Disaster Management (CS-703 (D)) - Unit 5 Short Notes

How unit 5 is examined

This unit applies disaster management to real hazards; the marks sit in fluvial and pluvial flooding, man-made disaster case studies (Bhopal) and earthquake vulnerability assessment.

Landslide Hazard Zonation: Case Studies

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Definition. <mark>Landslide hazard zonation (LHZ) divides a hilly area into zones of very low to very high landslide hazard, according to the causative factors present on each part of the slope.</mark>

Key points.

1. LHZ maps are prepared from causative factors: lithology, geological structure, slope angle, relative relief, land use and land cover, drainage, and rainfall.
2. Each factor class is given a rating and each factor a weight, and the summed Landslide Hazard Evaluation Factor (LHEF) rating classifies the slope into five zones from very low to very high hazard (BIS IS 14496).
3. Satellite images, DEMs and GIS are used to overlay the layers, and field checks confirm the map.
4. Case studies are the Himalayan belt and Western Ghats, for example Kedarnath (2013), Malin in Pune (2014) and Kerala (2018).

Earthquake Vulnerability Assessment of Buildings and Infrastructure: Case Studies

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Definition. <mark>Earthquake vulnerability assessment estimates how much damage a building or infrastructure element will suffer for a given shaking intensity.</mark>

Key points.

1. Vulnerability assessment shows which buildings, bridges, hospitals and lifelines are weak, so limited money goes to the most dangerous ones first.
2. Rapid Visual Screening (RVS, for example FEMA 154) scores a building from the street on storeys, soft storey, irregularity, material, age and soil, and flags those needing detailed study.
3. Detailed analysis uses structural calculation against the code (IS 1893, IS 13920), non-destructive tests and fragility curves.
4. Assessment reduces structural and non-structural damage, guides retrofitting (IS 13935), supports land-use planning and insurance, and makes new construction safer.
5. The 2001 Bhuj earthquake, where poorly built reinforced concrete and masonry buildings collapsed, is the standard Indian case.

Answer frame. Open with the definition; then develop points 1-4 in order, naming RVS, codes and retrofitting as methods; close with the Bhuj 2001 lesson that assessment before a quake saves lives.

Building assessment methods (for the short note). RVS first, then detailed evaluation, then retrofitting of the weak buildings.

Asked: [7 marks] (Dec 2020) Describe the importance of Vulnerability assessment of Buildings and Infrastructure. Asked: [14 marks, any two of three] (Jun 2025) Short note: Earthquake Vulnerability assessment of Buildings.

Drought Assessment: Case Studies

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Definition. <mark>Drought is a prolonged period of abnormally low rainfall that causes a shortage of water for people, crops and ecosystems.</mark>

Key points.

1. Types are meteorological (rainfall deficit), hydrological (low river and groundwater levels), agricultural (soil moisture stress) and socio-economic.
2. IMD calls a season a drought year when the all-India rainfall deficit exceeds 10 percent of normal, and severe when the deficit exceeds 50 percent in an area.
3. Indices used are the Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI) and the satellite Normalized Difference Vegetation Index (NDVI).
4. Case studies are the 2002, 2009 and 2014-15 Indian droughts and the Marathwada and Bundelkhand droughts.

Coastal Flooding: Storm Surge Assessment

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Definition. <mark>A storm surge is the abnormal rise of sea level above the normal tide, caused by the strong winds and low pressure of a cyclone pushing water onto the coast.</mark>

Key points.

1. Surge height depends on wind speed, central pressure drop, the slope of the sea bed and the angle of landfall, and it is worst when it coincides with high tide.
2. Assessment uses numerical models such as SLOSH, together with coastal elevation maps, to draw inundation zones for each cyclone category.
3. The 1999 Odisha super cyclone produced a surge of about 7 metres and killed roughly 10,000 people; the 2013 Phailin cyclone killed far fewer because of early warning and evacuation.
4. Mitigation is early warning by IMD, cyclone shelters, embankments, mangrove belts and coastal regulation zones.

Floods: Fluvial and Pluvial Flooding: Case Studies

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Definition. <mark>A flood is the overflow of water onto land that is normally dry; fluvial flooding is caused by rivers overflowing their banks, and pluvial flooding is caused by intense rainfall exceeding local drainage capacity.</mark>

Key points.

1. Fluvial (river) flooding occurs when a river receives more water than its channel holds, from heavy upstream rain, snowmelt, dam release or breach of an embankment.
2. Pluvial (surface-water) flooding occurs where the rain falls, when the rainfall intensity is higher than the soil can absorb or the drains can carry away, and it does not need any river to overflow.
3. Fluvial floods rise slowly, are predictable from upstream gauges, and last days or weeks; pluvial floods are sudden, local and short, and give little warning.
4. Causes of pluvial flooding in cities are paved surfaces, encroached and choked drains, poor solid waste management and loss of wetlands.
5. Causes of fluvial flooding are cloudburst or monsoon rain in the catchment, deforestation, siltation of the river bed, and reduced floodplains.
6. Indian case studies: the Kosi flood of Bihar (2008) after an embankment breach, the Uttarakhand flood (2013), Chennai (2015) and Kerala (2018) floods, and Mumbai (2005), which is the standard urban pluvial case.
7. Management uses flood forecasting, embankments and dams, floodplain zoning, urban drainage and rainwater storage, and community evacuation plans.

COVID-19 (short note, if chosen). COVID-19 is a pandemic disease caused by the SARS-CoV-2 virus, first reported in Wuhan in December 2019. It spreads by respiratory droplets and close contact. Management was testing, isolation, lockdown, masks, social distancing and vaccination.

Answer frame. Open with the definition of both types; draw nothing, or a simple river and city sketch; give the comparison table, then causes (points 4-5), then a case study each; close with management. For a short note choose fluvial and pluvial plus one other, since only two are required.

Asked: [14 marks, any two of three] (Jun 2025) Short notes: a) Fluvial and Pluvial Flooding b) COVID-19 c) Earthquake Vulnerability assessment of Buildings.

Forest Fire: Case Studies

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Definition. <mark>A forest fire is an uncontrolled fire that spreads through forest vegetation, started by natural causes such as lightning or by human activity.</mark>

Key points.

1. Causes are lightning and dry weather, but most Indian fires are human: cleared land burning, carelessly dropped cigarettes and campfires, and grazing practices.
2. Spread depends on fuel (dry leaves, pine needles), weather (heat, low humidity, wind) and slope, with fire moving faster uphill.
3. Satellite sensors such as MODIS and VIIRS give fire alerts, and the Forest Survey of India runs a fire alert system.
4. Case studies are Uttarakhand (2016) and Simlipal in Odisha, and abroad Australia (2019-20) and California.

Man Made disasters: Case Studies

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Definition. <mark>Man-made disasters are disasters caused by human negligence, error or intent, unlike natural disasters, which arise from nature's forces such as earthquake and cyclone.</mark>

Key points.

1. Industrial disasters are chemical leaks, explosions and fires in factories, for example Bhopal gas tragedy (1984) and Vizag LG Polymers leak (2020).
2. Transport disasters are road, rail, air and ship accidents.
3. Nuclear and radiological disasters are reactor accidents, for example Chernobyl (1986) and Fukushima (2011).
4. Terrorist and war-related disasters are bombings and attacks, for example the Mumbai attacks (2008).
5. Environmental disasters include oil spills and river pollution.
6. Structural and fire disasters include building collapses and crowd stampedes.

Case study: Bhopal gas tragedy.

1. Background: on the night of 2-3 December 1984 at the Union Carbide pesticide plant, Bhopal, about 40 tonnes of methyl isocyanate (MIC) gas leaked.
2. Causes: water entered an MIC storage tank and started a violent reaction, and the safety systems (refrigeration, scrubber, flare tower) were not working, with poor maintenance and training.
3. Impact: thousands died within days (about 3,800 immediately by some estimates, far more later), more than 500,000 were exposed, with lung, eye and neurological illness and birth defects, cattle and crop loss, and lasting soil and water contamination.
4. Lessons: strict safety audits, a buffer zone between plants and homes, emergency plans and public warning, right-to-know laws, and the Environment Protection Act 1986 and Public Liability Insurance Act 1991.

Answer frame. For the case study, open with Bhopal, draw nothing, then develop background, causes, impact, lessons in order, and close with the lesson that prevention is cheaper than cure. For "what do you mean", open with the definition against natural disasters, give the classification list, then two examples.

Asked: [7 marks] (Dec 2020) Give a case study of man made disasters. Asked: [7 marks] (Jun 2025) What do you mean by Man Made disasters? Give some suitable examples.

Space Based Inputs for Disaster Mitigation and Management and field works related to disaster management

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Definition. <mark>Space-based inputs are satellite data from remote sensing, communication and navigation satellites that support disaster mitigation, early warning, response and damage assessment.</mark>

Key points.

1. Remote sensing satellites (Cartosat, Resourcesat, RISAT radar which sees through cloud) map hazard zones and flooded areas and assess damage.
2. Weather satellites (INSAT, INSAT-3D) track cyclones and monsoon rain for forecasts.
3. Communication satellites keep links working when ground networks fail, and navigation (NavIC, GPS) guides rescue.
4. ISRO's Decision Support Centre and the Bhuvan portal deliver flood, fire and landslide maps to authorities.
5. Field work includes hazard surveys, vulnerability and capacity mapping with the community, mock drills, and post-disaster damage surveys.

Last-minute revision

• Man-made disasters arise from human negligence or intent; natural ones from nature.
• Bhopal: 2-3 Dec 1984, Union Carbide, MIC gas leak, water entered the tank, safety systems failed.
• Chernobyl 1986 and Fukushima 2011 are nuclear disasters.
• Fluvial flood is river overflow, slow and predictable; pluvial flood is rain exceeding drainage, sudden and local.
• Kosi 2008 was fluvial; Mumbai 2005 was pluvial.
• Rapid Visual Screening (FEMA 154) is the first step of building vulnerability assessment; retrofitting follows (IS 13935).
• Bhuj 2001 is the earthquake vulnerability case.
• Storm surge is a cyclone-driven rise in sea level; Odisha 1999 surge was about 7 m.
• IMD drought: rainfall deficit above 10 percent; indices SPI, PDSI, NDVI.
• LHZ uses lithology, slope, relief, land use, drainage and rainfall to grade five hazard zones.
• COVID-19: SARS-CoV-2 pandemic from December 2019, managed by isolation, lockdown and vaccination.

Memory hooks

• Bhopal = "MIC plus water plus broken safety".
• Fluvial = river, Pluvial = pour (rain on the spot).
• RVS = look first, calculate later, retrofit last.
• Man-made classes: I-T-N-T-E (Industrial, Transport, Nuclear, Terror, Environmental).
• Surge worst at landfall plus high tide.

Coverage checklist

• Landslide Hazard Zonation: Case Studies (no past question)
• Earthquake Vulnerability Assessment of Buildings and Infrastructure: Case Studies (Dec 2020 importance; Jun 2025 short note c)
• Drought Assessment: Case Studies (no past question)
• Coastal Flooding: Storm Surge Assessment (no past question)
• Floods: Fluvial and Pluvial Flooding: Case Studies (Jun 2025 short note a, b)
• Forest Fire: Case Studies (no past question)
• Man Made disasters: Case Studies (Dec 2020 case study; Jun 2025 meaning and examples)
• Space Based Inputs for Disaster Mitigation and Management and field works related to disaster management (no past question)