Skip to content

Case Studies: Floods, Nepal Quake, Oil Spills | ICSE 8

questionbuddy.in/icse/class-8/geography/natural-and-man-made-disasters/case-studies-floods-nepal-earthquake-and-oil-spills

GeographyICSE Class 8 · Natural and Man-made Disasters

Case Studies: Floods in Assam and Bihar, Nepal Earthquake and US Oil Spills (ICSE Class 8)

Updated 17 October 2026 · Draft, not yet fact-checked

Assam and Bihar floods come from heavy monsoon rain, silt-laden rivers (Brahmaputra, Kosi), flat land, deforestation and embankment breaches. The Nepal earthquake of 25 April 2015 (magnitude about 7.8) was caused by the Indian plate pushing under the Eurasian plate and killed nearly 9,000 people. Oil spills in US coastal waters, such as Deepwater Horizon (2010) and Exxon Valdez (1989), damaged marine life, coasts, fishing and tourism.

Understand Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills

1. Floods in Assam. *Causes:* very heavy monsoon rainfall; the Brahmaputra carries a huge load of sediment that raises its bed; the river is wide and braided; tributaries from the hills cause flash floods; bank erosion; deforestation in the catchment; breaches in embankments. *Effects:* floods almost every monsoon displace large numbers of people and destroy crops, houses and roads; erosion eats away land (the river island Majuli has lost much land); animals in Kaziranga National Park drown or are hit by vehicles while fleeing to higher ground. *Environment:* fertile silt is deposited, but erosion and waterlogging damage land and habitats.

2. Floods in Bihar. The Kosi, called the 'Sorrow of Bihar', often floods and shifts its course. In August 2008 it breached its embankment at Kusaha in Nepal and changed course, flooding large areas of north Bihar and affecting millions of people. *Causes:* heavy rain in Nepal and Bihar, a high sediment load, flat land and embankment failure. *Effects:* loss of life, crops, cattle and homes, disease, and people forced into relief camps.

3. Earthquake in Nepal (25 April 2015). *Cause:* Nepal lies where the Indian plate pushes under the Eurasian plate, building the Himalaya; accumulated stress was released suddenly. The epicentre was in the Gorkha district; the magnitude was about 7.8; a strong aftershock followed on 12 May 2015. *Effects:* nearly 9,000 deaths and many injured; hundreds of thousands of houses destroyed; historic monuments of the Kathmandu valley, including the Dharahara tower, collapsed; an avalanche struck Everest base camp; landslides blocked roads. India launched relief operations (Operation Maitri) and many countries sent help.

4. Oil spills in coastal areas of the United States. An oil spill is the release of crude oil or oil products into the sea or coastal waters from tankers, pipelines or offshore platforms.

  • *Deepwater Horizon (Gulf of Mexico, 2010):* on 20 April 2010 an explosion on an offshore rig operated for BP killed 11 workers; the damaged well leaked oil for 87 days before it was capped in July 2010. Oil reached the coasts of Louisiana, Mississippi, Alabama and Florida.
  • *Exxon Valdez (Alaska, 1989):* on 24 March 1989 the tanker ran aground in Prince William Sound and spilled a large quantity of crude oil, polluting a long stretch of remote coast.

5. Impact of oil spills on life and environment. Birds' feathers are coated, so they cannot fly or keep warm; fish, shellfish, dolphins and turtles are poisoned; coral and marshes are damaged. Coastal wetlands and beaches stay polluted for years; fishing and tourism lose income; clean-up workers and residents may be exposed to toxic chemicals. Clean-up uses booms, skimmers, controlled burning, dispersants (controversial) and beach washing. Prevention: double-hulled tankers and stricter drilling safety.

6. Comparing the cases. Floods are natural hazards worsened by human action (deforestation, embankments); the Nepal earthquake is a natural geological disaster whose losses were increased by weak buildings; oil spills are man-made disasters caused by accident or negligence.

Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills: key facts

Assam floods
  • Brahmaputra silt
  • Heavy monsoon
  • Majuli erosion
  • Kaziranga animals at risk
Bihar floods
  • Kosi: Sorrow of Bihar
  • Embankment breach 2008 at Kusaha
  • Millions affected
Nepal earthquake
  • 25 April 2015
  • Magnitude about 7.8
  • Gorkha epicentre
  • Nearly 9,000 deaths
  • Operation Maitri
US oil spills
Deepwater Horizon: 20 April 2010, 87 days | Exxon Valdez: 24 March 1989, Alaska

How to answer Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills questions

Begin each case study with the place and date.

  1. 1Write causes, then effects, then environmental impact in that order.
  2. 2Separate natural causes from human causes.
  3. 3Quote only the figures given: magnitude about 7.8, nearly 9,000 deaths, 11 workers, 87 days.
  4. 4End with a lesson, such as better planning, building codes or safety rules.

Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

The flooded school

Suppose a riverside school in a flood-prone district stands on stilts, keeps a boat and stock of dry rations, and holds a drill each June before the monsoon.

Link each measure to a stage of disaster management and a cause of flooding it addresses.

Try it first, then show the solutionSolution
  1. Stilts: mitigation, because they reduce damage when water rises.
  2. Boat and dry rations: preparedness for response.
  3. The drill before the monsoon prepares people to act when the river rises, which is likely because heavy monsoon rain and silt-laden rivers cause floods.

Answer: Stilts: mitigation; boat and rations: preparedness; drill: preparedness.

Memory hook: Stilt, store, drill.

Tricks to remember Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills

Short memory aids. Say each one aloud once, then use it on a question the same day.

  • SBM-K

    Silt, Braided river, Monsoon rain, Kaziranga: Assam flood clues.

    Use it when: Assam floods.

  • Plates push, Himalaya rises, quake strikes

    Indian plate under Eurasian plate: cause of the Nepal earthquake.

    Use it when: Nepal.

  • 20-11-87

    20 April 2010, 11 workers, 87 days: Deepwater Horizon numbers.

    Use it when: Oil spill.

Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Cause of the Nepal earthquake · 3 marks · Short answerBoard level

Explain the main cause of the 2015 earthquake in Nepal.

Try it first, then show the solutionSolution
  1. Nepal lies where the Indian plate pushes under the Eurasian plate.
  2. This collision builds the Himalaya and stores stress in the rocks.
  3. The stress was released suddenly, producing the earthquake (magnitude about 7.8, epicentre in Gorkha).

Answer: Sudden release of stress where the Indian plate pushes under the Eurasian plate.

Example 2: Kosi · 3 marks · Short answerBoard level

Why is the Kosi called the "Sorrow of Bihar"? State two causes of the 2008 floods.

Try it first, then show the solutionSolution
  1. It often floods and shifts its course, causing repeated suffering.
  2. In August 2008 it breached its embankment at Kusaha in Nepal and changed course.
  3. Causes: heavy rain, a high sediment load, flat land and embankment failure.

Answer: Because it floods and shifts course; causes include heavy rain, silt and embankment breach.

Example 3: Effects on Assam · 4 marks · Long answerHarder board level

Describe three effects of the Assam floods on life and the environment.

Try it first, then show the solutionSolution
  1. People are displaced and houses, crops and roads are destroyed.
  2. River-bank erosion eats away land, as on the island Majuli.
  3. Animals in Kaziranga drown or are hit by vehicles when they flee to higher ground; silt is deposited but waterlogging and erosion damage habitats.

Answer: Displacement and losses; erosion; danger to Kaziranga wildlife.

Example 4: Oil spill timeline · 4 marks · Long answerHarder board level

The Deepwater Horizon well leaked for 87 days after the explosion of 20 April 2010. (a) Why is this a man-made disaster? (b) How many workers died? (c) State two effects on marine life.

Try it first, then show the solutionSolution
  1. (a) It was caused by an accident on a drilling rig operated by a company, not by natural processes.
  2. (b) 11 workers.
  3. (c) Birds' feathers were coated and fish, shellfish, dolphins and turtles were poisoned; coral and marshes were damaged.

Answer: (a) Human accident (b) 11 (c) Coated birds, poisoned fish and other marine life.

Example 5: Compare disasters · 4 marks · Long answerHOTS / competency

Compare the Assam floods and the Exxon Valdez oil spill in terms of (a) type of disaster, (b) main cause and (c) a long-term impact on the environment.

Try it first, then show the solutionSolution
  1. (a) Floods: natural (made worse by human action); Exxon Valdez: man-made.
  2. (b) Floods: heavy monsoon rain, silt and breached embankments; Exxon Valdez: the tanker ran aground in Prince William Sound on 24 March 1989.
  3. (c) Floods: erosion and waterlogging damage land and habitats; oil spill: pollution of a long stretch of coast, harming wildlife and fisheries.

Answer: Natural against man-made; rain and silt against grounding; erosion against polluted coast.

Where students lose marks in Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills

The slips examiners see most often, and what to write instead.

  • Mistake: Mixing the dates of Nepal events

    Earthquake and aftershock dates are exchanged.

    Do this: Earthquake 25 April 2015; strong aftershock 12 May 2015.

    Usually costs: 1 mark.

  • Mistake: Calling the Kosi flood a purely natural event

    Human factors are ignored.

    Do this: Mention embankment breach and sediment load with the rain.

    Usually costs: 1 mark.

  • Mistake: Writing causes only

    The question asks for effects on life and environment.

    Do this: Use separate headings for causes, effects and environmental impacts.

    Usually costs: 2 marks.

  • Mistake: Inventing numbers

    Casualty or spill figures are guessed.

    Do this: Use only the figures given: about 7.8, nearly 9,000, 11 workers, 87 days.

    Usually costs: 1 to 2 marks.

Exam tips

  • Keep a three-line format for each case study: cause, effect, environment.
  • Mention the date and place in the first line.
  • Do not invent figures; say "millions" or "large areas" where only that is known.
  • Compare cases using natural, natural plus human and man-made as categories.

Practice questions on Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

  1. Q1 · 1 mark · MCQBoard level

    The Nepal earthquake of 2015 occurred on:
    (a) 25 April
    (b) 12 May
    (c) 24 March
    (d) 20 April

    Hint

    Aftershock was 12 May.

    Answer

    (a) 25 April 2015.

  2. Q2 · 1 mark · Very short answerBoard level

    Name the river island of Assam that is losing land to erosion.

    Hint

    In the Brahmaputra.

    Answer

    Majuli.

  3. Q3 · 1 mark · Very short answerBoard level

    What name was given to India's relief operation after the Nepal earthquake?

    Hint

    A friendly name.

    Answer

    Operation Maitri.

  4. Q4 · 2 marks · Short answerHarder board level

    Give two reasons why the Brahmaputra floods Assam frequently.

    Hint

    Silt and rain.

    Answer

    It carries a heavy sediment load that raises its bed and is wide and braided, and the monsoon brings very heavy rainfall; hill tributaries, deforestation and embankment breaches add to the floods.

  5. Q5 · 1 mark · Assertion-reasonHarder board level

    Assertion (A): The Exxon Valdez spill was a man-made disaster.
    Reason (R): The tanker ran aground and spilled crude oil into Prince William Sound.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

    Hint

    Cause of spill.

    Answer

    (a).

  6. Q6 · 4 marks · Long answerHarder board level

    Describe the effects of the Nepal earthquake on people, buildings and landscape.

    Hint

    Three headings.

    Answer

    People: nearly 9,000 died and many were injured. Buildings: hundreds of thousands of houses were destroyed and historic monuments in the Kathmandu valley, including the Dharahara tower, collapsed. Landscape: an avalanche struck Everest base camp and landslides blocked roads.

  7. Q7 · 5 marks · Case-basedHOTS / competency

    A coastal village depends on fishing and tourism. After an oil spill, the beach is covered with oil for months. Explain the effects on (a) livelihood, (b) wildlife and (c) health, and suggest two clean-up methods.

    Hint

    Think chain reaction.

    Answer

    (a) Fishing and tourism suffer heavy losses. (b) Birds, fish, shellfish and turtles are harmed and wetlands polluted. (c) Residents and clean-up workers may be exposed to toxic chemicals. Clean-up: floating booms and skimmers, controlled burning, beach washing (dispersants are controversial).

  8. Q8 · 3 marks · Short answerHOTS / competency

    "Human actions can turn a natural hazard into a bigger disaster." Support this using the Kosi floods of 2008 or the Assam floods.

    Hint

    Deforestation, embankments.

    Answer

    Deforestation in the catchment increases run-off and silt, and embankments that fail release water suddenly; settlements on the floodplain increase the people at risk. Thus rain alone does not cause the whole disaster.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

  1. 1.Which river is the Sorrow of Bihar?Show answer

    The Kosi.

  2. 2.Magnitude of the Nepal quake?Show answer

    About 7.8.

  3. 3.How many workers died on Deepwater Horizon?Show answer

    11.

  4. 4.Where did Exxon Valdez run aground?Show answer

    Prince William Sound, Alaska.

  5. 5.National park in Assam affected by floods?Show answer

    Kaziranga.

Case Studies: Assam-Bihar Floods, Nepal Earthquake and US Oil Spills: frequently asked questions

Why is Assam so flood-prone?

Monsoon rainfall, a silt-heavy braided Brahmaputra, hill tributaries, bank erosion, deforestation and embankment breaches.

Was the Nepal earthquake predicted?

The region lies in an active earthquake zone, but the exact time of an earthquake cannot be predicted.

How long did the Deepwater Horizon well leak?

87 days, until it was capped in July 2010.

What are dispersants?

Chemicals used to break up oil in water; they are controversial because they can themselves harm marine life.