In this guide
Fly over Bihar in the monsoon and you see a vast green plain threaded with shining rivers, many of them spreading into wide sheets of water. Almost all of Bihar is part of the middle Ganga plain — built over millions of years by sediment carried from the Himalaya. That single fact explains most of Bihar's geography: its fertility, its dense population, its floods and its scarcity of minerals.
Location and extent
| Feature | Detail |
|---|---|
| Area | About 94,000 sq km — around 2.9 per cent of India's area |
| Latitude | Roughly 24°N to 27°N |
| Longitude | Roughly 83°E to 88°E |
| Neighbours | Nepal (north), West Bengal (east), Jharkhand (south), Uttar Pradesh (west) |
| Landlocked | Yes — no coastline |
| Districts / divisions | 38 districts in 9 divisions |
Physical divisions
Bihar can be divided into four physiographic regions:
| Region | Location | Features |
|---|---|---|
| 1. Shivalik region | Extreme north-west — northern West Champaran | Himalayan foothills; forested |
| 2. North Ganga plain | North of the Ganga | Flat, low-lying; many rivers from the Himalaya; highly flood-prone |
| 3. South Ganga plain | South of the Ganga to the plateau edge | Slightly higher; rivers from the plateau; less flood-prone, more drought-prone |
| 4. Southern plateau fringe | Southern parts — Kaimur, Rohtas, Gaya, Nawada, Jamui, Banka | Edges of the Vindhyan and Chotanagpur plateaus; hills and uplands |
1. The Shivalik region
- A narrow strip in the north-west of West Champaran.
- Includes the Someshwar range and the Ramnagar Dun (a longitudinal valley) and the Harha valley.
- Contains Valmiki Tiger Reserve and the highest land in Bihar.
2. The north Ganga plain
- Built by rivers flowing from the Himalaya — the Ghaghara, Gandak, Burhi Gandak, Bagmati, Kamla, Kosi and Mahananda.
- Very flat, with a gentle slope towards the south-east.
- Rivers carry huge loads of sediment, build up their beds and frequently change course (the Kosi most dramatically).
- Many chaurs (depressions that hold water) and oxbow lakes (mauns).
- Among the most flood-prone regions in India.
3. The south Ganga plain
- Rivers flow north from the plateau — the Son, Punpun, Phalgu, Kiul, Sakri, Chandan and others.
- Rivers are seasonal; many dry up in summer.
- Includes the tal lands along the south bank of the Ganga — low-lying areas that are flooded in the monsoon and cultivated with pulses in winter (for example, the Mokama tal, often called the "pulse bowl" of Bihar).
- Historically the core of Magadha.
4. The southern plateau fringe
- The Kaimur plateau (Kaimur and Rohtas districts) — part of the Vindhyan system.
- The hills of Gaya, Nawada, Jamui and Banka, including the Rajgir hills and the Barabar hills — outliers of the Chotanagpur plateau.
- Contains most of Bihar's remaining minerals and forests after 2000.
Special landforms
| Landform | Meaning |
|---|---|
| Diara | Sandy riverine land between river channels and on river islands, cultivated after floods recede |
| Tal | Low-lying land along the Ganga's south bank, flooded seasonally, used for rabi pulses |
| Chaur | Saucer-shaped depressions in north Bihar that hold water for much of the year |
| Maun | Oxbow lakes left by shifting rivers |
Geology
- The plains are made of alluvium — older alluvium (bhangar) on higher ground and newer alluvium (khadar) near rivers.
- The south has older rocks of the Vindhyan and Chotanagpur systems.
- The north lies close to the Himalayan tectonic zone, which makes Bihar seismically active — the 1934 Bihar–Nepal earthquake was one of the most destructive in Indian history. Parts of north Bihar are in seismic zones IV and V.
How physiography shapes Bihar
| Physical feature | Consequence |
|---|---|
| Flat, fertile alluvial plain | High agricultural potential; very high population density |
| Himalayan rivers with heavy sediment | Floods; shifting courses; sand deposits |
| Plateau rivers in the south | Seasonal water; drought in parts |
| Few hard-rock areas after 2000 | Scarcity of minerals |
| Proximity to the Himalaya | Earthquake risk |
| Chaurs and tal lands | Wetlands; seasonal waterlogging; unique agriculture (makhana, pulses) |
Practice
Prelims-style:
- Which district of Bihar contains the Shivalik region?
- What is a chaur?
- What is the Mokama tal known for?
- Name two rivers of the south Ganga plain.
- Which states and country border Bihar?
Mains-style:
- "Bihar's physiography is both a blessing and a curse." Discuss.
- Explain how the physiography of north Bihar contributes to recurrent floods.
Map exercise
On a blank map of Bihar, mark the four physiographic regions, the Someshwar range, the Kaimur plateau, the Rajgir hills, the Mokama tal and the major rivers.
A note on dates and numbers. Exam patterns, vacancies and schedules change from year to year. Always confirm the current details in the latest notification on the Bihar Public Service Commission website .
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