GeographyISC Class 12 · Structure of India: Geological Formation, Relief and Drainage

Coastal Plains, Islands and River Systems of India (ISC Class 12 Geography)

Updated 17 October 2026 · Fact-checked

The Western Coastal Plain is narrow with estuaries and kayals; the Eastern is wider with large deltas. The Andaman and Nicobar Islands are larger, hilly and volcanic in part, while Lakshadweep is a group of 36 small coral islands. Himalayan rivers such as the Ganga and Brahmaputra are perennial with large basins and deltas; Peninsular rivers such as the Godavari and Narmada are seasonal and rain-fed.

Notice the western plain is squeezed between the Ghats and the sea, while the eastern plain is much wider and builds large deltas.

Illustration drawn for QuestionBuddy.

Understand Coastal Plains, Islands and River Systems of India

1. Western versus Eastern Coastal Plains.

Location: the western plain lies between the Western Ghats and the Arabian Sea; the eastern between the Eastern Ghats and the Bay of Bengal.
Width: western narrow; eastern wider.
Divisions: western has Kachchh and Kathiawar, Konkan, Kanara (Karnataka) and Malabar; eastern has Utkal (Odisha), the Northern Circars (Andhra Pradesh) and the Coromandel (Tamil Nadu).
Landforms: western rivers form estuaries and the Malabar coast is lined with lagoons called kayals; eastern rivers (Mahanadi, Godavari, Krishna, Kaveri) form large deltas, with lagoons such as Chilika and Pulicat.
Ports: the indented western coast has natural harbours; the eastern coast is smoother.

2. Islands. The Andaman and Nicobar Islands lie in the Bay of Bengal. They number several hundred, are larger and hilly, are the submerged extension of the Arakan Yoma mountains of Myanmar, carry dense forests, and include Barren Island with an active volcano. Lakshadweep lies in the Arabian Sea near the Kerala coast. It is a group of 36 small, low islands of coral origin, made of atolls and reefs.

3. Sources of the main rivers.

Ganga: the Gangotri glacier (as the Bhagirathi, at Gaumukh), joined by the Alaknanda at Devprayag.
Yamuna: the Yamunotri glacier.
Indus: near Lake Mansarovar in Tibet.
Sutlej: Rakas Tal near Mansarovar in Tibet.
Brahmaputra: the Chemayungdung glacier near Mansarovar (called the Tsangpo in Tibet).
Mahanadi: near Sihawa in Chhattisgarh.
Godavari: Trimbakeshwar, Nashik district, Maharashtra.
Krishna: near Mahabaleshwar, Maharashtra.
Kaveri: Talakaveri in the Brahmagiri hills, Kodagu, Karnataka.
Narmada: the Amarkantak plateau, Madhya Pradesh.
Tapi: Multai, Betul district, Madhya Pradesh.

4. Himalayan versus Peninsular rivers.

Source: glaciers and rain versus rain only.
Flow: perennial versus seasonal.
Length and basin: long with large basins versus shorter with smaller basins.
Valleys: deep gorges and V-shaped valleys (young) versus broad shallow valleys (old).
Courses: meandering in the plains with shifting beds versus fixed, straight courses.
Mouths: large deltas versus deltas for the east-flowing rivers and estuaries for the Narmada and Tapi.
Uses: irrigation and navigation in the plains versus hydel power from falls and rapids.

Coastal Plains, Islands and River Systems of India: key facts

Coastal plain divisions: West: Kachchh and Kathiawar
Konkan
Kanara
Malabar. East: Utkal
Northern Circars
Coromandel
Coastal landforms: West: estuaries and kayals | East: deltas, Chilika and Pulicat lagoons
Islands: Andaman and Nicobar: Bay of Bengal, hilly | Lakshadweep: Arabian Sea, 36 coral islands
Himalayan river sources: Ganga Gangotri
Yamuna Yamunotri
Indus, Sutlej, Brahmaputra near Mansarovar
Peninsular river sources: $M ahana d i : S iha w a ∣ G o d a v a r i : T r imbak es h w a r ∣ K r i s hna : M ahaba l es h w a r ∣ K a v er i : T a l ak a v er i ∣ N a r ma d a : A ma r k an t ak ∣ T a p i : M u l t ai$

Ganga	Gangotri
Yamuna	Yamunotri
Indus, Sutlej, Brahmaputra	near Mansarovar

How to answer Coastal Plains, Islands and River Systems of India questions

For comparison questions, list paired points under matching headings; for rivers, give source, state or region, and the sea they flow to only if asked.

1Write the two things being compared at the top of two columns.
2Use the same headings for each row (location, width, landforms, rivers).
3For river sources, name the exact place and its region, not just the state.
4For islands, state sea, size, origin and vegetation or rock type.
5Check that each pair of points contrasts rather than repeats.

Coastal Plains, Islands and River Systems of 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.

Planning a boat trip on a lagoon coast

Suppose a student plans to compare a houseboat trip on the backwaters of the Malabar coast with a boat trip on a large lagoon on the east coast.

Name the local term for the western lagoons and one eastern lagoon, and say which coast has the larger deltas feeding such lagoons.

Try it first, then show the solutionSolution

Lagoons on the Malabar coast are called kayals.
On the east coast lagoons include Chilika and Pulicat.
The east coast has the large deltas of the Mahanadi, Godavari, Krishna and Kaveri.

Answer: Kayals on the west; Chilika or Pulicat on the east; larger deltas on the east coast.

Memory hook: Kayals in Kerala; deltas on the east.

Choosing a river for a power station

Suppose an engineer must decide between a plains river of the Ganga type and a Peninsular river with a waterfall for a hydel plant, and also wants to know which one flows all year.

State which river flows all year and which offers falls and rapids suited to hydel power, with a reason for each.

Try it first, then show the solutionSolution

Himalayan rivers are perennial because glaciers and rain feed them.
Peninsular rivers are seasonal, but their courses have falls and rapids that suit hydel power.

Answer: Himalayan river: perennial; Peninsular river: falls and rapids for power.

Memory hook: Himalayan rivers never dry; Peninsular rivers fall.

Tricks to remember Coastal Plains, Islands and River Systems of India

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

West narrow, east wide
Western plain: narrow, estuaries, kayals. Eastern plain: wide, deltas, Chilika and Pulicat.
Use it when: Coastal plain comparison.
Three rivers from Mansarovar
Indus, Sutlej and Brahmaputra all rise near Lake Mansarovar in Tibet.
Use it when: River sources.
Two Madhya Pradesh sources
Narmada from Amarkantak, Tapi from Multai (Betul district).
Use it when: Peninsular river sources.

Coastal Plains, Islands and River Systems of India: solved examples

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

Example 1: Sources of two rivers · 2 marks · Short answerBoard level

Name the sources of the Godavari and the Kaveri.

Try it first, then show the solutionSolution

Godavari: Trimbakeshwar in Nashik district, Maharashtra.
Kaveri: Talakaveri in the Brahmagiri hills, Kodagu, Karnataka.

Answer: Godavari: Trimbakeshwar. Kaveri: Talakaveri.

Example 2: Lakshadweep · 2 marks · Short answerBoard level

Describe the Lakshadweep islands in two points.

Try it first, then show the solutionSolution

They are 36 small, low islands in the Arabian Sea near the Kerala coast.
They are of coral origin, made of atolls and reefs.

Answer: 36 small coral islands (atolls and reefs) off the Kerala coast in the Arabian Sea.

Example 3: Andaman and Nicobar versus Lakshadweep · 3 marks · Short answerHarder board level

Identify the island group from each clue and say which of the two groups has the larger and hillier islands: (a) atolls and reefs near the Kerala coast, (b) an active volcano on Barren Island, (c) a submerged extension of the Arakan Yoma, (d) 36 small low islands.

Try it first, then show the solutionSolution

(a) and (d) point to Lakshadweep, in the Arabian Sea.
(b) and (c) point to the Andaman and Nicobar Islands, in the Bay of Bengal.
The Andaman and Nicobar group has the larger, hillier, forested islands; Lakshadweep consists of small, low coral islands.

Answer: (a), (d) Lakshadweep; (b), (c) Andaman and Nicobar; the Andaman and Nicobar Islands are larger and hillier.

Example 4: Himalayan and Peninsular rivers · 4 marks · Long answerHarder board level

Give four differences between Himalayan rivers and Peninsular rivers.

Try it first, then show the solutionSolution

Source and flow: Himalayan rivers are fed by glaciers and rain and are perennial; Peninsular rivers are rain-fed and seasonal.
Valleys: gorges and V-shaped valleys versus broad, shallow valleys.
Courses: shifting, meandering in the plains versus fixed, straight courses.
Mouths and use: large deltas and irrigation/navigation versus estuaries (Narmada, Tapi) or deltas, with hydel power from falls.

Answer: Himalayan rivers are perennial, long, gorge-cutting and delta-forming; Peninsular rivers are seasonal, shorter, in broad old valleys and have fixed courses.

Example 5: Why estuaries on one coast and deltas on the other · 4 marks · Long answerHOTS / competency

The Narmada and Tapi flow into the Arabian Sea, but the Mahanadi and Godavari flow into the Bay of Bengal. (a) Name the landform at the mouth of each pair. (b) Using the width of the two coastal plains, say what the chapter page suggests as a reason. (c) Name one lagoon on each coast.

Try it first, then show the solutionSolution

(a) Estuaries for the Narmada and Tapi; deltas for the Mahanadi and Godavari.
(b) The western plain is narrow while the eastern is wide, which gives eastern rivers room to spread their deposits; the page states the contrast in width and landforms, and the link is the reasoning offered here.
(c) West: a kayal of the Malabar coast; east: Chilika or Pulicat.

Answer: (a) Estuaries (west), deltas (east) (b) narrow versus wide plains (c) kayals in the west; Chilika or Pulicat in the east.

Where students lose marks in Coastal Plains, Islands and River Systems of India

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

Mistake: Giving a state instead of the exact source
Candidates write Maharashtra for the Godavari without the place.
Wrong working
Godavari rises in Maharashtra.
Right working
Godavari rises at Trimbakeshwar, Nashik district, Maharashtra.
Do this: Learn the place and state together.
Usually costs: 1 mark.
Mistake: Swapping Narmada and Tapi sources
Both are in Madhya Pradesh.
Do this: Narmada: Amarkantak; Tapi: Multai.
Usually costs: 1 mark.
Mistake: Writing that Lakshadweep is volcanic
Barren Island, with an active volcano, belongs to the Andaman group.
Do this: Lakshadweep is coral (atolls and reefs).
Usually costs: 1 mark.
Mistake: Comparison without paired headings
The two coasts or river types are described separately.
Do this: Match each point: location with location, width with width.
Usually costs: 1 to 2 marks.

Exam tips

Learn each source as place plus state, as the syllabus asks for eleven rivers.
Use one marking point per mark in comparisons.
Spell kayals, Chilika and Pulicat correctly.
Mention that Himalayan rivers are perennial; the contrast with seasonal rivers earns a mark every time.

Practice questions on Coastal Plains, Islands and River Systems of 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
The Tsangpo is the name used in Tibet for the:
(a) Indus
(b) Sutlej
(c) Brahmaputra
(d) Ganga
Hint
Chemayungdung glacier.
Answer
(c) Brahmaputra.
Q2 · 3 marks · Short answerHarder board level
Write the divisions of the Eastern Coastal Plain and name the state each lies in.
Hint
North to south.
Answer
Utkal (Odisha), Northern Circars (Andhra Pradesh) and Coromandel (Tamil Nadu).
Q3 · 2 marks · Short answerHarder board level
Name the river that forms the Ganga at Devprayag along with the Bhagirathi, and state the glacier source of the Bhagirathi.
Hint
Gaumukh.
Answer
The Alaknanda; the Bhagirathi rises at Gaumukh in the Gangotri glacier.
Q4 · 4 marks · Long answerHarder board level
A shipping company wants natural harbours and also wants to know where river deltas are found. (a) Which coast has the indented shoreline with natural harbours? (b) Which coast has the large deltas? (c) Name the divisions of that delta coast and one lagoon on it.
Hint
Indented west, smooth east.
Answer
(a) The western coast. (b) The eastern coast, with the deltas of the Mahanadi, Godavari, Krishna and Kaveri. (c) Utkal, Northern Circars and Coromandel; Chilika or Pulicat.
Q5 · 4 marks · Long answerHOTS / competency
A map shows a river that starts from a glacier, cuts a deep gorge in the mountains, meanders in the plains and ends in a large delta. Another river has a straight course in a broad shallow valley and ends in an estuary. (a) Classify each. (b) Name one river of each type that ends as described. (c) Which type is likely to dry up in summer?
Hint
Glacier-fed versus rain-fed.
Answer
(a) The first is a Himalayan river, the second a Peninsular river. (b) Brahmaputra or Ganga; Narmada or Tapi. (c) The Peninsular type, which is seasonal and rain-fed.

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.Source of the Krishna?Show answer
Near Mahabaleshwar, Maharashtra.
2.Source of the Yamuna?Show answer
The Yamunotri glacier.
3.How many islands form Lakshadweep as per the chapter page?Show answer
36 small coral islands.
4.Name the coastal division of Tamil Nadu on the east coast.Show answer
The Coromandel.
5.Which islands carry an active volcano on Barren Island?Show answer
The Andaman and Nicobar Islands.

Coastal Plains, Islands and River Systems of India: frequently asked questions

What are kayals?

Lagoons lining the Malabar coast.

Which rivers rise near Lake Mansarovar?

The Indus, the Sutlej and the Brahmaputra.

Do Peninsular rivers have estuaries?

The Narmada and Tapi have estuaries; the east-flowing rivers form deltas.

Which islands are the extension of the Arakan Yoma?

The Andaman and Nicobar Islands.