Geographical Structure of Bihar | BPSC Preparation: All subjects - BPSC (Bihar) PDF Download

Bihar is situated in the Eastern part of India. It has geographical area of 94,163 sq km which makes it the 12th largest state of India and covers 2.86% of the total geographical area of the country.

Geographical Location of Bihar

• The geographical location of Bihar ranges from 24°21'10" N to 27°31'15" N in latitude and from 83°19'50" E to 88°17'40" E in longitude. 
•  Bihar's latitudinal range is 3° and its longitudinal range is 5°. 
•  It is entirely located in the Northern Hemisphere and lies north of the Tropic of Cancer. 
•  Bihar is a land-locked state, bordered by Nepal to the north, Uttar Pradesh to the west, Jharkhand to the south, and West Bengal to the east. 
•  The shape of Bihar is rectangular. 
•  Its width from west to east is 483 km and its length from north to south is 345 km. 
•  The average elevation of Bihar is 53 meters (173 feet) above sea level. 
•  It is linked by National Waterways No-1, which runs from Allahabad to Haldia. 
•  Bihar is located 200 km away from the nearest coastline.

Boundaries of Bihar

International Boundary

Bihar has 729 km international boundary with Nepal. Around 7 districts share their boundaries with Nepal such as West Champaran, East Champaran, Sitamarhi, Madhubani, Supaul, Araria and Kishanganj.

State Boundaries

The district boundaries of Bihar with other states are as follows:

• Districts having Boundary with West Bengal Three districts share their boundary with West Bengal, which is located to the East of Bihar. These are Kishanganj, Purnia and Katihar district.
• Districts having Boundary with Jharkhand Seven districts share their boundary with Jharkhand state, which is located in Southern Bihar. These are Bhagalpur, Banka, Nawada, Jamui, Gaya, Aurangabad and Rohtas districts. 
• Districts having Boundary with Uttar Pradesh Eight districts share their boundary with Uttar Pradesh which is located in Western part of Bihar. These are Rohtas, Kaimur, Buxar, Bhojpur, Saran, Siwan, Gopalganj and West Champaran districts. 
• Other Districts There are 15 districts in Bihar which do not share their boundary with any state or country. These districts are Darbhanga, Samastipur, Vaishali, Sheohar, Khagaria, Saharsa, Madhepura, Begusarai, Munger, Lakhisarai, Sheikhpura, Nalanda, Jahanabad, Arwal and Patna.

Geological Structure of Bihar

• The Geology of Bihar includes both old and new types of rocks.
• The North-Western hills were created during the Tertiary period.
• Bihar's plain, which is the youngest in terms of geological time, was formed by river deposits from the Himalayas.
• This plain came into existence as rivers flowing rapidly from the southern slopes of the newly lifted Himalayas filled a large trough with heavy materials.
• The geology of Bihar consists of rocks from the Pre-Cambrian period up to the Quaternary rocks of the Pleistocene period.
• The northern region of Bihar is associated with the Quaternary rock period.
• North Champaran is linked to the Tertiary rock period.
• Rohtas and Aurangabad are connected to the Vindhyan rock period.

 The rocks found in Bihar on the basis of structure can be classified into four types:

The Dharwar Rocks

• Dharwar rocks are one of the youngest rocks. These rocks are of Pre-Cambrian age in which rocks were formed as metamorphosed which are coarse, medium and fine textured. 
• Archaean sediments, quartzite, phyllite, gneiss, schist and slate are rocks of Dharwar group. These rocks are found in South-Eastern part of Bihar like Munger, Jamui, Nawada, Gaya, Nalanda and Nawada districts. In this part, Dharwar rocks are dominated by mica-schist.
• The hills found in these regions are part of Chota Nagpur plateau. 
• There rocks are equivalent in age with Archaean rocks.

The Vindhyan Rock

• These rocks were formed during the Pre-Cambrian period.
• They are rich in limestone and pyrite, which is used to produce sulphur for the cement industry.
• In the Son river valley, you can find alluvial deposits over the Vindhyan rocks.
• The Vindhyan rock group is divided into two sections: the Lower Vindhyan group and the Upper Vindhyan group.
• These rocks have been utilized in building notable structures such as:
  • Maner Dargah
  • Sasaram
  • Agra
  • Delhi
  • Jaipur
  • Sarnath
  • Sanchi
• Other Buddhist Stupas
• Evidence of volcanic structures has been discovered in Nabinagar, located in the Aurangabad district.
• These rocks consist of horizontally bedded sedimentary rocks such as sandstone, quartzite, limestone, dolomite, and shale.
• A significant portion of this system is represented by the Kaimur series.
• The Vindhyan rocks are valuable for construction purposes.
• They act as a dividing line between the Ganga plain and the Deccan.
• These rocks are primarily located in the South-Western part of Bihar, between the Kaimur district and the Son river valley in the Rohtas district.

The Tertiary Rocks

• The Himalayas were created during the tertiary period.
• They formed from the uplift of sediments that were deposited in the Tethys Sea between the Eurasian plate and the Indian plate.
• The tertiary rocks can be found in the Himalayan Terai region of Bihar and in the Shiwalik hills.
• These rocks were formed during the Mesozoic era, specifically in the Miocene and Paleocene eras.
• Examples of these tertiary rocks include sandstone, boulder clay, and conglomerate.
• These rocks contain deposits of petroleum and natural gas because they were formed from the sediments of the Tethys Sea.
• Notable locations where these rocks are found include Ramnagar Doon and the Someshwar hills, which are in the northwestern part of West Champaran district.

The Quaternary Rocks

• These formations occurred during the Pleistocene and recent periods.
• During the Pleistocene and recent times, the uplift of the Shiwalik hills led to the deposition of alluvium in the downwarped area between the Himalayas and the Chota Nagpur plateau, as well as in the Indus-Ganga trough.
• During this time, the country took on its current shape, and the plants and animals we see today began to establish.
• The rocks found in this region include sandstones, alluvium, conglomerate, and coarse gravels.
• A large, gently sloping area known as the Bihar plain was formed by the sediments deposited by rivers.
• In the Ganga plain region, these rocks are categorized as sedimentary rocks.
• The depth of alluvium in the Bihar plain reaches about 6000 meters.
• The deepest alluvium is located in the areas surrounding the Patna district.
• There are two types of alluvium present:
  • Bhangar: This is the older alluvium, which consists of coarse grains, sands, and calcium carbonate. It is found in higher areas and is less likely to be affected by floods.
  • Khadar: The newer alluvium, known as Khadar, is made up of sand, silt, and clay. It is located in lower areas and is often subject to flooding.

Physiographical Division of Bihar

The physiographic structure of a place largely depends on the climate, soil, vegetation and land use of that particular region. The regional study of Bihar also depends on its varied relief, natural features, soils land and vegetation. On the basis of physical and structural conditions, Bihar can be divided into three physiographic units. Physiographic division of Bihar is shown below:

1. Shiwalik Range or Himalayan Mountainous Ranges

• Ramnagar Doon
• Someshwar Range
• Harha Valley

2. Bihar (Indo-Gangetic) Plain

Northern Bihar Plain

• Division on the basis of Regional Variation:
  • Mahananda Plain
  • Kosi Plain
  • Kamala Plain
  • Bagmati Plain
  • Gandak Plain
  • Ghaghara Plain

South Gangetic Plain

• Division on the basis of Regional Variation:
  • Chandan Plain
  • Kiul Plain
  • Tal Region
  • Central South Bihar Plain
  • Shahabad Plain

3. Southern Narrow Plateau

• Kaimur/Rohtas Plateau
• Gaya Hilly Region
• Nawada Hilly Region
• Rajgir Hilly Region
• Munger Hilly Region

Shiwalik Range

This region is a part of the Himalayan mountains and it comprises an area of about 932 sq km. It is located in the North-Western part of Bihar in the Northern region of West Champaran district over an area 32 km long and 6-8 km wide. Its average height is about 80-250 m. It was formed in the Cenozoic era. This region is sub-divided into three parts based on local variation. These are as follows:

i. Ramnagar Doon 

• This broken hilly range lies on the Southern side of the Someshwar hills. 
• This Southern range is 32 km long and 6-8 km wide. Highest peak of this range is near Santpur (242 m). 
• Harha river valley lies in the North-East of Ramnagar Doon. 
• Ramnagar Doon is a range of many smaller hills which is spread over 214 sq km area. It can be seen in the form of Southern range. 

ii. Someshwar Range 

• This range was formed in the Tertiary period. These hills are located in the North Gangetic plain and surrounded the North-Western part of Bihar.
• It is 70 km long and covers an area of 84 sq km. Its average height is more than 450 m. 
• It is Northern range which spreads from the point where Triveni canal begins and ends near Bhikhna Thori pass. 
• Highest peak of the state, Someshwar fort (880 m) is situated in this range. 
• There are many passes formed by river action such as Someshwar, Bhikhna Thori and Marwat passes formed by Turipani, Kudi and Harha rivers, respectively. 
• This range forms the international boundary between Nepal and India. 

iii. Harha Valley 

• This valley lies between Someshwar and Ramnagar ranges. It is 21 km long and 152 m in height. It spreads over an area of 214 sq km. The maximum height of this valley is about 240 m. It is higher than the alluvial plain of the Ganga plain. 
• It is also known as ‘Doon Valley’

The Bihar (Indo-Gangetic) Plain

• The plain stretches between the Northern mountains and the Southern plateau region, extending from Nepal to the Chota Nagpur plateau. 
•  It is formed by the Ganga River and its tributaries, covering about 96.7% of the total area of the state. 
• The plain is bounded by the 150 m contour line in both the North and the South.
• The Bihar plain covers an area of 90,650 sq km.
• This area is partly the bed of the Tethys Sea, where rivers from the Himalayas and the Chota Nagpur plateau have deposited sediment.
• The topography in the North is generally flat, while in the South, there are hills like Gaya, Rajgir, and Kharagpur.
• The slope of the plain runs from West to East.
• The plain is wider in the Western part compared to the Eastern part.
• The average slope is about 5-6 cm per km.
•  The average height of the plain ranges from 75 m to 120 m, while the average depth is between 1000 m to 1500 m. 
•  The Ganga River divides the plain into two sections: the Northern Bihar plains and the Southern Bihar plains.

These are discussed below:

The Northern Bihar Plain/North Gangetic Plain 

• It is located to the North of the Ganga river. It has an area of about 56 980 sq km. It covers the area of Tirhut, Saran, Purnia, Darbhanga and Koshi divisions. extends from Ghaghara-Gandak doab in West to Mahananda valley in the East. 
• This plain is formed by alluvial deposits by the rivers like Gandak, Ghaghara, Burhi Gandak, Bagmati, Kamla, Kosi and Mahananda. 
• The North-Western part of Northern Bihar plain in East and West Champaran district is known as Terai area with high elevation. The soil of this region is rocky and porous with higher percolation level resulting in higher water level. The Terai region has sal forests and tall reed grass. South of the Terai is marshy land. 
• The slope of this plain is from North to South and from North-West to South-East. 
• This region is a flood prone area. About 76% area of this plain is flood potential area.
• The Northern part of this plain is comparatively higher. It is a place of alluvial fans which have been formed by the sediments of Gandak, Burhi Gandak, Kosi and Mahananda rivers. These rivers are famous for changing their courses. Kosi is known as ‘The Sorrow of Bihar’. 
• Important feature of this region is Chuars which are basically oxbow lakes or abandoned channels of the rivers. These are found in Begusarai, Samastipur, Saharsa and Katihar districts. 
• This Northern Bihar plain is divided into Doabs such as Ghaghara- Gandak Doab, Gandak-Kosi Doab, and Kosi-Mahananda Doab. Doab is a land lying between two converging rivers. 
• Diara (a land created by deposition of sand and alluvial soils over the decades) is also an important feature in this plain.

Division of Northern Bihar Plain

The North Bihar plain is divided on the basis of drainage system and on the basis of regional variations. The division of Northern Bihar Plain is discussed below:

On the Basis of Drainage System Mahananda Plain

• It is located to the Easternmost part of the North Bihar in the North, West Bengal in the East, the Ganga river in the South and Kosi river in the West. 
• The Mahananda river played a great role in forming this plain, especially the upper surface having marshy land, levee land, older alluvium, etc.
• Kosi and Mahananda rivers carry heavy loads of sand and gravel (kankar) and deposits on their beds and flood plains, raising some areas relatively higher and creating low-lying areas where such deposition occurs in smaller quantity.
• The slope of this plain is from North to South. It covers about one-tenth area of the North Bihar plain.

Kosi Plain 

• This plain is surrounded by Nepal border in the North, Mahananda plain in the East, Ganga river in the South and Kamla river in the West. 
• It covers Supaul, Saharsa, Madhubani, Darbhanga and Madhepura districts of Bihar. The slope of this plain is from North to South. It covers approximately one-sixth area of the North Bihar plains. 
• The Kosi river is known to change its course and has also shifted from East to West. Thus, this plain also got shifted Westward. Due to its shifting nature, it is the most flood affected area of the state. 

Kamala Plain 

• This plain is located in the central part of the North Bihar plains. This plain is surrounded by Indo-Nepal border in the North, Kosi plain in the East, Ganga river in the South and Bagmati plain in the West. The slope of this plain is from North-West to South-East. 
• Kamala river is also known to change its course, thus due to this action of the river a large number of chaurs have been formed in this region.

Bagmati Plain

• This plain is located between Gandak plain in the West and Kamala plain in the East. The plain covers Sitamarhi, East Champaran, Muzaffarpur, Samastipur and Sheohar districts of Bihar. This region has a number of Chaurs. 
• Important tributaries of Bagmati river are Lal Bakaiya, the Lakhandei and the Adhwara. 
• This plain also has a number of marshy lands which have formed by abandoned river courses, meanders and unequal deposition of sand and loam.
• The plain has gentle slope which goes from North-West to South-East.

Gandak Plain

• This plain lies between Ghaghara plain and the Bagmati plain. The Gandak river enters in the North-Bihar plain near Valmiki Nagar in West Champaran and meets the Ganga river near Hajipur. 
• In the North, the plain has a slope from North to South and in the South, it has a slope to South-Eastwards. 
• Due to shifting course of rivers, the plain has a vast low lying tract which appears like long semi-circular Chair. 

Ghaggar Plain 

• This is the Western most part of the North Bihar plain. It covers Siwan, Gopalganj and Saran districts of Bihar. 
• It is considered a part of the Ghaghra-Gandak interfluvial region, which is known as ‘Ghaghra-Gandak Doab’. It is also known as ‘Sarvan plain’.
• Important features of this plain are Diara land within the river, Chaur or vast low-lying areas and higher levees. This river is also known for the number and variety of changes. 
• During rainy season, the vast expanses of lowland, along the river channels, are flooded but are shown later during the dry season. Manjhi, Ekma, Giaspur and Barauli are known for their important Chaurs in this plain.

Distribution on the Basis of Regional Variation 

On the basis of regional variation, the North Gangetic plain can be divided into four divisions, such as:

Bhabar Region 

• Bhabar is a region of South of the lower Himalayas and Shiwalik hills. 
• This is located in the Northern part of Bihar in the form of a narrow belt of about 10 km wide from West to East. This region has a deposition of sand and gravels. 
• This region is extended in 7 districts such as East Champaran, West Champaran, Sitamarhi, Supaul, Madhubani, Kishanganj and Araria.

Bangar Region 

• This region has deposits of old alluvial soil. This region is free from frequent floods. It is located in the North-Western part of Bihar.

Khadar Region 

• This region has deposits of newer alluvium. Newer alluvium is deposited every year through the sediments and silt brought by the flood water.
• This region is extended in the North and North-Eastern plain from Gandak in the West to Kosi in the East.

Chaur (Man) 

• Chaurs are low-lying regions and oxbow-lakes which are formed by rivers and excessive rain in the North Gangetic plains. 
• Important Chaurs are Lakhani Chaur (West Champaran), Sundarpur Chaur (East Champaran), Tetariya Chaur, (West Champaran), Madhopur Man, Saraiya Man, etc. These are important source of fresh and deep water. 
• Rajmahal hills and Kaimur plateau demarcate its boundary in the North-East and North-West, respectively which lies from South of Ganga river to the North of Chota- Nagpur plateau. These hills are located in Jehanabad, Nalanda and Munger districts of Bihar.

South Bihar Plain/South Gangetic Plain

• It is smaller in area than North Bihar plain. It lies from South of Ganga river to the North of Chota Nagpur plateau. 
• Raj Mahal hill and Kaimur plateau demarcate its boundary in the North-East and North-West, respectively. It is triangular in shape with wider West and narrower East part. 
• Many hills are located in the South Bihar plain such as hills of Gaya (266 m), Rajgir (466 m), Barabar, Giriak, Sheikhpura, Jamalpur and Kharagpur (510 m) hills.
• These hills are located in Jahanabad, Nalanda and Munger districts of Bihar. These hills are the outliers of Chota Nagpur plateau and termed as residual hills. 
• This plain has been built of the alluvium brought by Karmanasa, Son, Punpun, Paimur, Phalgu, Kiul, Harohar, Man river and their feeders from the Southern hilly areas. 
• Unlike the North Bihar plain, the South Bihar plain is higher in the South and slopes towards the Ganga, but its slope is not as gradual as of the North Bihar plain. 
• The South Bihar plain is stable and not prone to floods except in limited areas as compared to North Bihar plain which is prone to floods. 

Chandan Plain

• This plain forms the Eastern most part of the South Bihar plain. This covers Banka and Bhagalpur districts of Bihar. 
• This plain has been formed by Chandan river which originates from the Digaria hills, a part of Rajmahal hills and its tributaries. 
• This plain is surrounded by plain of the Ganga river in the North, Godda in the East, Deoghar in the South and Jammu in the West. 
• The Northern part of this plain is homogeneous and has fertile soils while its Southern part is relatively undulating and wooded. 
• The plain covers about one-tenth area of the South Bihar plain and it slopes from South to North.
• The areas of Mandar hill in Banka, Katoria, Belhar and Bhitia have rough terrain while Rajaun, Amarpur and Shambhuganj, etc are homogeneous in nature having loam soils.

Kiul Plain 

• This plain is located in the West of Chandan plain, East of Mokama Tal region and North of Chakai plateau. The plain covers areas of Jhajha, Sikandra, Lakshmipur, Patsanda and Majhwa development blocks. 
• The Southern part of this plain is rolling in nature which covers areas of the development blocks of Chakai, Simutala, Godai, Bishunpur, etc. 
• The Northern parts of this plain have fertile soil while the Southern parts have coarse soils. 
• The fertile alluvial soil plain of the Ganga river lies in the North of this Kiul region. In the South of this alluvial belt, the Kharagpur hills form a watershed between Kiul river (drains West region) and Man river (drains East region). The slope of this plain is from South to North. 

Tal Region 

• This is a saucer shaped low lying area which gets filled with water during monsoon season and looks like a large lake. 
• It lies South of the higher levee of Ganga river, west of Kiul plain which has relatively higher land and east of Central South Bihar plain. It is 25 km wide and located from Patna to Mokama.
• Mokama Tal is extended from Fatuha to Lakhisarai. It is also known as Sickness of Bihar. 
• Around 1,06,200 hectare land of this region is low lying which gets filled by rain water during monsoon. 
• This plain has been built by alluvium brought by rivers from the Southern hills. This is a fine quality alluvium. 
• The rivers Punpun, Paimar and Phalgu does join the Ganga river straightly due to higher Southern levee of Ganga river. 
• Thus, these rivers before reaching levee turn towards east and flow parallel to Ganga river for some distance. Thus, a vast water body is created in this region. 
• At some distance, some rivers form distributaries and become extinct in Tal region. For example, Phalgu river which extinct here and its sand makes the land unfertile.

Central South Bihar Plain

• It is a triangular shaped plain and it is also known as Magadh. It is surrounded by Ganga river in the North, Tal region in the East, the Southern hilly terrain in the South and Son river in the West. 
• Although, there is absence of any significant boundary in the South, however, the Southern hilly terrain forms its Southern boundary. 
• It has an area of about 1,230 sq km and covers districts of Gaya, Jehanabad, Aurangabad, Patna, Nalanda and Nawada.
• This plain has been formed by the Ganga river, its main tributaries like, Punpun, Son and distributaries of Phalgu river. 
• The slope of this plain is from South-West to North-East. 
• This plain is divided into four sub-divisions such as the flood plain of the Ganga, elongated adjoining low lying area parallel to the Ganga levee, plain land of older alluvium and rising plain with slight swells bordering plateau fringe. 

The Shahabad Plain 

• This is an extensive low lying plains. It is located to the Western most part of the South Bihar plain. 
• It is surrounded by Ganga river in the North, Son river in the East, Kaimur plateau in the South and Karmanasa river in the West. 
• It covers Bhojpur, Buxar and some parts of Kaimur districts. It has been formed by the Ganga river and its tributaries such as Karamnasa and Son. 
• The plain is divided into two sub-divisions such as: 
  • The first part lies between the Ganga river and the main line of Eastern railway. The low lying land along the Ganga river is a flood prone region which is well fertilised by the silt and has fertile soil. 
  • The second large tract of land lies South of the railways to the foot of the Kaimur plateau. It comprises an area about 5.7 thousand sq km. It is also a flat alluvial plain.

The Southern Narrow Plateau

• The hilly and plateau region lies in the extreme South of the South Bihar plain (Southern part of Bihar). It is the frontier of Chota Nagpur plateau. 
• It is a narrow belt which extends from Kaimur district in the West to Munger and Banka districts in the East. 
• It is an undulating tract of land which is full of hills and extending from Kaimur plateau in the West to the hilly areas of the Banka in the ast. 
• This region consists of hard rocks like gneiss, schist and granite. 
• It is one of the oldest parts of Bihar. It is the extended part of the Peninsular plateau of India, which is spread in Kaimur, Rohtas, Nawada and Munger districts. 
• As it is the part of Peninsular plateau, it is formed by hard and ancient rocks.

Kaimur/Rohtas Plateau 

• It has an area of about 1200 sq km which covers most areas of Kaimur district. 
• It is 80 km wide. Its average height ranges from 300 m to 450 m. 
• It extends along the Southern boundary of Kaimur district in the South to Shahabad plain in the North. 
• Rohtasgarh is the highest point of this region with an elevation of 495 m above sea level. 
• The region is mostly comprised of Vindhyan rocks and thus is a part of Vindhyan range.
• The region has several hills which have deep gorges formed by the hill streams. It is the oldest physiographic region of Bihar.

Gaya Hilly Region

• This broken undulating part lies in the Southern part of the Gaya, Aurangabad and Nawada districts. This region merges into long ranges of hills and a wide belt of brush wood jungle lies at its base. 
• This part is high, barren and is not fit for much cultivation. Gidhour hills lie across the Southern boundary of Gaya and Nawada and are composed of Dharwars. They are highly metamorphosed and have mica. 
• The older rocks of this region are mostly foliated (consisting of thin sheets) gneiss and have a great variety of crystalline rocks. There lie isolated hills in the form of outcrops of Chota Nagpur plateau surrounded by alluvial plains. 
• Ganjas Bhindas and Jethian are located in this region which are long low outlying ranges. They extend from Bodh Gaya North-Eastward and rise at the Hadiya hill to a height of 441 m. 
• A ‘king of hills’ lies in Gaya town as Ramshila hills (214 m) on the North, Katari hills (136 m) on the West, Brahamyani hill (238 m) on the South and Pretshila hill (262 m) on the North-West. 
• Other important hills in the region are Maher hill (482 m) highest point of this region, Prahara hill (358 m), Bayari Pahar (408 m), Tari Pahar (357 m), Satgharwa Pahar (343 m), Loharawa Pahar (334 m), Barabar hill (307 m), Murgara Pahar (305 m), Harha Pahar (300 m), Songa Pahar (300 m), Gidh Pahar (281 m), Dwar Pahar (275 m), Ranidih Pahar (269 m), etc. 
• Barabar and Nagarjuna hills are located on the border of Gaya and Jehanabad.

Nawada Hilly Region

• This region stretches from the Ganga River in the north to the southern part of Nawada district.
• Spurs in the form of hills and ranges extend from the Chota Nagpur Plateau, separated by smaller valleys, with some reaching elevations of about 360 m.
• Notable hills include Sringirikhi (555 m), Durvasarshi (661 m), and Mahabar (549 m).
• These hills are named after saints such as Durvasa, Lomas, Gautam, and Sringi, who resided there.
• The region is home to Mohana and Kakolat waterfalls.

Rajgir Hilly Region

• Situated in the fertile alluvial plain of Central South Bihar, this region spans Nalanda and Gaya districts and is part of the Gaya hills extension.
• The hilly ranges stretch from Bodh Gaya and split into two parallel ranges near Giriak, enclosing the valley that once housed the ancient town of Rajgriha.
• These ranges meet again beyond Vaibhargiri and Saonagiri hills.
• Key hills include Vaibhavgiri (380 m), Bipulgiri (320 m), Ratnagiri (313 m), Udayagiri (231 m), Saonagiri (222 m), and Bihar Sharif/Pirpahari (108 m).
• Shanti Stupa is located east of Bipulgiri.
• The northern part of this region is lush and green, while the southern part is drier due to its rain shadow location. The hills consist mainly of quartzite and slate.

Munger Hilly Region

• Found in the southern areas of Jamui and Munger districts in Bihar.
• Features low ranges and isolated peaks, with the Kharagpur hills forming the most prominent range from Jamalpur to Jamui railway station.
• Gidheshwar hills, located in the southwest, are part of Nawada’s hill system.
• Satpahari Hill (542 m) is the highest in the west of this region.
• The Kharagpur hills near Kachu have hot springs.
• The Chakai plateau, near the southern border, is surrounded by hills and covered with jungles.
• This plateau is separated from the northern undulating tract by the Batia hill range, extending to the Hazaribagh plateau and Nawada border.

Geographical Regions of Bihar

A geographical region comprises areas with shared features such as climate, soils, vegetation, land use, settlement types, and socio-cultural elements.

Prof. Inayat Ahmad and Prof. Ram Pravesh Singh classified Bihar into 10 geographical regions based on natural and socio-cultural characteristics.

Terai Region

• The wettest region of Bihar, located in the northwest (Someshwar range and Ramnagar Doon of the Shiwaliks) and northeast (Araria and Kishanganj).
• Characterized by marshy land and dense forests, with paddy, jute, and sugarcane cultivation.
• The land is rugged, leading to temporary settlements.

Ghaghra-Gandak Doab

• A square-shaped alluvial plain in Saran, Siwan, and Gopalganj districts.
• Receives about 120 cm of annual rainfall.
• Noted for extensive sugarcane cultivation and a flourishing sugar industry.

Gandak-Kosi Doab

• Covers Sitamarhi, Sheohar, Begusarai, Darbhanga, Muzaffarpur, Vaishali, and Madhubani districts.
• The region supports sugar, fruit-processing, and dairy industries, with industrial hubs like Barauni.

Kosi-Mahananda Doab

• Includes districts like Madhepura, Saharsa, Khagaria, Kishanganj, Araria, and Purnea.
• Prone to flooding due to high rainfall, limiting industrial and agricultural development.

Karmanasa-Son Doab

• Covers Bhojpur, Kaimur, and Buxar districts.
• Receives low rainfall; irrigation is canal-based.
• Known for extensive paddy cultivation and rice mills.

Son-Kiul Doab

• Found in southern Bihar districts such as Patna, Jehanabad, Arwal, Nawada, Lakhisarai, Aurangabad, Nalanda, and Gaya.
• Often faces drought due to low rainfall.
• Hosts industries like silk-textile, cement, edible oil, and handicrafts.

East-Central Bihar Plain

• Spans Bhagalpur, Munger, and Banka districts.
• Agriculture and industry are underdeveloped, except for silk-textile in Bhagalpur and tobacco and dairy industries in Munger.

Ganga-Diara Region

• Formed annually by floodwaters, covering areas along the Ganga River, including Buxar, Bhojpur, Saran, Vaishali, Samastipur, Begusarai, Munger, Patna, Lakhisarai, Bhagalpur, and Katihar.
• Known for Rabi and vegetable crops.

Kaimur Plateau

• Located in Kaimur and Rohtas districts in southwest Bihar.
• Known for stone-based industries, pyrites-based sulphur industry in Amjhore, and limestone-based cement industry in Banjuri.

Mica Region

• Found in Munger, Jamui, Gaya, and Nawada districts.
• Mica exists as Balthar soil, and the region supports timber, silk, and lac industries.

Important Mountain Peaks/Hills of Bihar