Chapter 6 — Hazards and Disasters

A hazard is any natural or human event or condition that has the potential to cause harm to people, property, the economy or the environment. The key word is potential. A cyclone spinning over the empty Bay of Bengal is a hazard; a fault line under a mountain is a hazard; a leaking gas cylinder in a kitchen is a hazard. Nothing has yet been lost, but something could be.

A disaster is what happens when a hazard actually strikes a vulnerable community and produces losses so large that the community cannot cope with them on its own. When the same cyclone crosses the crowded coast of the Sundarbans and drowns villages, or the fault slips and flattens a town, the hazard has become a disaster. The United Nations describes a disaster as a serious disruption of the functioning of a society, causing widespread human, material or environmental losses that exceed the ability of the affected society to cope using its own resources.

So the difference can be summed up in one line: hazard is the cause, disaster is the effect. Every disaster begins as a hazard, but not every hazard becomes a disaster. Whether it does depends on three things:

• Magnitude of the hazard — a magnitude 4 earthquake does little, a magnitude 8 earthquake can destroy a region.
• Exposure — how many people, houses and fields lie in the path of the event. An earthquake in an empty desert is not a disaster.
• Vulnerability — how weak the community is. Poor houses, no warning system, no trained volunteers and no savings all turn a moderate hazard into a great disaster.

Geographers therefore write the relationship as Disaster risk = Hazard × Vulnerability, sometimes divided by the capacity of the community to cope. This equation is important because it tells us that a disaster is not only an act of nature. Nature supplies the hazard, but human choices decide the vulnerability. Building on a flood plain, cutting forests on a hill slope and ignoring a cyclone warning are all human decisions that increase risk.

Two more terms are used in this chapter. Catastrophe is a disaster of very great scale, such as the 2004 tsunami that killed more than two lakh people in fourteen countries. Calamity is the older word used in Indian government documents for a disaster; the Calamity Relief Fund was the earlier name of today's disaster response funds.

Hazards are grouped according to their origin, that is, according to what produces them. The chapter uses a three-fold classification.

1. Natural hazards arise from processes of the earth itself and are not caused by people. They are further divided by the part of the earth system that produces them:

• Geological or tectonic hazards come from the crust — earthquakes, volcanic eruptions, landslides, avalanches and tsunamis.
• Atmospheric or meteorological hazards come from the air — tropical cyclones, tornadoes, hailstorms, heat waves, cold waves, lightning and drought.
• Hydrological hazards come from water — river floods, flash floods, storm surges and glacial lake outburst floods.
• Biological hazards come from living things — epidemics such as cholera and malaria, locust swarms and crop pests.

2. Quasi-natural hazards are events that look natural but are largely triggered or made worse by human activity. Soil erosion after deforestation, landslides caused by road cutting, floods made worse by encroachment of river beds, desertification through overgrazing and smog produced by pollution all belong here. The name means half-natural.

3. Man-made or anthropogenic hazards are entirely the result of human action or negligence. They include fires in markets and slums, industrial accidents such as the Bhopal gas leak of 1984, nuclear accidents such as Chernobyl in 1986, dam failures, building collapses, road, rail and air accidents, stampedes at crowded gatherings, riots and war.

Hazards may also be classified by speed of onset. Rapid-onset hazards such as earthquakes, flash floods and explosions strike within minutes and leave no time to run; preparation must be done in advance. Slow-onset hazards such as drought, famine, sea-level rise and desertification build up over weeks or years; here early warning and planned response can prevent most of the damage.

A third way of grouping uses area affected: local hazards such as a house fire or a single landslide; regional hazards such as a cyclone that crosses three districts; and global hazards such as climate change or a pandemic. Finally, hazards are described by frequency — floods in the Ganga delta are annual, a great earthquake on a fault may recur only once in centuries — and by duration, from the thirty seconds of an earthquake to the months of a drought.

Understanding the class of a hazard helps in choosing the right response. Geological hazards cannot be prevented, so the answer is strong construction and land-use planning. Atmospheric hazards can be forecast, so the answer is warning and evacuation. Man-made hazards can, in principle, be prevented entirely through safety rules and their strict enforcement.

An earthquake is a sudden shaking of the ground caused by the release of energy stored in the rocks of the earth's crust. The energy travels outward as seismic waves, and the shaking they produce at the surface is what we feel.

Causes. The main cause is plate tectonics. The crust and upper mantle form rigid plates that move slowly over the softer asthenosphere. Where plates collide, slide past each other or pull apart, enormous stress builds up along faults. Rocks bend like a spring until they break; the stored strain is released in seconds and the ground snaps into a new position. This is called the elastic rebound theory. Almost all great earthquakes occur along plate boundaries — the Circum-Pacific belt (the Ring of Fire) has about 68 per cent of the world's earthquakes and the Alpine-Himalayan belt about 21 per cent. India sits on the Indian plate, which is pushing north into the Eurasian plate at about 5 cm a year, and this is why the Himalaya and the north-east are so earthquake-prone.

Other causes are volcanic activity, in which rising magma cracks the surrounding rock; the collapse of underground caves or mines; landslides; and human actions such as the filling of big reservoirs (reservoir-induced seismicity, as at Koyna in Maharashtra in 1967), deep mining and underground nuclear tests.

Focus and epicentre. The point inside the earth where the rupture begins is the focus or hypocentre. The point on the surface directly above it is the epicentre, where the shaking is usually strongest. Earthquakes with a shallow focus (0–70 km) are the most destructive.

Seismic waves. Three kinds are recorded. P waves (primary) are compressional, travel fastest, and pass through solids and liquids. S waves (secondary) are transverse, slower, and cannot pass through liquids, which is how we know the outer core is liquid. Surface waves (L waves) travel along the crust, arrive last, and cause the most damage.

Measurement. The instrument is the seismograph; its record is a seismogram. Two scales are used. The Richter scale (1935) measures magnitude, the energy released, on a logarithmic scale from 1 upward: each whole step means about 10 times the ground motion and about 32 times the energy. A magnitude below 4 is minor, 5–6 moderate, 7 major and 8 or more great. The Mercalli scale measures intensity, the observed effects, in twelve grades from I (not felt) to XII (total destruction). Magnitude is one number for the whole earthquake; intensity varies from place to place.

The effects of an earthquake can be divided into primary effects, which come from the shaking itself, and secondary effects, which follow from it.

Primary effects. Ground shaking cracks and collapses buildings, bridges, dams and roads. Ground rupture opens fissures along the fault. In loose, water-soaked soil the ground may behave like a liquid — liquefaction — and whole buildings tilt or sink. Landslides and rockfalls are triggered on slopes. In the 2001 Bhuj earthquake the town of Bhuj and the new city of Anjar were almost destroyed, and in the 2015 Nepal earthquake nearly six lakh houses were flattened.

Secondary effects. Fires break out from broken gas pipes and electric lines and are often more deadly than the shaking, as in Tokyo in 1923. Bursting dams cause floods. Undersea earthquakes cause tsunamis. Broken water pipes and sewers lead to epidemics. Roads and railways are cut, so relief cannot reach. Industry and trade stop, people lose jobs and homes, and children lose schooling for months.

Why earthquakes cannot be predicted. Scientists can say where earthquakes are likely and how big they might be, but not when. Warning signs such as changes in groundwater level, radon gas, animal behaviour and small foreshocks are studied but are not reliable. Therefore earthquake management depends on preparation, not on warning.

Pre-disaster measures.

• Seismic zoning. India is divided into four zones. Zone V (very high risk) covers the whole north-east, Kashmir, parts of Himachal, Uttarakhand, Kutch and the Andaman and Nicobar Islands. Zone IV includes Delhi, north Bihar and North Bengal including Darjeeling and Jalpaiguri. Kolkata falls in Zone III, moderate risk.
• Earthquake-resistant construction. Light roofs, reinforced concrete columns tied to beams, steel bands at plinth and lintel level, and flexible joints. Traditional designs such as the wooden-framed houses of Kashmir and the bamboo houses of Assam survive quakes well.
• Building codes of the Bureau of Indian Standards must be enforced, especially for schools and hospitals.
• Drills in schools: Drop, Cover and Hold.

During the earthquake. Stay indoors under a strong table or desk, away from windows, cupboards and hanging objects; if outdoors, move to open ground away from buildings, trees and electric wires; if in a vehicle, stop in an open place and stay inside.

Post-disaster measures. Search and rescue within the first 72 hours, when survival chances are highest; first aid and evacuation of the injured; supply of water, food, shelter and medicine; restoration of electricity, roads and communication; and then rehabilitation — rebuilding houses to a safer design, restoring livelihoods and counselling the traumatised.

A volcano is an opening in the earth's crust through which molten rock (magma below ground, lava at the surface), gases, ash and rock fragments are thrown out. The eruption is driven by gases dissolved in the magma; as the magma rises, pressure falls, the gases expand and the mixture is forced out, sometimes gently and sometimes with explosive violence.

Where volcanoes occur. Like earthquakes, volcanoes follow plate boundaries. Where one plate dives under another (subduction), as around the Pacific, the melting plate feeds explosive volcanoes such as Mount Fuji, Krakatoa and Pinatubo. Where plates pull apart, as along the Mid-Atlantic Ridge, quieter basaltic volcanoes form, as in Iceland. A few, such as the Hawaiian volcanoes, sit over hot spots in the mantle far from any boundary. India's only active volcano is on Barren Island in the Andaman Sea, which erupted in 1991, 2005 and 2017; Narcondam nearby is dormant.

Types by activity. Active volcanoes erupt regularly (Etna, Stromboli, Barren Island). Dormant volcanoes are sleeping but may wake (Fuji, Vesuvius). Extinct volcanoes have not erupted in recorded history and are not expected to (Kilimanjaro, Popa in Myanmar).

Hazards produced by an eruption.

• Lava flows bury fields and villages; they move slowly, so they destroy property rather than lives.
• Pyroclastic flows — avalanches of hot gas and ash at 500–700 °C travelling at over 100 km per hour — are the greatest killer. Pompeii in 79 CE and Mount Pelée in 1902 (28,000 dead) were destroyed by them.
• Ash fall collapses roofs, chokes lungs, ruins crops and stops aircraft, as the 2010 Icelandic eruption stopped European air traffic for a week.
• Lahars are mud flows of ash mixed with rain or melted snow that race down valleys.
• Poisonous gases such as sulphur dioxide and carbon dioxide can suffocate; a burst of CO₂ from Lake Nyos in Cameroon killed 1,700 people in 1986.
• Tsunamis follow undersea or island eruptions; Krakatoa in 1883 produced waves 30 m high that killed 36,000 people.
• Climate effects: dust and sulphur in the stratosphere cool the earth; the year after Tambora (1815) was the year without a summer.

Benefits. Volcanic hazards must be balanced against benefits: volcanic soils are among the most fertile in the world (Java, the Deccan), volcanoes give geothermal energy, sulphur, building stone and gemstones, and volcanic islands and hot springs attract tourists. That is why people continue to live near them.

Management. Volcanoes can usually be predicted better than earthquakes. Rising ground temperature, swelling of the cone, small tremors and increased gas emission all give warning of days or weeks. Monitoring stations, hazard maps showing likely lava and lahar paths, exclusion zones, evacuation plans and strong sloping roofs are the main measures. The evacuation of 60,000 people before the 1991 Pinatubo eruption saved thousands of lives.

A landslide is the rapid downward movement of a mass of rock, soil or debris along a slope under the pull of gravity. It is a form of mass movement, and it is the most frequent natural hazard in the hilly districts of West Bengal.

Conditions and causes. A slope fails when the force pulling material downward exceeds the friction and cohesion holding it in place. Several factors tip the balance:

• Steep slopes — the steeper the slope, the greater the downslope component of gravity.
• Weak or weathered rock — the Darjeeling hills are made of soft, fractured, deeply weathered gneiss, schist and phyllite that break easily.
• Heavy rain — water adds weight, fills the pores, raises pore pressure and acts as a lubricant along bedding planes. Almost every landslide in the Darjeeling Himalaya follows a spell of heavy monsoon rain; the disaster of October 1968 followed 1,000 mm of rain in three days.
• Earthquakes shake loose material free; the 2011 Sikkim earthquake triggered hundreds of slides.
• Removal of vegetation — tree roots bind soil; deforestation for tea gardens, firewood and building leaves slopes bare.
• Human cutting of slopes for roads (the Hill Cart Road), railways and houses removes the toe of the slope that supported everything above it.
• Unplanned building and poor drainage — leaking pipes and blocked drains soak the slope from inside.

Types. Rockfall is the free fall of blocks from a cliff. Slide is the movement of a coherent mass along a plane. Slump is a rotational slide along a curved surface. Debris flow or mudflow is a wet, fluid mass that races down a valley. Creep is the very slow, almost invisible downhill movement of soil, shown by tilted poles and bent tree trunks.

Effects. Villages, roads and railway lines are buried; the Darjeeling Himalayan Railway and the National Highway are cut every monsoon. Rivers are dammed, and the temporary lakes burst to cause floods downstream. Farmland and tea gardens are lost. Communication is broken so relief cannot reach. The July 2015 Darjeeling landslides, centred on Mirik, killed about 40 people.

Management. Prevention is largely possible for landslides, unlike earthquakes.

• Landslide hazard zonation maps identify unstable slopes; building should be banned there.
• Afforestation with deep-rooted trees and grasses binds the soil.
• Drainage — surface drains, French drains and horizontal drainage pipes keep water out of the slope.
• Engineering works — retaining walls, gabion walls (wire cages of stone), rock bolts, wire netting over cliffs, terracing and reducing slope angle.
• Regulating construction and road cutting, and moving people from the most dangerous sites.
• Warning based on rainfall thresholds, and rain gauges linked to alerts.

A flood occurs when water overflows the banks of a river or covers land that is normally dry. A flood is the most common and the most widespread natural disaster in India; about one-eighth of the country's area is flood-prone, and West Bengal, with its low deltaic plains crossed by the Ganga, the Damodar, the Ajay, the Mayurakshi, the Teesta and the Jalangi, is one of the worst affected states.

Natural causes.

• Heavy and concentrated monsoon rainfall — West Bengal receives about 80 per cent of its rain between June and September, and a single depression from the Bay of Bengal can drop 300 mm in a day.
• Low gradient and flat relief — the delta slopes only a few centimetres per kilometre, so water drains very slowly.
• Silting of river beds — rivers such as the Bhagirathi and the Damodar have raised beds, so even moderate floods spill over.
• Tidal backwater — high tides in the Hooghly hold up river water and push it back over the banks; in the Sundarbans a storm surge does the same.
• Sudden release from upstream — snowmelt and rain in the Himalaya swell the Teesta, Torsa and Jaldhaka, which flood the Duars within hours.

Human causes. Deforestation in the catchment increases run-off and silt. Encroachment on flood plains, filling of wetlands and ponds, and roads and railway embankments without enough culverts block natural drainage. Poor maintenance of embankments leads to breaches. Release of water from dams such as Maithon and Panchet on the Damodar during heavy rain, to save the dams, floods Bardhaman, Hooghly and Howrah below.

Effects. Loss of life by drowning; loss of crops, especially the standing aman paddy; loss of cattle; destruction of mud houses; contamination of drinking water and outbreaks of diarrhoea and cholera; snake bite; displacement of lakhs of people; and damage to roads, bridges and railways. But floods also have a positive side: they spread fertile silt, recharge groundwater and fill ponds and wetlands with fish.

Management.

• Structural measures: embankments and levees along rivers (though they raise the bed in the long run), dams and reservoirs such as the Damodar Valley Corporation dams built after the disastrous 1943 Damodar flood, diversion channels, dredging of river beds and improved drainage.
• Non-structural measures: flood forecasting by the Central Water Commission and the India Meteorological Department, flood-plain zoning to keep houses off the lowest land, afforestation in catchments, raised platforms and flood shelters in villages, community boats, and crop insurance.
• During a flood: move to higher ground with dry food, drinking water, medicines and documents; never walk or drive through fast-moving water; listen to radio warnings.
• After a flood: boil or chlorinate water, use oral rehydration solution, remove carcasses and debris, and restore embankments before the next season.

A tropical cyclone is a violent rotating storm that forms over warm tropical oceans, with very low pressure at its centre, winds spiralling inward at more than 62 km per hour and torrential rain. In the Bay of Bengal it is simply called a cyclone; the same storm is a hurricane in the Atlantic and a typhoon in the western Pacific. West Bengal's coast, especially the Sundarbans, is one of the most cyclone-prone stretches in the world.

Conditions of formation. A sea surface temperature of at least 27 °C over a large area; a location at least 5° of latitude away from the equator so that the Coriolis force can start the rotation; a pre-existing low pressure disturbance; high humidity in the lower atmosphere; and little change of wind with height (low vertical wind shear). Warm moist air rises, water vapour condenses and releases latent heat, the air rises faster, pressure at the surface falls further and more air is drawn in. The cyclone is a heat engine fed by latent heat, which is why it dies quickly once it crosses land and its fuel is cut off.

Structure. At the centre is the eye, 20–50 km wide, calm, clear and with the lowest pressure. Around it is the eye wall, a ring of towering clouds with the strongest winds and heaviest rain. Beyond are spiral rain bands. In the northern hemisphere the winds rotate anticlockwise. A Bay of Bengal cyclone is typically 300–600 km across.

Seasons in the Bay of Bengal. Two peaks: the pre-monsoon months of April–May (Aila, Fani, Amphan) and the post-monsoon months of October–November (the 1999 Odisha super-cyclone, Bulbul). The India Meteorological Department classifies storms from depression to deep depression, cyclonic storm, severe, very severe, extremely severe and super cyclonic storm (winds above 222 km/h).

Effects. Three agents cause the damage. Wind flattens houses, uproots trees and snaps electric poles. Rain causes floods and landslides. The storm surge — a wall of sea water pushed ashore by the wind and low pressure, 3–10 m high — is the biggest killer; it drowns the low islands of the Sundarbans, breaches the embankments and leaves salt in the fields for years. Cyclone Aila (25 May 2009) breached about 400 km of embankments in the Sundarbans, killed about 150 people in West Bengal and made farmland saline for three seasons. Amphan (20 May 2020) was even stronger, with winds over 150 km/h in Kolkata.

Management. Cyclones can be tracked by satellite and radar for days before landfall, so warning is the key. The IMD issues four-stage warnings; the state runs evacuation to cyclone shelters — raised concrete buildings that double as schools; embankments are strengthened; mangroves are planted as a living wall that breaks the surge; and fishermen are stopped from going to sea. The 1999 Odisha cyclone killed about 10,000 people; because of shelters and evacuation, Phailin in 2013, of similar strength, killed fewer than 50.

A drought is a prolonged period of abnormally low rainfall that leads to a shortage of water for crops, animals and people. It is a slow-onset disaster: it does not arrive in a night like a cyclone, but builds up over weeks and months, and its damage — crop failure, hunger, migration — spreads over years. In India, drought is declared when rainfall in a region is less than 75 per cent of the long-term average.

Types of drought.

• Meteorological drought — rainfall well below normal for the season. This is the starting point.
• Hydrological drought — rivers, ponds, reservoirs and groundwater fall below their normal levels because the rain has failed for long enough.
• Agricultural drought — soil moisture is too little for crops at the time they need it, so yields fall or the crop fails. This can happen even with normal total rainfall if the rain comes at the wrong time.
• Socio-economic drought — the shortage of water and food begins to affect people's livelihood, leading to unemployment, rising prices, sale of cattle and migration; in extreme cases, famine.

Causes. The basic cause is the failure or weakness of the south-west monsoon, often linked to El Niño years in the Pacific. Long breaks in the monsoon, late onset or early withdrawal have the same effect. Human causes make it worse: deforestation reduces the soil's ability to hold water; over-pumping of groundwater for boro paddy lowers the water table; the silting of tanks and ponds removes storage; and the cultivation of water-hungry crops in dry areas.

Drought in West Bengal. Though the state as a whole is wet, its western plateau fringe — Purulia, Bankura, western Bardhaman and Birbhum — lies in the rain shadow of the Chota Nagpur plateau, receives about 1,100–1,300 mm but very unevenly, and has thin lateritic soil over hard rock that stores almost no water. Streams like the Kangsabati and Silabati dry up in summer. Every third or fourth year the aman crop suffers, and villagers migrate to Bardhaman and Hooghly as harvest labour.

Effects. Crop failure and fodder shortage; death and distress sale of cattle; fall in farm employment and income; rise in food prices; drying of wells and long walks for water; malnutrition and disease; drop in hydroelectric generation; forest fires; and out-migration that empties villages.

Management. Drought cannot be prevented but can be planned for. Water harvesting — check dams, percolation tanks, farm ponds and the traditional bandhs of Bankura hold monsoon water; watershed development treats a whole catchment with contour bunding, trenching and afforestation; drought-resistant crops such as millets, pulses and short-duration paddy; drip and sprinkler irrigation; canals from the Kangsabati and Mayurakshi reservoirs; employment schemes such as MGNREGA that give wages for building water structures; fodder banks and cattle camps; crop insurance; and early warning from the IMD's monsoon forecasts.

A tsunami (Japanese: harbour wave) is a series of very long ocean waves produced by the sudden displacement of a large volume of sea water. It is often wrongly called a tidal wave, but it has nothing to do with tides. Its usual cause is a large undersea earthquake at a subduction zone in which the sea floor is suddenly thrust up or dropped down by several metres, lifting the whole column of water above it. Undersea volcanic eruptions, underwater landslides and, rarely, meteorite impacts can also cause them.

Behaviour at sea. In deep water a tsunami is almost invisible: its height is less than a metre, but its wavelength is 100–200 km and its speed is that of a jet aircraft, 700–900 km per hour, given by the formula speed = square root of (gravity × depth). Ships at sea do not notice it pass. As the wave enters shallow coastal water it slows down sharply, its wavelength shortens and its energy is squeezed into a smaller volume, so the height grows to 10 m, 20 m or more. The first sign on the shore is often a sudden withdrawal of the sea, exposing the sea bed, followed minutes later by the wall of water. A tsunami is not one wave but several, arriving ten to forty minutes apart, and the second or third is often the largest.

The 2004 Indian Ocean tsunami. On 26 December 2004 at 6:29 a.m. Indian time a magnitude 9.1 earthquake occurred off the west coast of northern Sumatra, where the Indian plate slides under the Burma micro-plate. About 1,300 km of fault ruptured and the sea floor rose by several metres. Waves reached Sumatra within 20 minutes, the Andaman and Nicobar Islands and Thailand within an hour, the Tamil Nadu and Sri Lankan coasts in about two hours, and East Africa after seven hours. About 2.3 lakh people died in 14 countries; in India about 10,750 died, chiefly in Tamil Nadu (Nagapattinam), Andhra Pradesh, Kerala, Puducherry and the Nicobar Islands, where Car Nicobar and Katchal were devastated. Fishing villages were wiped out, and boats, nets and fields were lost. There was no warning system in the Indian Ocean at that time.

Effects. Drowning; destruction of coastal houses, ports and roads; salt contamination of soil and wells; loss of fishing boats and livelihoods; erosion of beaches; and long-term trauma.

Management. After 2004 India built the Indian Tsunami Early Warning Centre at INCOIS, Hyderabad (2007), with sea-bottom pressure sensors and tide gauges that can issue a warning within 10–20 minutes of an earthquake. Other measures are coastal hazard maps, evacuation routes to high ground, bio-shields of mangroves and casuarina, sea walls at critical points, keeping buildings back from the shore under Coastal Regulation Zone rules, and public education: if the sea suddenly withdraws or a strong earthquake is felt near the coast, run inland or to high ground at once.

Man-made (anthropogenic) disasters are caused by human error, negligence, greed or violence rather than by natural forces. They are, in theory, the most preventable of all disasters, because the cause lies within human control. The chapter groups them into a few important kinds.

Fire. Fire is the most frequent man-made disaster in West Bengal's crowded cities. Causes are short circuits in old wiring, illegal electric connections, cooking fires in slums, storage of inflammable goods, and blocked fire exits. The Stephen Court fire in Park Street, Kolkata, in March 2010 killed 43 people because the building's stairways were blocked and the fire escape was locked. The AMRI hospital fire in Dhakuria in December 2011 killed about 90 patients when smoke from a basement full of inflammable stores spread through the wards. Prevention means fire audits, working extinguishers and hydrants, clear exits, smoke alarms, fire drills, and a fire brigade that can reach a building through wide enough lanes.

Industrial accidents. The worst in world history was the Bhopal gas tragedy of the night of 2–3 December 1984, when about 40 tonnes of methyl isocyanate leaked from the Union Carbide pesticide plant. Safety systems had been shut down to save money. About 3,800 people died within days and more than 15,000 over the years; over five lakh were injured. It led to the Environment Protection Act of 1986 and rules on hazardous industries. Other examples are the Vizag styrene gas leak of 2020 and frequent boiler explosions and factory fires in Howrah and Haldia.

Nuclear accidents. The Chernobyl reactor explosion in Ukraine (1986) spread radioactive dust across Europe and made a zone of 30 km uninhabitable to this day; the Fukushima accident in Japan (2011) followed a tsunami that flooded the reactor's cooling pumps. Radiation causes cancers and genetic damage for decades. Safety demands multiple cooling systems, containment buildings and siting away from earthquake and tsunami zones.

Transport accidents. Rail accidents such as Gaisal (Assam, 1999, about 290 dead) and Jnaneswari Express (West Midnapore, 2010, 148 dead, caused by sabotage of the track); air crashes; and the Bagmati river bus and boat disasters. Poor maintenance, over-crowding and human error are the usual causes.

Structural collapses. The Vivekananda Road flyover collapse in Kolkata in March 2016 killed 27 people; the Majerhat bridge collapse in 2018 killed 3. Poor materials, poor design and lack of inspection lie behind them.

Others. Stampedes at religious gatherings; riots and terrorist attacks; oil spills; chemical contamination of rivers; and, at the largest scale, war.

Management. Strict enforcement of building, fire and factory laws; regular inspections; safety training; on-site and off-site emergency plans for hazardous factories; mock drills; and punishment of negligence. Because these disasters are preventable, prevention rather than relief is the correct focus.

Disaster management means the planned and coordinated effort to reduce the risk of disasters, to respond effectively when they strike, and to help the community recover afterwards. Modern thinking sees it not as a single act of relief after the event but as a continuous cycle with three phases that flow into one another.

1. Pre-disaster phase (before the event). This is the most important phase because every rupee spent here saves many rupees of relief later. It has three parts.

• Prevention — stopping the hazard from happening at all where that is possible: fire safety rules, safe factories, embankments on rivers, afforestation on slopes.
• Mitigation — reducing the damage when the hazard cannot be stopped: earthquake-resistant buildings, cyclone shelters, flood-plain zoning, mangrove planting, hazard maps, insurance.
• Preparedness — getting ready to act: early-warning systems, evacuation plans and routes, stocks of food, water and medicine, trained volunteers, school drills, awareness campaigns and lists of vulnerable people such as the old, the sick and the disabled.

2. During-disaster phase (response). The aim here is to save lives and limit damage in the hours and days of the event. Steps are: issuing the final warning and ordering evacuation; search and rescue; first aid and moving the injured to hospital; providing shelter, drinking water, food, clothing and sanitation in relief camps; restoring communication so that help can be coordinated; and keeping law and order. The first 72 hours are called the golden period for rescue.

3. Post-disaster phase (after the event). This has two stages. Recovery or rehabilitation is the short term: repairing houses, roads, electricity and water supply; restarting schools and markets; medical care and counselling; giving seeds, tools, boats or cattle so that families can earn again; and compensation. Reconstruction is the long term: rebuilding to safer standards, moving settlements out of the most dangerous sites and reviewing what went wrong so that the next pre-disaster phase is better. In this way the cycle closes: the lessons of one disaster become the mitigation of the next.

Two older approaches. The traditional approach was relief-centred: the government waited for the disaster and then distributed food and money. The modern approach, adopted in India after the 1999 Odisha cyclone and the 2001 Bhuj earthquake, is risk-reduction-centred: it treats disaster management as part of development planning and puts most of the effort before the event. The Disaster Management Act of 2005 made this the law.

Vulnerability mapping is the tool that connects the phases. A vulnerability map shows which areas and which groups face the greatest risk from each hazard, so that shelters, warnings and building rules can be targeted. The Vulnerability Atlas of India maps every district for earthquake, wind and flood risk.

Until the beginning of this century India managed disasters through the Relief Commissioner of each state and the Ministry of Agriculture at the centre, treating every event as a relief problem. The Odisha super-cyclone of 1999, the Bhuj earthquake of 2001 and the tsunami of 2004 showed that this was not enough. Parliament passed the Disaster Management Act, 2005, which created a three-tier structure.

National level. The National Disaster Management Authority (NDMA), headed by the Prime Minister, lays down policy, plans and guidelines for every kind of disaster. The National Executive Committee, headed by the Union Home Secretary, carries them out. The National Disaster Response Force (NDRF) is a specially trained force of sixteen battalions drawn from the central police forces, equipped for search, rescue and relief in collapsed buildings, floods, chemical leaks and radiation; a battalion is based near Kolkata at Haringhata, Nadia. The National Institute of Disaster Management (NIDM) in Delhi trains officials and does research. The India Meteorological Department warns of cyclones, heavy rain and heat waves; the Central Water Commission forecasts floods; the Geological Survey of India maps landslide and earthquake hazards; and INCOIS, Hyderabad, issues tsunami warnings.

State level. Every state has a State Disaster Management Authority (SDMA) headed by the Chief Minister, with a State Executive Committee headed by the Chief Secretary. West Bengal has a separate Department of Disaster Management and Civil Defence, a state disaster management plan, and a state response force. It maintains cyclone shelters along the coast, flood shelters in the delta districts, and relief godowns in each district.

District level. The District Disaster Management Authority (DDMA) is chaired by the District Magistrate, who is the key officer in any actual emergency: he or she orders evacuation, opens relief camps, calls in the NDRF and army, and distributes relief. Below the district, the Block Development Officer and the gram panchayat maintain lists of vulnerable people, run the village task forces and manage the shelters. In the Sundarbans, village volunteers trained by the Red Cross run the warning flags and loudspeakers when a cyclone approaches.

Funds. The National Disaster Response Fund and the State Disaster Response Fund pay for relief; mitigation funds pay for shelters, embankments and training.

Non-government bodies. The Indian Red Cross Society, Ramakrishna Mission, Bharat Sevashram Sangha and many local organisations do rescue, run kitchens and rebuild houses. International bodies such as the UN Office for Disaster Risk Reduction (UNDRR) coordinate world effort; the Sendai Framework 2015–2030 sets global targets for reducing disaster deaths and losses. India also has a National Disaster Management Plan (2016) aligned with the Sendai Framework, and observes 29 October as National Disaster Reduction Day, while 13 October is the International Day for Disaster Risk Reduction.

Governments and trained forces cannot be everywhere at once. In the first hours of any disaster the people who save the most lives are neighbours, family members and local volunteers. This is why the modern approach is called community-based disaster management: the community that faces the hazard is trained and equipped to be the first responder.

The community. A village or ward can form a disaster management committee and task forces for early warning, evacuation, search and rescue, first aid, and relief camp management. It should keep a hazard map of its area showing safe routes and shelters, a list of people needing help, and a stock of ropes, torches, boats and first-aid boxes. Traditional knowledge matters: fishermen who read the sky, farmers who know which fields drain last, elders who remember where the 1978 flood water reached. Mock drills once a year keep the plan alive. After a disaster, the community rebuilds together and holds the authorities to their promises.

The family. Every family should have an emergency kit: dry food for three days, drinking water, a torch with batteries, a battery radio, a first-aid box with essential medicines, candles and matches, copies of important documents (ration card, land papers, school certificates) in a waterproof bag, and some cash. The family should agree on where to meet if separated, know the nearest shelter and the route to it, and keep the mobile charged when a warning is issued. Houses in cyclone areas should have their roofs tied down and in flood areas a raised platform for grain and cattle. The elderly and the very young must be moved first.

The student. Students are the best agents of awareness because they carry what they learn into every home. A student can:

• Learn the correct actions for each hazard — Drop, Cover and Hold in an earthquake; move to high ground in a flood or tsunami; stay indoors away from windows in a cyclone; use the stairs and stay low under smoke in a fire.
• Take part in the school's safety drills and help make the school disaster plan and hazard map.
• Learn first aid and how to make oral rehydration solution.
• Teach the family about warning signals and the emergency kit.
• Volunteer with the NCC, NSS, Scouts and Guides or the Red Cross Junior Wing in relief work.
• Practise the habits that reduce risk: not blocking drains with plastic, planting trees, not wasting water, reporting exposed wires.

Emergency numbers. In India the single emergency number is 112; the fire brigade is 101, ambulance 102 and 108, police 100, and disaster helpline 1070 (state) and 1077 (district). Knowing these numbers by heart is itself a preparedness measure.

The message of the chapter is simple: hazards are natural, but disasters are made by unpreparedness. A prepared community, family and student turn a potential catastrophe into an event that is survived and recovered from.