Disaster management

Environmental Science (B.Sc) · Environmental management · free study notes for exams, placements and interviews

In short

Disaster management is the organised cycle of preventing, preparing for, responding to and recovering from events — natural or human-made — that cause damage beyond the coping capacity of the affected community. India is among the most disaster-prone countries: about 59% of its land is earthquake-prone, 12% flood-prone, and its 7,500+ km coastline faces cyclones and tsunami, so the subject sits at the centre of environmental management practice. It is examined in B.Sc/M.Sc Environmental Science, AICTE's mandatory Disaster Management course, UGC CBCS Environmental Studies, and in UPSC/state PSC and GATE-ES style papers. Employers who test it include NDMA and SDMAs, district administrations, NDRF, UNDP/UNICEF/SEEDS and other NGOs, insurance and reinsurance risk teams, EHS and business-continuity cells of manufacturing and IT firms, and consultancies preparing District Disaster Management Plans.

Explained

Core definitions and the risk equation

Hazard: a potentially damaging physical event, phenomenon or human activity (an earthquake, a cyclone, a chlorine leak). A hazard alone is not a disaster.
Vulnerability: conditions — physical, social, economic, environmental — that make a community susceptible to a hazard (kutcha housing, poverty, old age, no information access).
Exposure: the people, property, infrastructure and ecosystems located in hazard-prone areas.
Capacity / coping capacity: resources, skills and institutions available to resist or recover. Resilience is the ability to absorb, adapt and bounce back.
Disaster (DM Act, 2005 definition): a catastrophe, mishap, calamity or grave occurrence from natural or man-made causes causing substantial loss of life, destruction of property or damage to the environment, of such magnitude as to be beyond the coping capacity of the community.
Risk is the expected loss: conceptually Risk = Hazard × Vulnerability ÷ Capacity, or Risk = Hazard (probability) × Exposure × Vulnerability.
Disaster Risk Reduction (DRR): reducing risk by lowering vulnerability and exposure rather than by waiting to respond. Mitigation reduces impact (structural and non-structural); preparedness readies the response.

Classification of disasters

Natural — geophysical: earthquakes, tsunami, landslides, volcanic activity, avalanches.
Natural — hydro-meteorological: floods, flash floods, cloudbursts, cyclones, storm surges, hailstorms, lightning, heat waves, cold waves, droughts, glacial lake outburst floods (GLOFs).
Natural — biological: epidemics and pandemics, pest attacks, locust swarms.
Human-induced / technological: industrial and chemical accidents (Bhopal 1984), fires, building collapse, mine accidents, oil spills, nuclear and radiological events, road/rail/air accidents, dam bursts, stampedes.
Human-induced / conflict: CBRN (chemical, biological, radiological, nuclear) events, terrorism, bomb blasts, cyber attacks on critical infrastructure.
By onset: rapid-onset (earthquake, flash flood) versus slow-onset/creeping (drought, desertification, sea-level rise, climate change impacts).
NDMA groups hazards for planning into natural and man-made, and the Ministry of Home Affairs lists notified calamities eligible for SDRF/NDRF funding (cyclone, drought, earthquake, fire, flood, tsunami, hailstorm, landslide, avalanche, cloudburst, pest attack, frost and cold wave).

The disaster management cycle

Prevention: eliminating risk at source — zoning that forbids construction in a floodway, banning a hazardous process in a dense area.
Mitigation (pre-disaster): structural — embankments, cyclone shelters, retrofitting, check dams, seismic design to IS 1893; non-structural — land-use regulation, building bye-laws, insurance, awareness, ecosystem buffers (mangroves, sand dunes).
Preparedness: plans, early warning systems, mock drills, stockpiles, trained task forces, evacuation routes, resource inventories (IDRN — India Disaster Resource Network).
Response (immediate): search and rescue, evacuation, first aid, incident command, debris clearance, restoring lifelines, relief camps, water and sanitation, dead body management.
Recovery / rehabilitation: restoring services and livelihoods; reconstruction under "build back better" with safer standards.
The pre-disaster phase (1-3) is where money is best spent; studies routinely find mitigation returns several rupees of avoided loss per rupee spent, and the Sendai Framework shifted global emphasis from response to risk reduction.

India's legal and institutional framework

Disaster Management Act, 2005: the governing statute. Creates a three-tier structure and makes DM planning a statutory duty of every ministry and department. It was amended in 2025 (Disaster Management (Amendment) Act) to give statutory status to the National Crisis Management Committee and High Level Committee, strengthen plan-making by NDMA/SDMA, and provide for urban disaster management authorities in large cities and for state disaster response forces — check the current amended text, as rules and notified provisions are still being operationalised.
NDMA (National Disaster Management Authority): chaired by the Prime Minister; lays down policies, plans and guidelines; approves the National Plan.
NEC (National Executive Committee): Union Home Secretary as chair; prepares the National Plan and coordinates implementation.
SDMA: chaired by the Chief Minister; DDMA: chaired by the District Collector/District Magistrate with the elected district panchayat head as co-chair — the DDMA is the key operational unit and prepares the District Disaster Management Plan.
NIDM (National Institute of Disaster Management): training, research, documentation and capacity building.
NDRF: a specialist multi-disciplinary force (16 battalions, drawn from CAPFs) for specialised response; states raise SDRF units.
Funding: National Disaster Response Fund (NDRF, fund) and State Disaster Response Fund (SDRF, fund) for relief; National and State Disaster Mitigation Funds for mitigation; allocations follow Finance Commission recommendations (15th FC set a 20:80 mitigation:response split within the overall award — verify current 16th FC position).
Related laws: Environment (Protection) Act, 1986 and the Chemical Accidents (Emergency Planning, Preparedness and Response) Rules, 1996 (crisis groups at central, state, district and local level); Manufacture, Storage and Import of Hazardous Chemical Rules, 1989 (on-site and off-site emergency plans, MAH units); Public Liability Insurance Act, 1991 (no-fault relief); National Green Tribunal Act, 2010; Epidemic Diseases Act, 1897 (as amended 2020); the SHANTI Act, 2025 (which replaced the Atomic Energy Act, 1962 and the Civil Liability for Nuclear Damage Act, 2010) for nuclear and radiological events. Occupational safety duties formerly under the Factories Act, 1948 now sit in the Occupational Safety, Health and Working Conditions Code, 2020, in force with the other three Labour Codes from 21 November 2025.
Plans and guidelines: National Disaster Management Plan (NDMP) 2016, revised 2019, aligned to the Sendai Framework's four priorities and its themes of prevention, mitigation, response and recovery; NDMA hazard-specific guidelines (earthquake, flood, cyclone, chemical, urban flooding, heat wave, landslide, school safety).

Warning agencies, codes and risk mapping in India

IMD: cyclone warnings (four-stage system — pre-cyclone watch, cyclone alert, cyclone warning, post-landfall outlook), heavy rainfall and heat-wave warnings with the colour code green/yellow/orange/red; doppler weather radar network.
CWC (Central Water Commission): flood forecasting at level and inflow forecast stations; GSI for landslides; NCS (National Centre for Seismology) for earthquake monitoring; INCOIS, Hyderabad hosts the Indian Tsunami Early Warning Centre; SASE for avalanches; NRSC/ISRO for satellite-based damage assessment; SACHET / Common Alerting Protocol for location-based warning SMS.
Seismic zoning (IS 1893-1:2016, Part 1): Zones II, III, IV and V with zone factors Z = 0.10, 0.16, 0.24 and 0.36 respectively; Zone V (Kutch, Andaman & Nicobar, parts of Himachal, Uttarakhand, North-East, north Bihar) is the most severe. The old Zone I was merged into Zone II.
Other codes: IS 13920 (ductile detailing of RC structures), IS 4326 (earthquake-resistant design and construction of buildings), IS 13828 (low-strength masonry), IS 13935 (repair, restoration and seismic strengthening/retrofitting), National Building Code of India 2016 (Part 4 fire and life safety).
Vulnerability Atlas of India (BMTPC): state-wise maps and housing-stock risk tables for earthquake, cyclone, flood, landslide and thunderstorm.
Incident Response System (IRS): NDMA's adaptation of incident command — Responsible Officer, Incident Commander, and Operations, Planning, Logistics and Finance/Administration sections; unity of command, span of control, common terminology.

Assessment, response tools and the environmental link

HRVA (Hazard, Risk and Vulnerability Analysis): hazard identification → mapping and probability → exposure inventory → vulnerability assessment (physical, social, economic) → capacity analysis → risk ranking → mitigation plan. Basis of every District Plan.
Damage and loss assessment: rapid assessment within 24-72 hours; detailed PDNA (Post-Disaster Needs Assessment) for reconstruction financing; ICT tools — GIS, remote sensing, drones, GPS, mobile data collection, Bhuvan portal.
Relief standards: Sphere Standards and India's own norms — minimum 15 litres of water per person per day in camps (Sphere), nutrition, shelter space, sanitation ratios; SDRF items and norms notified by MHA.
Triage in mass-casualty events: red (immediate), yellow (delayed), green (minor), black (expectant/dead).
Industrial/EHS link: HAZOP, QRA, consequence modelling, on-site and off-site emergency plans, MSIHC Rules threshold quantities, mutual aid response groups, ERDMP for petroleum installations.
Environment and climate link: deforestation, wetland loss, unplanned urbanisation and encroached drains convert hazards into disasters; Eco-DRR uses mangroves, dunes and watersheds as buffers; climate change raises frequency and intensity of extreme events, which is why adaptation (SAPCC) and DRR plans are being integrated.
Limitations: forecasting skill falls sharply for earthquakes (no reliable prediction), cloudbursts and landslides; last-mile warning dissemination, plan quality at district level, and a persistent bias towards relief spending over mitigation remain weak points.

Key points

Disaster - a hazard event whose losses exceed the community's coping capacity; hazard + vulnerability, not hazard alone.
Risk equation - Risk = Hazard × Vulnerability ÷ Capacity; reduce vulnerability or raise capacity to cut risk.
DM Act, 2005 - India's governing statute; creates NDMA (PM), SDMA (CM), DDMA (Collector); amended in 2025.
NIDM - training and capacity building; NDRF - 16-battalion specialist response force; states have SDRF units.
Cycle - prevention, mitigation, preparedness, response, recovery/reconstruction; pre-disaster investment is the cheapest.
Structural vs non-structural mitigation - embankments and retrofitting versus zoning, bye-laws, insurance and awareness.
Sendai Framework 2015-2030 - 4 priorities, 7 global targets; successor to the Hyogo Framework; NDMP 2016/2019 aligns to it.
IS 1893-1:2016 - seismic zones II-V with Z = 0.10/0.16/0.24/0.36; about 59% of India's land is earthquake-prone.
IS 13920 / IS 4326 / IS 13935 - ductile detailing, earthquake-resistant construction, retrofitting of existing buildings.
Warning agencies - IMD (cyclone, heat, rain), CWC (floods), INCOIS (tsunami), NCS (earthquakes), GSI (landslides), SASE (avalanches).
IMD colour codes - green (no action), yellow (watch), orange (be prepared), red (take action).
IRS - Responsible Officer and Incident Commander with Operations, Planning, Logistics and Finance/Admin sections.
Funds - NDRF/SDRF for relief, National and State Mitigation Funds for mitigation, as per Finance Commission norms.
MSIHC Rules, 1989 and Chemical Accidents Rules, 1996 - on-site/off-site emergency plans and crisis groups for industry.
Public Liability Insurance Act, 1991 - no-fault immediate relief for victims of hazardous-substance accidents.
Triage colours - red immediate, yellow delayed, green minor, black expectant/dead.
Vulnerability Atlas of India (BMTPC) - the standard source for multi-hazard housing vulnerability data.
Build back better - reconstruction to safer standards, a Sendai priority and the core of recovery planning.

Formulas and examples

Risk R = H × V / C — H = hazard probability or intensity, V = vulnerability index (0-1), C = capacity index; R is dimensionless or in loss units
Expected Annual Loss EAL = Σ (Pᵢ × Lᵢ) — Pᵢ = annual exceedance probability of event i, Lᵢ = loss (₹) if it occurs; EAL in ₹/year
Return period T = 1/P — P = annual exceedance probability; probability of at least one event in n years = 1 − (1 − P)ⁿ
Earthquake magnitude energy: log₁₀E = 11.8 + 1.5 M — E in ergs, M = Richter magnitude; energy ratio for ΔM = 1 is 10^1.5 ≈ 31.6
Seismic design base shear (IS 1893-1:2016): V_B = A_h × W, with A_h = (Z/2)(Sa/g)/(R/I) — Z zone factor, Sa/g spectral acceleration, R response reduction factor, I importance factor, W seismic weight (kN)
Benefit-Cost Ratio BCR = (avoided losses, present value) / (mitigation cost, present value) — dimensionless; BCR > 1 justifies the measure
Rational formula for peak flood runoff Q = C i A / 3.6 — Q in m³/s, C runoff coefficient (0-1), i rainfall intensity in mm/h, A catchment area in km²
Relief planning: water demand = population × 15 litres/person/day (Sphere minimum in camps)

Example 1 — Return period and exposure. A town lies in a floodplain where the design flood has a return period of 50 years.

Annual exceedance probability P = 1/50 = 0.02.
Probability of at least one such flood in a 30-year mortgage period = 1 − (1 − 0.02)³⁰ = 1 − 0.98³⁰.
0.98³⁰ = e^{30 × ln0.98} = e^{30 × −0.020203} = e^−0.60609 = 0.5455.
Probability = 1 − 0.5455 = 0.4545, about 45%. A "50-year flood" is therefore close to a coin toss over a housing loan's life — the standard argument against treating a long return period as safety.

Example 2 — Expected annual loss and a mitigation BCR. A municipal ward has three flood scenarios:

Scenario	Annual probability P	Loss L (₹ crore)	P × L (₹ crore/yr)
Minor (2-year)	0.50	2	1.00
Moderate (10-year)	0.10	20	2.00
Severe (50-year)	0.02	150	3.00
EAL			6.00

EAL = 1.00 + 2.00 + 3.00 = ₹6 crore per year.
A storm-water drainage upgrade costs ₹40 crore and is expected to cut EAL by 60%, i.e. avoid ₹3.6 crore/year for a 25-year life.
Undiscounted avoided loss = 3.6 × 25 = ₹90 crore → BCR = 90/40 = 2.25.
At a 8% discount rate the annuity factor for 25 years = (1 − 1.08⁻²⁵)/0.08 = (1 − 0.14602)/0.08 = 10.675 → PV of benefits = 3.6 × 10.675 = ₹38.4 crore → BCR ≈ 0.96, marginally below 1. The lesson examiners look for: discounting matters, and mitigation economics must be stated with the rate and horizon used.

Example 3 — Earthquake energy comparison. Compare an M 6.0 event with the M 7.6 Bhuj earthquake (2001).

log₁₀E(7.6) − log₁₀E(6.0) = 1.5 × (7.6 − 6.0) = 1.5 × 1.6 = 2.4.
Energy ratio = 10^2.4 = 251. The Bhuj event released roughly 250 times the energy of an M 6.0 shock.
Amplitude ratio on a seismogram = 10^1.6 ≈ 40 times, which is why magnitude differences of "only" 1.6 change outcomes completely.

Example 4 — Seismic base shear for a school building. A 4-storey RC school in Guwahati (Zone V): seismic weight W = 9,000 kN, Sa/g = 2.5 (medium soil, short period), special moment-resisting frame R = 5, importance factor I = 1.5 (school/community building).

Z = 0.36 for Zone V → Z/2 = 0.18.
A_h = 0.18 × 2.5 / (5/1.5) = 0.45 / 3.333 = 0.135.
V_B = 0.135 × 9,000 = 1,215 kN.
In Zone III (Z = 0.16) the same building gives A_h = 0.08 × 2.5/3.333 = 0.060 and V_B = 540 kN — the Zone V demand is 2.25 times higher, exactly the ratio 0.36/0.16.

Example 5 — Relief camp planning. A cyclone evacuation moves 12,000 people into shelters for 7 days.

Drinking and domestic water at the Sphere minimum of 15 L/person/day = 12,000 × 15 = 180,000 L/day = 180 m³/day, i.e. 1,260 m³ for 7 days — about 23 tanker trips a day with a 8,000-litre tanker.
Toilets at 1 per 20 people = 12,000/20 = 600 units.
Food at 2,100 kcal/person/day = 25.2 million kcal/day; at roughly 500 g of dry ration per person per day, 12,000 × 0.5 × 7 = 42 tonnes for the week.

Phase	Timing	Typical actions	Lead agency in India
Mitigation	Continuous	Zoning, retrofitting, embankments, insurance	NDMA/SDMA, line departments, ULBs
Preparedness	Pre-season	Plans, drills, stockpiles, warning systems	DDMA, IMD/CWC, Civil Defence
Response	0-72 hours onward	Evacuation, search and rescue, relief camps	District Collector, NDRF/SDRF, IRS teams
Recovery	Weeks to years	PDNA, livelihoods, reconstruction	State government, line ministries, donors

Where it is used

District administration and SDMAs: preparing and updating District Disaster Management Plans, HRVA studies, mock drills and SDRF claims — roles such as District Project Officer (DM) and consultant under state DM projects.
Industry EHS and process safety: on-site and off-site emergency plans for MAH units under the MSIHC Rules, HAZOP and QRA studies, mutual aid groups in clusters like Dahej, Jamnagar, Manali (Chennai) and Taloja.
Infrastructure and construction: seismic design and retrofitting to IS 1893/IS 13920/IS 13935, fire and life safety under NBC 2016, dam safety under the Dam Safety Act, 2021 and emergency action plans.
Insurance, reinsurance and finance: catastrophe risk modelling, EAL and PML estimates, parametric crop and weather insurance under PMFBY, municipal resilience bonds.
Corporate business continuity and IT: BCP/DRP under ISO 22301 (business continuity) and recovery-site planning for banks and IT/BPO campuses in Chennai, Mumbai and Bengaluru.
Development and humanitarian sector: UNDP, UNICEF, IFRC/Indian Red Cross, SEEDS, Sphere India coordination; CSR-funded community resilience and cyclone-shelter projects in Odisha, Andhra Pradesh and Gujarat.
Documented Indian cases to cite: Bhopal gas tragedy 1984 (industrial), Odisha super cyclone 1999 versus Cyclone Fani 2019 (warning and evacuation improvement from about 10,000 deaths to double digits), Bhuj 2001, Indian Ocean tsunami 2004 (led to INCOIS warning centre), Uttarakhand 2013, Chennai floods 2015, Kerala floods 2018, Mumbai urban flooding.

Interview questions

Q: What is the difference between a hazard and a disaster? A: A hazard is the potentially damaging event; it becomes a disaster only when it strikes a vulnerable, exposed community and the losses exceed local coping capacity. A cyclone over empty sea is a hazard, not a disaster.
Q: Write the risk equation and explain how you would use it. A: Risk = Hazard × Vulnerability ÷ Capacity. Since hazard frequency is largely fixed, risk is managed by reducing vulnerability (retrofitting, zoning) and raising capacity (training, warning, funds).
Q: What three-tier structure does the DM Act, 2005 create? A: NDMA at national level chaired by the Prime Minister, SDMA in each state chaired by the Chief Minister, and DDMA in each district chaired by the Collector with the elected district panchayat head as co-chair; NEC, NIDM and NDRF support them.
Q: Which agency issues tsunami warnings for India and why was it set up? A: INCOIS, Hyderabad, through the Indian Tsunami Early Warning Centre, established after the 2004 Indian Ocean tsunami exposed the absence of any warning capability.
Q: Differentiate structural and non-structural mitigation with examples. A: Structural measures are physical works — embankments, cyclone shelters, seismic retrofitting; non-structural measures are policy and behaviour — land-use zoning, building bye-laws, insurance, early warning and community awareness.
Q: What are the seismic zones in India and the relevant code? A: IS 1893 (Part 1): 2016 defines Zones II to V with zone factors 0.10, 0.16, 0.24 and 0.36; Zone V includes Kutch, the Andaman and Nicobar Islands, north Bihar, parts of Uttarakhand, Himachal and the North-East.
Q: Why is a 100-year flood not a once-in-a-lifetime event? A: The return period is a statistical average; the annual probability is 1%, so over 50 years the chance of at least one such flood is 1 − 0.99⁵⁰ ≈ 39%.
Q: What is the Incident Response System and why did India adopt it? A: NDMA's incident command structure with a Responsible Officer, Incident Commander and Operations, Planning, Logistics and Finance/Administration sections; it gives unity of command, clear span of control and common terminology so multiple agencies can work together.
Q: What is the Sendai Framework and how does India's plan relate to it? A: The global DRR agreement for 2015-2030 with four priorities and seven targets, successor to the Hyogo Framework; the National Disaster Management Plan 2016 (revised 2019) is structured around its priorities.
Q: An industrial unit stores large quantities of chlorine. What emergency planning does Indian law require? A: As a major accident hazard installation under the MSIHC Rules, 1989 it must have an on-site emergency plan and supply information for the district off-site plan, with crisis groups under the Chemical Accidents Rules, 1996 and no-fault insurance under the Public Liability Insurance Act, 1991.
Q: Why did Odisha's cyclone deaths fall so sharply between 1999 and 2019? A: Better IMD forecasting and lead time, a network of cyclone shelters, an institutionalised evacuation protocol (over a million people moved before Fani) and trained community task forces — a case of preparedness, not reduced hazard.
Q: How does environmental degradation increase disaster risk? A: Loss of mangroves, wetlands, dunes and forest cover removes natural buffers against surges, floods and landslides, while encroachment on drains and floodplains raises exposure — which is why Eco-DRR and DRR-climate adaptation integration are now mainstream.
Q: What is "build back better"? A: Reconstructing after a disaster to higher, hazard-resistant standards with improved siting and services, so that the rebuilt asset is less vulnerable than the one lost — a Sendai priority embedded in India's recovery guidance.

Common mistakes

Treating hazard and disaster as synonyms, or writing the risk equation without capacity in the denominator.
Confusing the two NDRFs — the National Disaster Response Force (the force) and the National Disaster Response Fund (the money); name them fully in answers.
Quoting the DM Act, 2005 without noting the 2025 amendment, or citing the withdrawn seismic Zone I instead of the current four zones of IS 1893-1:2016.
Misreading return period as "it will happen once in 50 years" instead of an annual 2% probability — and so under-stating lifetime risk.
Writing only about response and relief and ignoring prevention, mitigation and recovery, which is where most marks and most real work lie.
Unit and scale slips: mixing litres with m³ in relief calculations, mm/h with m/s in the rational formula, and crore with lakh in loss figures.
Reciting a BCR without stating the discount rate and project life, which can flip the conclusion as in the drainage example above.
Attributing earthquake prediction capability to NCS or IMD — magnitude and location are reported after the event; reliable short-term prediction does not exist.