of Drought

Droughts have cascading effects on society and the environment.

• They lead to crop failure (scarcity of food, or akal), fodder shortages (trinkal), and water shortages (jalkal). A shortage of all three is called trikal.
• They cause large-scale death of cattle, migration of people and livestock, and the spread of waterborne diseases from consuming contaminated water.

Drought Mitigation:

• Immediate Measures: Providing safe drinking water, medicines, and fodder, and relocating people and livestock to safer areas.
• Long-term Measures: Identifying groundwater potential, planning for the inter-linking of rivers, constructing dams and reservoirs, promoting drought-resistant crops, and encouraging rainwater harvesting.

Landslides

A landslide is the rapid sliding of a large mass of bedrock and debris down a slope. While less dramatic than earthquakes or cyclones, their impact on the environment and economy can be severe. Landslides are controlled by highly localized factors, making them difficult to monitor.

Landslide Vulnerability Zones

• Very High Vulnerability Zone: Includes the young, unstable Himalayan mountains, the Andaman and Nicobar Islands, high-rainfall areas with steep slopes in the Western Ghats and Nilgiris, and northeastern regions. Areas with frequent earthquakes or intense human activity (road/dam construction) are also at very high risk.
• High Vulnerability Zone: Areas with conditions similar to the above zone. This includes all Himalayan states and northeastern states (except the plains of Assam).
• Moderate to Low Vulnerability Zone: Includes Trans-Himalayan areas like Ladakh and Spiti, the Aravallis, and rain shadow areas of the Western and Eastern Ghats. Landslides due to mining are common in states like Jharkhand, Odisha, and Chhattisgarh.
• Other Areas: States like Rajasthan, Haryana, Uttar Pradesh, Bihar, and the coastal regions of southern states are generally safe from landslides.

Consequences of Landslides

Landslides can block roads and railway lines, disrupt transportation, and affect development activities. They can also block river channels, leading to floods.

Mitigation

• Restrict construction and other development activities in high-vulnerability zones.
• Limit agriculture to valleys and areas with moderate slopes.
• Promote large-scale afforestation and construct bunds to reduce water flow.
• Encourage terrace farming in northeastern hill states to replace practices like Jhumming (slash and burn cultivation).

Disaster Management

Unlike earthquakes, disasters like cyclones are more predictable, which allows for better management. Monitoring cyclone behavior makes it possible to issue warnings and minimize damage through measures like constructing cyclone shelters and planting trees to reduce wind speed.

The Disaster Management Bill, 2005 defines a disaster as a catastrophe, mishap, or grave occurrence from natural or man-made causes that results in substantial loss of life or environmental damage, and is beyond the coping capacity of the affected community.

Conclusion

Disasters can be natural or human-made. Since it is difficult to eliminate them, the best approach is mitigation and preparedness. There are three key stages in disaster management:

1. Pre-disaster Management: This involves gathering data, creating vulnerability maps, and spreading awareness. It also includes disaster planning and taking preventive measures in vulnerable areas.
2. During Disasters: This stage focuses on emergency rescue and relief operations, such as evacuation, setting up relief camps, and supplying food, water, and medical aid.
3. Post-disaster Operations: This includes the rehabilitation and recovery of victims. It also involves building capacity to better cope with future disasters.

These measures are crucial for a country like India, where about two-thirds of its area and population are vulnerable to disasters. The introduction of the Disaster Management Bill, 2005, and the establishment of the National Institute of Disaster Management are positive steps taken by the Government of India to address this challenge.