Chapter 6 — Natural Hazards and Disasters

Natural hazards are elements or circumstances in the natural environment that have the potential to cause harm to people or property. Natural disasters are relatively sudden events that actually cause large-scale, widespread death, loss of property, and disturbance to social systems — events where the magnitude of destruction is very high. All hazards do not turn into disasters.

Based on analysis of over 1,200 historical earthquakes, India is divided into five zones: Very High Damage Risk, High Damage Risk, Moderate, Low, and Very Low. The Very High zone includes the northeast states, areas north of Darbhanga and Araria (Bihar), Uttarakhand, Western Himachal Pradesh (around Dharamshala), Kashmir Valley, and Kuchchh (Gujarat). The High zone includes remaining parts of J&K, Ladakh, Himachal Pradesh, Northern Punjab, Eastern Haryana, Delhi, Western Uttar Pradesh, and Northern Bihar. The most stable areas are in the Deccan plateau.

The Indian plate moves at a speed of one centimetre per year towards the north and northeast and is constantly obstructed by the Eurasian plate. This causes both plates to lock, leading to accumulation of energy at different points. Excessive energy buildup causes stress that ultimately breaks the lock, releasing energy suddenly as earthquakes along the Himalayan arch.

In deep ocean, a tsunami has a very long wave-length and limited wave-height — it raises a ship only 1–2 metres over several minutes and is difficult to detect. When it enters shallow water, the wave-length decreases while the period remains unchanged, which greatly increases wave height — sometimes to 15 m or more. This causes large-scale destruction along shores, which is why tsunamis are also called Shallow Water Waves.

Four conditions are required: (i) a large, continuous supply of warm and moist air that can release enormous latent heat; (ii) a strong Coriolis force to prevent filling of the low-pressure centre (which is why cyclones cannot form between 0°–5° latitude); (iii) unstable conditions through the troposphere to create local disturbances; and (iv) absence of a strong vertical wind wedge that would disturb vertical transport of latent heat.

The four types are: (i) Meteorological Drought — prolonged inadequate rainfall with poor distribution over time and space; (ii) Agricultural (Soil Moisture) Drought — low soil moisture that leads to crop failures; areas with more than 30% of gross cropped area under irrigation are excluded from this category; (iii) Hydrological Drought — water levels in aquifers, lakes, and reservoirs fall below what precipitation can replenish; (iv) Ecological Drought — productivity of a natural ecosystem fails due to water shortage causing ecological distress.

According to the chapter, nearly 19 per cent of India's total geographical area and 12 per cent of its total population suffer due to drought every year. About 30 per cent of the country's total area is identified as drought-prone, affecting around 50 million people.

Assam, West Bengal, and Bihar are among the high flood-prone states. Northern states like Punjab and Uttar Pradesh face occasional floods. Rajasthan, Gujarat, Haryana, and Punjab have seen flash floods in recent decades — partly due to monsoon patterns and partly due to blocking of streams by human activities. Tamil Nadu experiences flooding during November–January due to the retreating monsoon. Human activities like deforestation, unscientific agricultural practices, and colonisation of flood plains intensify floods.

India is divided into four zones: Very High Vulnerability — unstable young Himalayan areas, Andaman and Nicobar, Western Ghats, Nilgiris, northeast, and areas with frequent earthquakes or intense construction activity; High Vulnerability — all Himalayan states and northeast regions except the plains of Assam; Moderate to Low Vulnerability — Trans-Himalayan Ladakh and Spiti, Aravali, rain shadow areas of Western and Eastern Ghats, Deccan plateau; Other (Safe) Areas — Rajasthan, Haryana, Uttar Pradesh, Bihar, most of West Bengal and Assam (except specific districts), and southern coastal regions.

The three stages are: (i) Pre-disaster management — generating data and information, preparing vulnerability zoning maps, spreading awareness, disaster planning and preventive measures; (ii) During disasters — rescue and relief operations such as evacuation, construction of shelters and relief camps, supplying water, food, clothing, and medical aid on an emergency basis; (iii) Post-disaster operations — rehabilitation and recovery of victims, and capacity-building to cope with future disasters.

The Yokohama Strategy and Plan of Action for a Safer World was adopted at the World Conference on Natural Disaster Reduction held in Yokohama, Japan, from May 23–27, 1994. It acknowledged that natural disaster impacts had risen and that developing countries, especially the least developed, were worst affected. It called on nations to develop national disaster prevention and mitigation capacities, promote regional and international cooperation, and share technology and information. It also declared 1990–2000 as the International Decade for Natural Disaster Reduction (IDNDR).

The December 26, 2004 tsunami caused more than 300,000 people to lose their lives. The chapter states that mitigation of tsunami hazards is beyond the capacity of any individual state or government because losses occur on a much larger scale. Combined efforts at the international level are the only viable approach. After this disaster, India volunteered to join the International Tsunami Warning System.

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