GeographyCBSE Class 11 · Natural Hazards and Disasters

Tsunami, Cyclones, Floods, Droughts, Landslides and Disaster Management (Class 11 Geography, Chapter 6)

Updated 17 October 2026 · Fact-checked

A tsunami is a train of long waves from sudden sea-floor movement; tropical cyclones are intense lows between 30 degrees N and S that need warm moist air and Coriolis force; floods and droughts are the commonest hazards of the monsoon; landslides affect the Himalaya, Western Ghats and north-east. Disaster management works in three stages: pre-disaster, during disaster and post-disaster.

Understand Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India

Why this topic matters. Useful for the project and presentation by which CBSE assesses the chapter; conditions for cyclones, types of drought and management stages are the key concepts.

1. Tsunami. Earthquakes and volcanic eruptions suddenly move the sea floor and displace water as long waves. Over deep water a tsunami has a very long wavelength and small height; in shallow water the wavelength shortens while the period stays the same, so the height increases, sometimes to 15 m or more, hence 'shallow water waves'. They are frequent around the Pacific Ring of Fire. The 26 December 2004 tsunami killed over 200,000 people (about 230,000) around the Indian Ocean, and India then volunteered to join the International Tsunami Warning System.

2. Tropical cyclones. Intense lows between 30 degrees N and S, 500 to 1,000 km across and 12 to 14 km high, a heat engine powered by the latent heat of condensation. Conditions: (i) a large supply of warm, moist air; (ii) strong Coriolis force (none between 0 and 5 degrees); (iii) an unstable troposphere; (iv) absence of strong vertical wind shear. In India they arise over the Bay of Bengal and the Arabian Sea, mostly in October-November; coasts are hit hardest, with average velocities about 180 km/h and a storm surge.

3. Floods. Inundation when water spills over channels. Causes: runoff exceeding channel capacity, storm surge, long intense rain, melting snow, reduced infiltration; human causes include deforestation, unscientific farming and colonising floodplains. In India about 40 million ha are flood-prone (Rashtriya Barh Ayog), especially Assam, West Bengal and Bihar. Control: embankments, dams, afforestation, removing encroachments.

4. Droughts. Extended water shortage from inadequate rain, excessive evaporation and over-use. Types: meteorological (prolonged inadequate rainfall), agricultural (low soil moisture), hydrological (aquifers, lakes and reservoirs fall below what rain can replenish), ecological (ecosystem productivity fails). About 30 per cent of the area is drought-prone, affecting about 50 million people. Consequences: akal (food), trinkal (fodder), jalkal (water) scarcity; trikal is all three. Measures: water for people and cattle, then long-term aquifer identification, transfer of surplus water, drought-resistant crops and rainwater harvesting.

5. Landslides. Rapid sliding of large masses of bedrock, controlled by highly localised factors. Very high vulnerability: the young Himalaya, Andaman and Nicobar, the Western Ghats and Nilgiris and the north-east. Mitigation: restrict road and dam construction, limit farming to valleys and moderate slopes, afforest, build bunds and use terrace farming.

6. Disaster management. Pre-disaster (data, vulnerability zoning maps, awareness, preparedness), during disaster (rescue, evacuation, relief camps, food, water, medical aid) and post-disaster (rehabilitation, recovery and capacity-building). The Disaster Management Bill 2005 and the National Institute of Disaster Management are positive steps. Since natural disasters cannot be eliminated, mitigation and preparedness are the best options.

Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India: key facts

Cyclone conditions: Warm moist air
Strong Coriolis force (none at 0 to 5 degrees)
Unstable troposphere
No strong vertical wind shear; Latitude 30 degrees N to S.
Droughts: $M e t eor o l o g i c a l ∣ A g r i c u l t u r a l ∣ H y d r o l o g i c a l ∣ E co l o g i c a l$; Akal, trinkal, jalkal.
Floods in India: 40 million ha flood-prone | High: Assam, West Bengal, Bihar; Rashtriya Barh Ayog.
Management stages: $P r e - d i s a s t er : z o nin g, a w a r e n ess ∣ D u r in g : r esc u e, r e l i e f ∣ P os t : r e habi l i t a t i o n, c a p a c i t y - b u i l d in g$; Three stages.

How to answer Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India questions

Disaster case studies follow cause, impact and management.

1State the physical cause.
2Give two consequences with an Indian example.
3Give one immediate and one long-term measure.
4Link to the three stages of management.

Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India 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.

Warning before a cyclone

Suppose a coastal district gets a cyclone alert, moves people to shelters and stocks food and medicine in time.

Which stage of management is this?

Try it first, then show the solutionSolution

Preparedness and shelters are planned before the event.
Evacuation and shelters during the event.

Answer: Pre-disaster and during-disaster stages.

Memory hook: Prepare, then rescue.

Dry well year

Suppose a village has normal rain on paper but its wells and tanks are far below what rain can refill.

Which kind of drought is this?

Try it first, then show the solutionSolution

Water in aquifers and reservoirs is lower than what rain replenishes.
This is hydrological drought.

Answer: Hydrological drought.

Memory hook: Wells down, hydrological.

Tricks to remember Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India

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

Four needs for a cyclone
Warm moist air, Coriolis, unstable air, no shear
Use it when: Conditions.
MAHE
Meteorological, Agricultural, Hydrological, Ecological
Use it when: Droughts.
Pre, During, Post
Zoning, rescue, rehabilitation
Use it when: Management.

Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India: solved examples

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

Example 1: Storm surge · 1 mark · MCQBoard level

An abnormal rise of sea level during a cyclone is called:
(A) tsunami
(B) storm surge
(C) tidal bore
(D) neap tide

Try it first, then show the solutionSolution

The abnormal sea-level rise is the storm surge (1 mark).

Answer: (B)

Example 2: Types of drought · 2 marks · Very short answerBoard level

Name any two types of drought and define one. (2 marks)

Try it first, then show the solutionSolution

Two of meteorological, agricultural, hydrological, ecological (1 mark).
Definition of one, e.g. meteorological: prolonged inadequate rainfall (1 mark).

Answer: Meteorological and agricultural drought. Meteorological drought is a prolonged period of inadequate and mal-distributed rainfall; agricultural drought is low soil moisture causing crop failure.

Example 3: Cyclone conditions · 3 marks · Short answerHarder board level

State the conditions favourable for the origin of tropical cyclones. (3 marks)

Try it first, then show the solutionSolution

Large, continuous supply of warm, moist air and strong Coriolis force (1 mark).
Unstable troposphere creating local disturbances (1 mark).
Absence of strong vertical wind shear (1 mark).

Answer: A large and continuous supply of warm, moist air; a strong Coriolis force that prevents the centre from filling up (absent between 0 and 5 degrees); an unstable condition of the troposphere that creates local disturbances; and the absence of strong vertical wind shear.

Example 4: Assertion and reason: tsunami height · 1 mark · Assertion-reasonHarder board level

Assertion (A): A tsunami grows in height as it reaches shallow water.
Reason (R): In shallow water the wavelength shortens while the period stays the same.
(A) Both true, R explains A
(B) Both true, R does not explain A
(C) A true, R false
(D) A false, R true

Try it first, then show the solutionSolution

The chapter attributes the rise in height to shortening wavelength at constant period (1 mark).

Answer: (A)

Example 5: HOTS: flood-prone share · 5 marks · Long answerHOTS / competency

India has 328 million ha of area (3.28 million sq km) and about 40 million ha are flood-prone. Find the share of flood-prone land, and explain two human and two natural causes of floods and two control measures. (5 marks)

Try it first, then show the solutionSolution

3.28 million sq km = 328 million ha, since 1 sq km = 100 ha (1 mark).
Share = 40 / 328 x 100 = about 12.2 per cent (1 mark).
Natural: runoff beyond channel capacity, long intense rain, snow melt (1 mark).
Human: deforestation, colonising floodplains, disturbing natural drainage (1 mark).
Control: embankments, dams, afforestation, removing encroachments (1 mark).

Answer: Since 1 sq km = 100 ha, India has 328 million ha. The flood-prone share is 40 / 328 x 100 = about 12.2 per cent (a derived estimate). Natural causes include runoff exceeding channel capacity and long, intense rain or snow melt. Human causes include deforestation and colonising floodplains. Control measures include embankments and dams, afforestation and removal of encroachments on floodplains.

Where students lose marks in Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India

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

Mistake: Saying cyclones form at the equator
Warm sea assumed enough.
Wrong working
Cyclones form near 0 degrees.
Right working
Coriolis force is absent between 0 and 5 degrees, so they do not form there.
Do this: Mention Coriolis.
Usually costs: 1 mark.
Mistake: Confusing drought types
Names similar.
Wrong working
Hydrological drought is low soil moisture.
Right working
Hydrological: low water in aquifers, lakes and reservoirs; agricultural: low soil moisture.
Do this: Link each with its store.
Usually costs: 1 mark.
Mistake: Leaving out post-disaster stage
Only before and during.
Wrong working
Management has two stages.
Right working
Three: pre, during, post-disaster.
Do this: Add rehabilitation.
Usually costs: 1 mark.

Exam tips

Write a short cause-impact-management paragraph for each hazard.
Remember "trikal" as food, fodder and water scarcity together.
Link cyclones with storm surges for coastal management.

Practice questions on Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India

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

Q1 · 1 mark · MCQBoard level
A drought caused by prolonged inadequate rainfall is called:
(A) hydrological
(B) agricultural
(C) meteorological
(D) ecological
Hint
Rain.
Answer
(C)
Q2 · 2 marks · Very short answerBoard level
State the three stages of disaster management. (2 marks)
Hint
Before, during, after.
Answer
Pre-disaster, during disaster and post-disaster stages.
Q3 · 3 marks · Short answerHarder board level
Why do tropical cyclones lose force after moving inland? (3 marks)
Hint
Moisture, friction.
Answer
Tropical cyclones are heat engines powered by the latent heat of condensation of moisture from warm seas. Inland the supply of moisture is cut off, so the energy source weakens and the force decreases, which is why coasts suffer most.
Q4 · 3 marks · Short answerHarder board level
Describe the effects of floods and one benefit of silt. (3 marks)
Hint
Majuli.
Answer
Floods destroy crops, roads, rails, bridges and homes, wash away people and cattle and bring diseases such as cholera and hepatitis. A small benefit is fertile silt, for example good paddy on Majuli, the world's largest riverine island in the Brahmaputra.
Q5 · 4 marks · Short answerHOTS / competency
A hill state wants to reduce landslide losses while building roads and dams. Using the chapter, suggest four area-specific measures and name the highly vulnerable regions of India. (4 marks)
Hint
Restrict, afforest, terrace.
Answer
Restrict the construction of roads and dams, limit farming to valleys and moderate slopes, control large settlements in high-risk zones, and undertake afforestation, bunds and terrace farming. Highly vulnerable regions are the Himalaya, Andaman and Nicobar, the Western Ghats and Nilgiris and the north-east.

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.What is jalkal?Show answer
Water scarcity.
2.Which is the world's largest riverine island?Show answer
Majuli in the Brahmaputra.
3.How tall are cyclones?Show answer
12 to 14 km.
4.What kills many in a cyclone?Show answer
Storm surge and winds.

Tsunami, Tropical Cyclones, Floods, Droughts, Landslides and Disaster Management in India: frequently asked questions

When did the major tsunami strike?

26 December 2004.

Why can floods and droughts occur together?

Because of variability of the monsoon, different regions receive too much or too little.

Which Bill defined disaster in 2005?

The Disaster Management Bill, 2005.