Natural Hazards and Disasters: Tropical Cyclone, Floods, Drought and Landslides

Understanding natural hazards and disasters like tropical cyclones, floods, droughts, and landslides is crucial for preparedness and mitigation efforts. Disasters result from a combination of hazards, vulnerability, and insufficient capacity to cope, impacting communities and societies. Exploring the causes, distribution patterns, and vulnerabilities associated with these events helps in developing strategies to minimize their impact.

Natural Hazards and Disasters: Disaster, Hazard, Vulnerability, and Risk

• Disaster: It can be defined as “A serious disruption in the functioning of the community or a society causing widespread material, economic, social or environmental losses which exceed the ability of the affected society to cope using its own resources”. 
  • It is a result of the combination of hazard, vulnerability and insufficient capacity to reduce the potential chances of risk.
• Hazard: It may be defined as “a dangerous condition or event that threatens or has the potential for causing injury to life or damage to property or the environment’’.
• Vulnerability: It may be defined as “the extent to which a community, structure, services or geographic area is likely to be damaged or disrupted by the impact of a particular hazard, on account of their nature, construction and proximity to hazardous terrains or disaster-prone area”. Vulnerabilities can be categorized into:
• Physical Vulnerability: It includes notions of who and what may be damaged or destroyed by natural hazards. 
  • It is based on the physical condition of people and elements at risk, such as buildings, infrastructure etc.
• Socio-economic Vulnerability: refers to the degree to which individuals and communities are susceptible to harm from disasters due to their social and economic status.
• Risk: is a measure of the expected losses due to a hazard event occurring in a given area over a specific time period. 

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Natural Hazards: Understanding and Managing

A. Tropical Cyclone

• Tropical cyclones are intense low-pressure areas confined to the area lying between 30°N and 30° S latitudes around which high-velocity winds blow. . 
• It is energised by the release of latent heat condensation of moisture that the wind gathers after moving over the oceans and seas.
• Condition for tropical cyclone
  • Warm Sea Surface Temperature: above 27 degrees Celsius.
  • Supply Warm and Moist Air: Large and continuous supply of warm and moist air  drives it due to the release of latent heat.
  • Strong Coriolis Force: that can prevent the filling of low pressure at the centre (absence of Coriolis force near the equator prohibits the formation of tropical cyclones between 0°-5°latitude).
  • Unstable Conditions: in the troposphere that create local disturbances around which a cyclone develops.
  • Absence of Strong Vertical Wind Wedge: which disturbs the vertical transport of latent heat.
  • Spatio-temporal Distribution of Tropical Cyclones in India
  • Owing to its Peninsular shape, the tropical cyclones in India originate in – Bay of Bengal (majority of cyclones) and Arabian Sea.
  • Most of the cyclones originate between 10°-15°north latitudes during the monsoon season. However, in the case of the Bay of Bengal, cyclones mostly develop during the months of October and November.

B. Floods

• Distributional Pattern of Floods in India
• Rashtriya Barh Ayog (National Flood Commission) identified 40 million hectares of land as flood-prone in India. 
  • Most flood-affected states are Assam, West Bengal and Bihar.
• Most of the rivers in the northern states like Punjab and Uttar Pradesh are also vulnerable to occasional floods. 
• Sometimes, Tamil Nadu experiences flooding during November-January due to the retreating monsoon. 

C. Droughts

• Types of Droughts
  • Meteorological Drought: caused by prolonged periods of inadequate rainfall marked with mal-distribution of the same over time and space.
  • Hydrological Drought: Availability of water in different storages and reservoirs like aquifers, lakes, reservoirs, etc. falls below what the precipitation can replenish.
  • Agricultural Drought: is also known as soil moisture drought, characterised by low soil moisture that is necessary to support the crops. 
    • Moreover, if an area has more than 30 percent of its gross cropped area under irrigation, the area is excluded from the drought-prone category.
  • Ecological Drought: When the productivity of a natural ecosystem fails due to a shortage of water and as a consequence of ecological distress, damages are induced in the ecosystem.
• Drought Areas in India
• • On the basis of the severity of droughts, India can be divided into the following regions:
  • Extreme Drought Affected Areas: Most parts of Rajasthan, particularly areas to the west of the Aravali hills, 
    • Examples: Marusthali and Kachchh regions of Gujarat. 
  • Severe Drought Prone Area: Parts of eastern Rajasthan, most parts of Madhya Pradesh, eastern parts of Maharashtra, interior parts of Andhra Pradesh and Karnataka Plateau, northern parts of interior Tamil Nadu and southern parts of Jharkhand and interior Odisha are included in this category.
  • Moderate Drought Affected Area: Northern parts of Rajasthan, Haryana, southern districts of Uttar Pradesh, the remaining parts of Gujarat, Maharashtra except Konkan, Jharkhand and Coimbatore plateau of Tamil Nadu and interior Karnataka. 

D. Landslides

• Definition: A sudden movement of rock, boulders, earth or debris down a slope is termed a landslide. 
  • Landslides occur mainly in mountainous terrains where there are conducive conditions of soil, rock, geology and slope
• Landslide Vulnerability Zones
• Very High Vulnerability Zone: 
  • Highly unstable, relatively young mountainous areas in the Himalayas and Andaman and Nicobar.
  • High rainfall regions with steep slopes in Western Ghats and Nilgiris, north-eastern regions.
  • Areas that experience frequent ground-shaking due to earthquakes. 
  • Areas of intense human activities like construction of roads, dams, etc.
• High Vulnerability Zone: All the Himalayan states and the states from the northeastern regions except the plains of Assam are included in the high vulnerability zones.
• Moderate to Low Vulnerability Zone: 
  • Areas that receive less precipitation such as Trans-Himalayan areas of Ladakh and Spiti (Himachal Pradesh).
  • Undulated yet stable relief and low precipitation areas in the Aravali.
  • Rain shadow areas in the Western and Eastern Ghats.
  • The Deccan plateau also experiences occasional landslides. 
  • Landslides due to mining and subsidence are most common in states like Jharkhand, Odisha, Chhattisgarh, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Tamil Nadu, Goa and Kerala.
• Other Areas: The remaining parts of India, particularly states like Rajasthan, Haryana, Uttar Pradesh, Bihar, West Bengal (except district Darjeeling), Assam (except district Karbi Anglong) and Coastal regions of the southern States are safe as far as landslides are concerned.

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Conclusion

Understanding natural hazards, such as tropical cyclones, floods, droughts, and landslides is vital for effective disaster management. By understanding the causes, distributional patterns, and vulnerabilities, communities can better prepare and respond to these events, mitigating their adverse effects and enhancing resilience. Collaboration, awareness, and proactive measures are key to building safer and more resilient societies in the face of these challenges.

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