What Is A Disaster?

What Is A Disaster?

A disaster is a sudden, calamitous event bringing great damage, loss, or destruction, often affecting a region and its people on a large scale. It is an event that overwhelms the local capacity to cope and requires assistance beyond the scope of ordinary provisions. Disasters can be natural or human-induced.

In the context of natural disasters, they are often characterized by:

• Sudden onset: Occurring quickly and without much warning.
• High impact: Causing significant loss of life, injury, property damage, and economic disruption.
• Widespread effect: Affecting a large geographical area and population.
• Overwhelming capacity: Exceeding the ability of the affected community to respond using their own resources.

Classification Of Natural Disasters

Classification Of Natural Disasters

Natural disasters can be classified based on their origin and characteristics. A common classification categorizes them as follows:

• Geological Disasters: Related to the Earth's solid crust.
  • Earthquakes
  • Volcanic Eruptions
  • Landslides
  • Tsunamis
• Hydrological Disasters: Related to water.
  • Floods (river floods, flash floods, coastal floods)
  • Droughts
  • Landslides (often triggered by heavy rainfall)
• Meteorological Disasters: Related to atmospheric phenomena.
  • Tropical Cyclones (Hurricanes, Typhoons)
  • Tornadoes
  • Thunderstorms
  • Hailstorms
  • Blizzards
  • Heatwaves
  • Cold Waves
• Climatological Disasters: Related to climate patterns.
  • Droughts
  • Wildfires (can be exacerbated by dry conditions)
  • Glacial Lake Outburst Floods (GLOFs)
• Biological Disasters: Related to living organisms.
  • Epidemics (e.g., pandemics like COVID-19)
  • Pest Infestations (e.g., locust swarms)

India, due to its diverse geography and climatic conditions, is prone to a wide range of natural disasters, particularly earthquakes, floods, droughts, and tropical cyclones.

Earthquakes

Earthquakes

An earthquake is the sudden shaking of the Earth's surface, caused by a release of energy in the Earth's crust. This energy is usually released when tectonic plates move and grind against each other, causing faults to slip.

Socio-environmental Consequences Of Earthquakes

Earthquakes can have devastating socio-environmental consequences:

• Loss of Life and Injury: Collapsing buildings, falling debris, and fires are major causes of casualties.
• Displacement of Populations: People are often forced to leave their homes due to structural damage or fear of aftershocks.
• Damage to Infrastructure: Roads, bridges, power lines, communication networks, and water supply systems are often destroyed or severely damaged.
• Economic Loss: Destruction of homes, businesses, and agricultural land leads to significant economic disruption and loss.
• Psychological Trauma: Survivors often suffer from shock, anxiety, and post-traumatic stress disorder (PTSD).
• Environmental Impact:
  • Landslides and rockfalls: Shaking can destabilize slopes.
  • Liquefaction: Saturated soil can behave like a liquid, causing structures to sink or tilt.
  • Damage to ecosystems: Changes in landforms, water bodies, and vegetation can occur.
  • Pollution: Ruptured gas lines can cause fires, and damaged sewage systems can contaminate water sources.

Effects Of Earthquakes

The immediate and secondary effects of an earthquake can be widespread:

• Ground Shaking: The most direct effect, causing buildings and structures to vibrate.
• Surface Rupture: Visible displacement of the ground along faults.
• Landslides and Rockfalls: Triggered by ground shaking, especially in hilly or mountainous regions.
• Liquefaction: Occurs in areas with soft, saturated soil, where the ground loses its strength and behaves like a fluid.
• Tsunamis: Underwater earthquakes, especially those involving vertical displacement of the seafloor, can generate large ocean waves.
• Fires: Ruptured gas lines and electrical wires can ignite fires, which can spread rapidly, especially if water supply is disrupted.
• Flooding: Dam breaches or disruption of water management systems can cause floods.

Earthquake Hazard Mitigation

Mitigation aims to reduce the impact of earthquakes:

• Building Codes and Seismic Design: Constructing buildings and infrastructure to withstand seismic forces is crucial. This involves using flexible materials, reinforcing structures, and adhering to strict building codes.
• Land-Use Planning: Avoiding construction on active fault lines or areas prone to liquefaction.
• Public Awareness and Education: Educating the public about earthquake safety, including how to prepare for, during, and after an earthquake (e.g., "Drop, Cover, Hold On").
• Early Warning Systems: Developing and implementing systems that can detect earthquakes and provide advance warnings to allow for some protective actions.
• Retrofitting Older Structures: Strengthening existing buildings that do not meet current seismic standards.
• Preparedness Plans: Establishing emergency response plans at national, regional, and local levels.

Tsunami

Tsunami

A tsunami is a series of large ocean waves, typically caused by underwater earthquakes, volcanic eruptions, or landslides. These waves can travel across vast oceans at high speeds and can cause immense destruction when they reach coastal areas.

The word "tsunami" comes from Japanese, meaning "harbor wave," reflecting how these waves often appear most destructive in harbors and bays.

Causes:

• Underwater Earthquakes: The most common cause, particularly those with a vertical displacement of the seafloor.
• Volcanic Eruptions: Explosive eruptions or the collapse of volcanic cones into the sea.
• Underwater Landslides: Large masses of sediment sliding down the continental slope.
• Meteorite Impacts: Though rare, a large meteorite hitting the ocean could generate a tsunami.

Effects:

• Inundation: Massive flooding of coastal areas, pushing far inland.
• Destruction of Infrastructure: Buildings, roads, bridges, and ports are destroyed by the force of the waves and debris carried by them.
• Loss of Life: Due to drowning, impact from debris, and being swept out to sea.
• Environmental Damage: Salinization of soil and freshwater sources, destruction of coastal ecosystems like coral reefs and mangroves.
• Economic Devastation: Damage to fishing fleets, aquaculture, tourism infrastructure, and other coastal industries.

Mitigation:

• Tsunami Warning Systems: Networks of seismometers and ocean buoys to detect earthquakes and measure wave activity, coupled with communication systems to alert coastal populations.
• Coastal Zone Management: Developing land-use plans that restrict construction in high-risk inundation zones.
• Coastal Vegetation: Planting mangrove forests and other vegetation along coastlines can act as natural barriers against tsunami waves.
• Public Education: Raising awareness about tsunami risks and evacuation procedures.

Tropical Cyclone

Tropical Cyclone

A tropical cyclone is a rotating storm system characterized by a low-pressure center, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain. These storms form over warm tropical or subtropical waters.

Structure Of Tropical Cyclone

A tropical cyclone has a distinct structure:

• Eye: The calm, clear, and low-pressure center of the storm. Winds are light here, and it is often sunny.
• Eyewall: The ring of intense thunderstorms surrounding the eye. This is where the strongest winds and heaviest rainfall occur.
• Rainbands: Spiraling bands of thunderstorms and rain that extend outward from the eyewall.
• Outflow: The upper-level expulsion of air, which helps maintain the low pressure at the surface.

The formation and intensification of tropical cyclones depend on warm ocean waters (at least $26.5^\circ$C), low vertical wind shear, and moisture.

Spatio-temporal Distribution Of Tropical Cyclone In India

India is particularly vulnerable to tropical cyclones, mainly affecting its eastern and western coastlines:

• Frequency: Tropical cyclones are most frequent during the post-monsoon season (October-December) and the pre-monsoon season (May-June). The Bay of Bengal and the Arabian Sea are the primary breeding grounds for these storms.
• Bay of Bengal: This basin is more active, contributing to the majority of cyclones that strike India. The eastern coast, including states like Odisha, Andhra Pradesh, Tamil Nadu, and West Bengal, is frequently hit.
• Arabian Sea: Cyclones are less frequent but can still be intense. The western coast, particularly Gujarat, Maharashtra, and Kerala, can be affected.
• Intensity: Cyclones vary in intensity, categorized by wind speed (e.g., depression, deep depression, cyclonic storm, severe cyclonic storm).

Consequences Of Tropical Cyclones

The impact of tropical cyclones can be catastrophic:

• High-speed Winds: Winds can reach speeds of over 200 km/h, causing widespread destruction to buildings, trees, and infrastructure.
• Heavy Rainfall: Intense rainfall can lead to severe flooding and landslides, especially in hilly areas.
• Storm Surge: This is one of the most dangerous aspects. A storm surge is an abnormal rise of sea level during a cyclone, caused by low pressure and strong onshore winds. It can inundate low-lying coastal areas, causing massive destruction and loss of life.
• Inundation and Erosion: Coastal flooding and erosion can significantly alter the landscape.
• Economic Losses: Damage to agriculture, fisheries, housing, and infrastructure leads to severe economic setbacks.
• Loss of Life and Injury: Direct impact from high winds, flying debris, drowning from storm surges, and floods.

Mitigation measures include early warning systems, evacuation plans, building cyclone-resistant structures, and coastal afforestation (especially mangroves).

Floods

Floods

Floods are the most common natural disaster in India. They occur when an overflow of water submerges land that is usually dry. This can happen due to heavy rainfall, rapid snowmelt, storm surges, or dam failures.

Consequence And Control Of Floods

Consequences of Floods:

• Loss of Life and Injury: Drowning is the primary cause of death.
• Damage to Property: Homes, buildings, and infrastructure are damaged or destroyed by the force of water and debris.
• Agricultural Losses: Crops are destroyed, and agricultural land can be rendered infertile due to waterlogging and soil erosion.
• Disruption of Services: Power, communication, transportation, and water supply systems are often disrupted.
• Health Hazards: Floods can lead to outbreaks of water-borne diseases like cholera and typhoid due to contamination of water sources.
• Economic Impact: Significant loss to agriculture, industry, and infrastructure.
• Displacement: Large numbers of people are often displaced from their homes.

Flood Control Measures:

• Construction of Dams and Reservoirs: To store excess water and regulate river flow.
• Building Embankments and Levees: To contain rivers within their channels.
• Channel Improvement: Dredging and widening river channels to increase their capacity.
• Flood Forecasting and Warning Systems: Timely alerts to enable evacuation and preparedness.
• Afforestation and Watershed Management: To reduce soil erosion and increase infiltration, thereby reducing runoff.
• Land-Use Planning: Discouraging construction in flood-prone areas.
• Drainage Improvement: Enhancing drainage systems in urban and rural areas.

Droughts

Droughts

A drought is a prolonged period of abnormally low rainfall, leading to a shortage of water. It is a slow-onset disaster that can have widespread and severe impacts on agriculture, water resources, and the economy.

Types Of Droughts

Droughts can be classified based on their characteristics:

• Meteorological Drought: Defined by the degree of dryness (lack of precipitation) compared to the regional average.
• Agricultural Drought: Occurs when there is insufficient soil moisture to meet the needs of crops and pastures.
• Hydrological Drought: Occurs when the water levels in rivers, reservoirs, and groundwater aquifers fall below average.
• Socio-economic Drought: Occurs when the demand for water exceeds the available supply, affecting human activities and economic systems.

Drought Prone Areas In India

Several regions in India are particularly susceptible to droughts:

• Rain Shadow Regions: Areas like the leeward side of the Western Ghats, parts of Rajasthan, Gujarat, and Madhya Pradesh receive very little rainfall.
• Interior Peninsular India: Large parts of Maharashtra, Karnataka, Telangana, and Andhra Pradesh are frequently affected by drought.
• Parts of Uttar Pradesh and Bihar: Especially in the Bundelkhand region and eastern parts of these states.
• Parts of Tamil Nadu and Odisha.

These areas often experience a deficit in monsoon rainfall or uneven distribution of rain.

Consequences Of Drought

The consequences of drought are far-reaching:

• Agricultural Failure: Crop yields decline drastically, leading to food shortages and economic losses for farmers.
• Water Scarcity: Shortages of drinking water for humans and livestock.
• Famine and Malnutrition: Food insecurity can lead to widespread hunger and malnutrition.
• Economic Losses: Impact on agriculture, livestock, and related industries.
• Migration: People may be forced to migrate from drought-affected areas in search of water and livelihood.
• Environmental Degradation: Increased risk of soil erosion, desertification, and loss of biodiversity.
• Social Unrest: Competition for scarce water resources can sometimes lead to social tensions.

Mitigation measures include promoting water conservation, rainwater harvesting, adopting drought-resistant crops, improving irrigation efficiency, and developing early warning systems.

Landslides

Landslides

Landslides are the movement of a mass of rock, debris, or earth down a slope. They are often triggered by heavy rainfall, earthquakes, volcanic eruptions, or human activities like deforestation and construction on steep slopes.

Landslide Vulnerability Zones

In India, landslide vulnerability is highest in the:

• Himalayan Region: Especially the northern states like Uttarakhand, Himachal Pradesh, Jammu and Kashmir, and the Northeast states. This is due to the young and unstable geology of the Himalayas, steep slopes, and heavy monsoon rainfall.
• Western Ghats: Areas with steep slopes and heavy rainfall are also prone to landslides.
• Eastern Ghats and other hilly regions.

Areas with loose soil, steep slopes, seismic activity, and deforestation are more vulnerable.

Consequences Of Landslides

Landslides can cause significant damage:

• Loss of Life and Injury: People caught in the path of a landslide can be buried or injured.
• Damage to Infrastructure: Roads, bridges, buildings, and power lines can be destroyed or blocked.
• Disruption of Transportation: Roads become impassable, cutting off communities and hindering relief efforts.
• Environmental Impact: Forests can be destroyed, and rivers can be blocked by debris, leading to potential flooding upstream or altered river courses.
• Economic Losses: Damage to property, loss of agricultural land, and disruption of economic activities.

Mitigation

Mitigation strategies for landslides include:

• Structural Measures:
  • Retaining Walls: To support slopes.
  • Terracing: To reduce the steepness of slopes.
  • Drainage Control: Improving drainage to prevent water accumulation, which can destabilize slopes.
  • Rock Bolts and Nets: To stabilize loose rock masses.
• Non-Structural Measures:
  • Land-Use Zoning: Restricting development in high-risk landslide areas.
  • Afforestation: Planting trees with strong root systems to bind the soil.
  • Public Awareness and Education: Informing communities about landslide risks and safety measures.
  • Early Warning Systems: Monitoring slope stability and weather conditions to predict potential landslides.

Disaster Management

Disaster Management

Disaster Management is a continuous and integrated multi-sectoral approach to build disaster resilient communities. It involves a cycle of activities encompassing prevention, mitigation, preparedness, response, and recovery.

Key components of Disaster Management: