Class 9 Social Science Geography Chapter 4 Geography of Assam

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Class 9 Social Science Geography Chapter 4 Geography of Assam The answer to each chapter is provided in the list so that you can easily browse throughout different chapters Assam Board Class 9 Social Science Geography Chapter 4 Geography of Assam and select needs one.

Class 9 Social Science Geography Chapter 4 Geography of Assam

Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board SEBA Class 9 Social Science Geography Chapter 4 Geography of Assam Solutions for All Subject, You can practice these here.

Geography of Assam

Chapter: 4


Textual questions and answers Exercise:

Q.1: What are the physiographic divisions of Assam?

Ans: Assam is a land of biodiversity. Assam’s unique climatic and landforms variation from east to west and from north to south supports a wide variety of flora and fauna.

The four main physiographic divisions of Assam are:

(i) The Brahmaputra Valley.

(ii) The Barak Valley.

(iii) The Karbi Plateau.

(iv) The Barail and Southern hills.

Q.2: What are the physiographic regions of the Brahmaputra Valley?

Ans: The present physiographic configuration of Assam is geologically of recent origin. It is characterized by diverse features such as floodplains, marshes and heels, scattered hillocks, folded hill ranges and old plateaus.

The main physiographic units of the Brahmaputra valley are:

(i) Northern foothills, (ii) the north and south bank plains. (iii) the flood plains and charlands, (iv) the southern foothills.

Q.3: Write four names each of the north-bank and south-bank tributaries of the Brahmaputra river.

Ans: (i) North-bank tributaries: Subansiri, Ranganadi, Buroi and Borgong.

(ii) South-bank tributaries: Burhi Dihing, Dikhow, Disang and Jhanzi.

Q.4: Give a brief description of the Brahmaputra plain region.

Ans: The Brahmaputra is a trans-boundary river which flows through Tibet (China), Northeastern India, and Bangladesh. It is known as Brahmaputra or Luit in Assamese, Yarlung Tsangpo in Tibetan, the Siang/Dihang River in Arunachali and Jamuna River in Bengali. The Brahmaputra plain region was formed due to the deposition of alluvial sediments carried by the Brahmaputra and its tributaries from the northern and southern hills and highlands. The region is composed of alluvial soil which are suitable for agriculture. The region is highly populated  and has a well-developed transport system. 

When the Brahmaputra River moves into the Assam plain, it becomes a braided river and together with its tributaries, forms the drainage area of the Brahmaputra Basin. The breadth of the Brahmaputra Basin in Assam is about 80 to 100 km and the length is approximately 1,000 Km.

The north and south Bank plains composed of alluvial soils are suitable for agriculture. This region is thickly populated and developed in transportation. The north bank plain is relatively wide with an average width of 30 km in the lower part and narrow in its upper part with an average width of about 10 km.

On the other hand the south bank plain is only about 5 km wide in the. districts of Kamrup, Goalpara and Dhubri due to extension of the Meghalaya Plateau. But it is somewhat wide from the east of Guwahati to the Kopili plain. Again, the plain has become narrow in the western parts of Nowgong and Golaghat districts due to northward extension of the Karbi Plateau.

However, it is again wide from the eastern part of the Golaghat district upto Tinsukia district through the districts of Jorhat, Sibsagar and Dibrugarh. It is because of the headward erosion of the rivers like Dhansiri, Dikhow, Burhi Dihing. Dibru etc of the south bank plain has become wide. Like the north bank plain, the south bank plain is also thickly populated. It is suitable for agriculture due to its fertile lands. The transport system is also developed here.

Q.5: Give a brief description of the floodplain region of the Brahmaputra.

Ans: The region situated between the north bank and south bank plains, where occasioned and frequent floods are caused by the Brahmaputra river is known as the floodplain of the Brahmaputra.

This floodplain naturally includes the charlands developed on the bed of the Brahmaputra. The width of the floodplain is not same at all places. Its width decreases due to the existence of some hillocks at certain places on the banks and also because of formation of levees along the banks of the river Brahmaputra. The floodplain on the north bank, especially in the districts of Dhemaji and Barpeta is characterised by a number of wetlands and swamps.

On the other hand, the south bank floodplain is comparatively narrow. However, it is somewhat wide near the confluence areas of Burhi Dihing. Disang, Dhansiri, Kolang-Kopili and Kulshi rivers. 

All the branching channels within the Brahmaputra river along with the chars (sandbars) and the charlands are altogether known as active floodplain.

Q.6: Write about the geographic location and origin of Majuli.

Ans: With a total area of 352 square kilometres (136 square miles), “Majuli” is the world’s largest river island and it attracts tourists from all over the world. It is an island in the Brahmaputra River, Assam and in 2016 it became the first island to be made a district in India. 

The island is formed by the Brahmaputra river in the south and the Kherkutia Xuti, an anabranch of the Brahmaputra, joined by the Subansiri River in the north. Mājuli island is accessible by ferries from the city of Jorhat.

Q.7: Write briefly about the boundaries and characteristics of the Barak valley.

Ans: The boundaries of the Barak Valley are: North-Meghalaya plateau and Barail ranges the North Cachar Hills, East-Manipur Hills, South-Mizo, West- Kushiyara-Surma plain of the Sylhet district of Bangladesh.

The characteristics of the Barak Valley are:

(a) The Barak valley region consists of the Barak plain and its adjacent northern and southern foothills. The river Barak flows for a distance of 225 km in Assam from east to west through Cachar district and along the northern boundary Hailakandi and Karimganj districts.

(b) The Barak plain has been created through deposition of alluvial sediments carried by the river Barak and its tributaries from the hills in the north and the south. This plain is also known as Cachar plain. 

(c) It is enclosed by hill ranges on its northern, southern and eastern sides. These are Meghalaya Plateau and the Barail ranges of the North Cachar Hills district on the north. Manipur hills on the east and the Mizo hills on the south. However, this plain is open on the west merging with the Kushiyara-Surma plain of the Sylhet district of Bangladesh.

(d) The important north bank tributaries of the Barak river are Chiri, Diksa, Digli, Jiri, Madhura, Jatinga, Larang etc. Its important south bank tributaries are Sonai, Dhaleswari-Katakhal, Singla, Langai etc. 

(e) The forest of the Barak plain are also rich in wild animals like elephants, antelope, deer, monkey, hoolock gibbon, tiger, pangolin etc.

Q.8: Write briefly about the boundaries and characteristics of the Karbi plateau.

Ans: The boundaries of the Karbi Plateau are: Northern- Brahmaputra plain, Southern- Barak plain, Eastern-Nagaland, Western- Meghalaya. The characteristics of the Karbi Plateau are: 

(a) Based on its origin and geographical formation the Karbi Plateau can be said to be a part of the Meghalaya.

(b) The Kopili valley has divided the Karbi plateau into two parts the eastern part and the western part. The eastern part covered by the Rengma hills spans over the entire Diphu and Bokajan sub-divisions of Karbi Anglong district. It is approximately double the size of the western part. 

(c) On the other hand, the western part covers the Hamren sub-division of the district. This part has an average height of 900m and it slopes from south-west to north-east. The physiography of this part of the Karbi plateau has developed as a result of the works of the rivers Kopili and Barapani and their tributaries.

(d) The north Cachar Hills district falls directly under the path of the south-west monsoon winds. So the district receives a higher amount of average rainfall.

(e) The hill region is extremely backward in industrial activities.

Q.9: Write briefly about the characteristics of the Barail range and southern hills.

Ans: The Barail Range is a mountain range located in the northeastern part of India, specifically in the states of Assam, Nagaland, and Manipur.

The characteristics of the Barail range and southern hills are: 

The part of the Barail range extending westward from Thensang across Nagaland spans over the North Cachar Hills district of Assam. Actually, the Burial range has connected the Naga hills in the east with the Meghalaya Plateau in the West. This range has also divided the North Cachar Hills region into two parts. The north-sloping part falls within the Brahmaputra valley, while the south-sloping part falls within the Brahmaputra valley.

The north-sloping part is relatively lower than the south-sloping part.

Q.10: What is the type of Assam’s climate? Write briefly about its characteristics.

Ans: The climate of Assam is typically ‘Tropical Monsoon Rainforest Climate’, with high levels of humidity and heavy rainfall. People here enjoy a moderate climate all throughout the year, with warm summers and mild winters.

The characteristics of the Assam climate are: 

(a) The state of Assam witnesses heavy rainfall in the summer season of the year, dry condition in winter season and almost always excessive humidity and relatively somewhat low temperature.

(b) Although the climate of Assam is basically influenced by monsoon wind, its geographical variations have made the climate quite diverse, Variations in geographic location, topography, water surface area of Arabian sea, Bay of Bengal and Indian ocean, and south-west monsoon wind, etc. have made the climatic characteristics of the state quite different in different places.

(c) The impact of seasonal variations in changing air pressure of the north-west Indian landmass can also be observed in the state’s climate. Besides, the presence of local winds like mountain wind, valley wind and rivers including other wetlands greatly influences the local climatic characteristics of the state.

(d) Generally, the air temperature of the Brahmaputra and Barak valley regions remains slightly higher than the neighbouring hill region. It is because of this a kind of low pressure is formed locally in the plains during summer season.

Q.11: What is the main reason behind the occurrence of rainfall in Assam during summer season?

Ans: The climate of the plains and the sub-montane region becomes unpleasant, especially in the summer season. It happens to be so because of the extreme humidity which comes with the monsoon.

Q.12: Discuss briefly about the geographical factors influencing the climate of Assam.

Ans: With the ‘Tropical Monsoon Rainforest Climate’, Assam is a temperate region and experiences heavy rainfall and humidity.

The geographical factors influencing the climate of Assam are:

(i) Variations in geographic location.

(ii) Topography.

(iii) Water surface area of Arabian sea, Bay of Bengal and Indian Ocean.

(iv) South-west monsoon wind.

(v) Variations in changing air pressure of north-west India due to change in seasons.

Q.13: What are the main seasons of Assam? Write in brief about the seasonal variation in the distribution of temperature and rainfall in Assam.

Ans: People here enjoy a moderate climate all throughout the year, with warm summers and mild winters. Spring (March-April) and autumn (September-October) are usually pleasant with moderate rainfall and temperature.

The main seasons of Assam along with the variation in temperature and rainfall are:

(i) Pre- monsoon season: in Assam prevails during early March to the end of May. As this season starts immediately after winter, since the beginning the atmospheric temperature starts increasing slowly.

During the period of pre-monsoon the morning is pleasant, scorching mid-day, tiring afternoon, and sudden rainfall with lightning and thunder sometimes in the evening or night. Some kind of ustable atmospheric condition prevails during this season and sometimes dust storms and rainfall with thunder occur. With the passage of time high amount of rainfall starts occurring more frequently. Occurrence of this rainfall before monsoon helps in the cultivation of paddy, tea and jute in the state.

(b) Monsoon: Monsoon season generally prevails during early June to end of September in Assam. This is the rainy season in Assam. During this period moderate to heavy rainfall occurs under the influence of south-west monsoon wind almost continuously in different places of the state. June, July and August are the months of maximum rainfall during monsoon.

The total annual rainfall in Assam (on the average about 200 cm) about 70, percent occurs during these three months only. During this monsoon Assam’s main crop Sali peddy is transplanted. Besides, due to the occurrence of heavy rainfall in most parts of the state including the surrounding hilly areas the water level of the Brahmaputra and Barak and their tributaries rises and often create floods.

(c) Retreating Monsoon: The south-west monsoon wind starts with drawing from the end of September. It means there is decrease of temperature and drawing from the end of September. It means there is decrease of temperature and rainfall in this season following the end of rainy season. As a result of decreasing temperature air pressure in the state begins to increase and thereby the wind direction completely gets reversed and blows from north-east to south-west. This is called north-east monsoon or retreating monsoon.

Generally retreating monsoon season prevails in Assam during October and November for two months. During this time period formation of fogs occurs in the night and morning due to temperature decrease.

(d) Dry winter: Winter season prevails in Assam during the end of November or beginning of December to the end of February. The characteristics of winter season in Assam are low temperature (below 10° C) thick clouds in the morning, and a very dry condition due to lack of rainfall. That is why the months of December and January are very dry and the month of January is too cold. During this winter season Sali paddy is harvested and Bhogali or Magh Bihu is celebrated.

Q.14: Write the names of places in Assam witnessing the highest and lowest rainfall along with the amount of rainfall.

Ans: The place in Assam that witnesses the highest and lowest  annual rainfall are:

PlaceAmount of Annual Rainfall (cm)
HighestNorth Lakhimpur335

Q.15: Why is the amount of rainfall not uniform in all places of Assam?

Ans: Rainfall levels in Assam differ from one place to another due to the different geographical formations and weather existing in the region.

The amount of rainfall is not uniform in all places of Assam due to (a) Topographic condition, (b) Location, (c) Presence of hills in the neighbouring areas.

Q.16: Write in brief about the spatial distribution of rainfall in Assam?

Ans: The temperature difference between winter and summer in a year. On the average the amount of temperature in winter is 7°C and in summer it becomes 35°C. On an average the state receives annual rainfall of about 200 cm. Of course, a study of the pattern of occurrence of rainfall in different places of Assam reveals that there exists marked spatial variation in rainfall across the state. Due to the overall impact of the state’s topographic condition, location and presence of neighbouring hills the distribution of rainfall in the state is quite uneven. Generally occurrence of rainfall is more in the hills and foothill areas. Besides, annual rainfall exceeds 250 cm in the districts of Tinsukia, Dibrugarh, Dhemaji, Lakhimpur and Sivasagar in upper Assam; Kokrajhar and Dhubri districts of lower Assam; and Cachar, Karimganj and Hailakandi districts of southern Assam.

On the other hand, amount of rainfall is quite less in Nagaon and Karbi Anglong districts of central Assam. It is worth mentioning that the Lanka-Lumding region of Nagaon district receives annual rainfall of 129 cm only.

Name of PlaceAverage Annual Rainfall (cm)
1. Guwahati166
2. Dhubri256
3. Barpeta229
4. Goalpara242
5. Nalbari242
6. Manaldoi181
7. Rangia190
8. Tezpur182
9. Nagaon203
10. North Lakhimpur335
11. Dibrugarh273
12. Sivasagar250
13. Haflong227
14. Jorhat227
15. Lumding129
16. Silchar323

Q.17: Give a short account of different types of soil found in Assam.

Ans: Soil is one of the vital elements of the physical environment. It is composed of both organic and inorganic materials.

The soils of Assam can be classified into four types. These are: (a) Alluvial Soil, (b) Piedmont soil (c) Hill soil (d) Laterite soils. 

(a) Alluvial Soil: The alluvial soils are extensively found in the plains of the Brahmaputra and Barak Valley. These soils have formed as a result of deposition of silt and clays carries by the rivers and their tributaries. Alluvial soils are generally fertile. These are two types-(a) New alluvial soils and (ii) Old alluvial soils. 

(i) New Alluvial soils: The new alluvial soil are mostly found in the active floodplains of the Brahmaputra and Barak rivers and their tributaries and also in the river side plains. These soils are moderately deep and gray in colour. These are basically composed of sandy to silty loams and slightly acidic. On the river banks, these are sometimes neutral or slightly alkaline.

These soils are deficient in phosphoric acid, nitrogen and humus. 

(ii) Old Alluvial soils: The old alluvial soils are found especially in the regions between the northern piedmont zone of the Kokarjhar, Barpeta. Nalbari, Kamrup, Darrang, Sonitpur, Lakhimpur and Dhemaji districts and the new alluvial soils of the south bank of the Brahmaputra.

Similarly these soils are found in the regions of the south bank districts lying between the southern hill soil zone and the new alluvial soil zone along the Brahmaputra river. Old alluvial soils occur extensively in the plains of the Kopili river in Nowgong district.

On the other hand, these soils are available in a narrow zone of the Barak plain between the active floodplain of Barak and the hill soils of the Assam- Mizoram border. Generally, the layers of the old alluvial soils are deep and brown in colour. These soils are more or less acidic and composed of fire to coarse loams.

(b) Piedmont soil: The piedmont soils are confined to the northern narrow zone along the piedmont zone of the Himalayan foothills. The piedmont zone consists of the Bhabar and the Tarai belts. The Bhabar belt extending in east-west direction along the Assam-Arunachal Pradesh border is formed by a series of alluvial cones. The soils of this belt are composed of unassorted materials of boulders, pebbles sands and silts. These soils have deep to very deep layers. On the other hand, the soils of the Terai belt occurring just south of the Bhabar belt generally remain saturated with water. These soils, therefore, support tall grasses.

(c) Hill soil: The hill soils are generally found in the southern hill areas of Assam. Fertility of hill soils differs from place to place. Nitrogen and organic materials are abundant in these soils. Based on physical structure and chemical properties, these soils can be divided into two types- (i) Red Sandy Soils and (ii) Red loamy Soils 

(i) Red Sandy Soils: The red sandy soils are found especially in the Assam-Meghalaya border region, Karbi plateau, southern part of the Barail range in the North Cachar Hills district and some parts of the foothills along the eastern boundary of the Cachar district. These soils are formed mainly

due to erosion of rocks and their layers are deep. These are strongly to moderately acidic with high organic content. 

(ii) Red loamy Soils: The red loamy soils are found in the narrow belt on the south of the Assam-Arunachal border, Karbi Plateau and also in the southern part of the Barail range in the North Cacher Hills district. These soils also occur in some amount, along the Assam-Mizoram border areas. The soils are deep and composed of fine to coarse sand, silt and clay. These soils are slightly to moderately acidic and these contain nitrogen, phosphoric acid, humus and lime in little amount.

(d) Laterite soils: The laterite soils are found in almost the entire North Cachar Hills district and in some southern parts of the Karbi Plateau. Moreover, these soils are also available in the eastern border of the Hamren sub-division of Karbi Anglong district, southern border of Golaghat district and the foothills of the Barail range in the northern part of the Barak plain. Generally, these sorts are black in colour and their texture is sandy. These soils contain less amount of nitrogen, potash, phosphoric acid and lime.

Q.18: What are the reasons behind soil erosion in Assam?

Ans: The soils of Assam are also affected by a number of physical and human factors. The physical and chemical properties of the solis are damaged by these factors, which finally cause soil degradation.

The physical factors are: (a) the soil erosion on the hill slope due to natural causes and (b) Water logging problems created on the plains and low-lying areas.

In the case of soil degradation, presently the human factors are more active than the physical factors. The major human factors of soil degradation are: (a) Surface soil erosion caused by increased surface water flow due to tree felling etc. (b) Cultivation of land on hill slope in unscientific manner, (c) Jhum cultivation done in the hill areas, (d) Water logging create as result of human settlement and after activities, (e) Use of chemical fertilizers in soils in order to increase more crop production.

Soil degradation is a burning problem. Soil are the base of the living kingdom and also a valuable element of the physical environment, Soils provide life-support to various plants and animal species, soils have been playing the vital and essential role in food crop production. So, soils are the valuable resource. All kinds of efforts should be made to protect the soils from degradation for their conservation.

Q.19: What are the different types of forests in Assam?

Ans: The word Assam has its origin in the Sanskrit word Asom meaning Unparalleled or Peerless. Forest type mapping using satellite data has been undertaken by the Forest Survey of India with reference to Champion and Seth Classification. As per this assessment, the state has 18 forest types belonging to five forest type groups viz Tropical Wet Evergreen, Tropical Semi Evergreen, Tropical Moist Deciduous, Tropical Dry Deciduous and Sub Tropical Pine Forests.

The forest of Assam can be divided into five types: (a) Tropical evergreen forest, (b) Tropical semi evergreen forest, (c) Tropical most deciduous forest, (d) Riverine forest, (e) Tropical dry deciduous forest.

Q.20: State the location and land area of Kaziranga national park.

Ans: The park is located between latitude 26°30 N to 26°45 N and longitude 93°08 E to 93°36 E in the Kaliabor subdivision of the Nagaon district and the Bokakhat subdivision of the Golaghat district, in the state of Assam in India. It is roughly 40 kilometres (25 mi) long and 13 kilometres (8 mi) wide, with an area of 378.22 km², having lost around 51.14 km² to erosion by the Brahmaputra. A total addition of 429 km2 (166 sq mi) along the present boundary of the park has been made and notified with separate national park status to provide extended habitat for increasing population of wildlife or as a corridor for safe movement of animals to Karbi Anglong Hills..

Q.21: Write the names and location of the national parks of Assam.

Ans: The names and location of the national parks of Assam are:

SL NoName of National ParksLocation
1.Kaziranga National ParkGolaghat and Nagaon and Sonitpur
2.Manas National ParkChirang and Baksa
3.Orang National ParkUdalguri and Sonitpur
4.Nameri National ParkSonitpur
5.Dibru-Saikhowa National ParkDibrugarh and Tinsukia
6.Dihang Patkai National ParkDibrugarh and Tinsukia
7.Raimona National ParkKokrajhar

Q.22: Write how the wildlife sanctuaries maintain the ecological balance.

Ans: Wildlife helps in maintaining the eco-logical balance of nature.

The contribution of wildlife sanctuaries in maintaining ecological balance are:

(a) The wildlife sanctuaries provides homes to wild elephants, tigers, rhinoceros, buffaloes, deer, monkey, one horn deer etc.

(b) Conserve biodiversity thorugh protecting these areas.

(c) Protect the animals from the destructive impact of human beings.

In Assam three are 18 wild life sanctuaries and two proposed WLS. They covering a total area of 3592.94 sq. km.

These protected areas are the home of wild elephants, tigers, rhinoceros, buffalos, a variety of deer, monkeys and other wild animals. With the presence of grasslands, trees and wetlands, these protected areas attract large number of domestic and foreign tourists. The future of biodiversity of our state lies, to a great extent, on the ability to protect these areas. The table mentioned in Q. No. 23 above provides an idea of the national parks and wildlife sanctuaries (WLS) of Assam.

Q.23: Write about the changes in administrative boundaries in Assam during the post-independence period.

Ans: Geographically, the spatial extent of Assam has witnessed marked change with time. Assam was quite large during the British rule. During that period besides Meghalaya and Nagaland, Sylhet (now in Bangladesh) was a part of Assam.

But in 1947, following India’s partition the Sylhet part was separated from Assam and joined East Pakistan (presently Bangladesh). Accordingly there were 11 districts in Assam and Shillong was its capital. In the latter period, three states, viz. Nagaland in 1963, Meghalaya in 1970 and Mizoram in 1971, got separated from Assam.

The capital city of Assam was established in Dispur (Guwahati) in 1973. Since 1971 till now (up to 2014) the area of Assam including its geographical boundary and spatial extent has remained the same. At present the state of Assam has land area of 78,438 km² and population of 31.16 million (According to 2011 Census).

In view of certain administrative advantages and constraints and fulfilling the hopes and aspirations of different ethnic groups inhabiting the state. some new districts have been constituted within the same spatial limit of the state.

At present there are altogether 27 districts in Assam. Among these 27 districts, four districts, viz. Kokrajhar, Chirang, Baksa and Udalguri fall under the BTAD (Bodoland Territorial Area Districts). In order to fulfil the hopes and aspirations of especially Bodo tribal groups this BTAD was formed in 2003.

In respect of land area, Karbi Anglong district is the largest (10,434 km²) and Kamrup Metropolitan district is the smallest (627 km²). On the other hand, in terms of population size, Nagaon district is most populous (2.8 million) and Dima Hasao district is the least populous (2.1 lakh).

Q.24: Write the names of the present districts of Assam and their headquarters.

Ans: The names of the present districts of Assam and their headquarters are:

Name of DistrictsHeadquarters
Kamrup MetroGuwahati
Karbi AnglongDiphu
LakhimpurNorth Lakhimpur

Q.25: What is the land area of Assam? Where is the state’s capital located? Write the names of the largest and smallest districts of Assam in respect of land area.

Ans: The land area of Assam is 78,438 sq km.

Assam’s capital is located at Dispur (Guwahati).

Largest districts: Karbi Anglong with an area of 10,434 sq km.

Smallest districts: Kamrup Metro with an area of 627 sq km.

Q.26: What is the population of Assam according to 2011 census? Write the names of the largest and smallest districts of Assam in terms of population size.

Ans: According to 2011 census, the population of Assam is 31.16 million. In terms of population size

Largest district of Assam is Nagaon with a total population of 2,826,006 (2.8million) and 

Smallest district is the Dima-Hasao with a total population of 213,529 (2.1 lakh).

Q.27: Write short notes:

(a) South-West monsoon wind

Ans: The South-west Monsoon: The Himalayan mountain range and its branches spreading on the north and east of the Brahmaputra and Barak valleys obstruct the warm and moist monsoon wind blowing from south- west in summer. It is called the South-West Monsoon Wind.

Besides, these mountain ranges also protect this state from the problem of excessive cold wind blowing from Tibetan plateau towards India in winter. On the other hand, the clouds carried by the south-west monsoon wind after crossing Meghalaya plateau and other southern hills result in heavy rainfall particularly in the north-eastern part of the Brahmaputra valley in summer. Moreover, the south-west monsoon wind, after getting obstructed by the hills surrounding the Barak valley region from three sides, also gives heavy rainfall in the Barak plains. Of course, depending on the variation in energy of the monsoon wind and amount of accompanying water vapour generally the amount of annual rainfall varies across the state.

The amount of rainfall significantly decreases on the leeward side of the hills particularly east of Karbi Anglong, and north and east of Dima Hasao. Due to similar reason the southern part of Nagaon district also receives very low rainfall. Of course, the amount of rainfall always remains high along- the foothills region of the Himalayas.

A branch of south-west monsoon wind after crossing the Meghalaya plateau and another entering the Brahmaputra valley from the west give considerable amount of rainfall in the lower Brahmaputra region. The summer rainfall of Assam occurs mainly due to the orographic and cyclonic processes of the moist south-west monsoon wind.

(b) North-east monsoon wind.

Ans: North-east monsoons: When winds moves back from the mainland to the Bay of Bengal, it is known as retreating monsoons. Retreating monsoons are also called as north-east monsoons. They start when withdrawal of southwest monsoons begin that is during September-November. On the other hand, relatively a low pressure condition prevails at that time in the Bay of Bengal. It is due to such a change in the pressure condition between summer and winter the direction of wind in winter becomes just opposite of the summer south-west monsoon wind. Hence, the wind that formed in the upper Brahmaputra valley in winter blows towards the Bay of Bengal is known as North-East Monsoon Wind or Retreating Monsoon. The dry north-east monsoon wind after absorbing some moisture from the Brahmaputra river and its tributaries sometimes in winter gives some amount of rainfall in south-western part of Assam. Otherwise amount of moisture in the atmosphere remains quite low during this winter season.”

(c) Administrative divisions of Assam.

Ans: Administrative Divisions of Assam: Just before independence Assam had 11 administrative districts and a large part of Arunachal Pradesh (then called ‘North-East Frontier Tract’) was administered through the Governor of Assam. Between 1947 and 1971 Naga Hills District became a state in the name of Nagaland, Garo Hills and United Khasi and Jaintia Hills also became a state of as ‘Meghalaya’ and ‘Lushai Hills’ became a Union Territory as Mizoram and went out of Assam. However, each of the remaining districts of Assam was found to be too large for implementation of new developmental measures, and hence the districts were reorganised from time to time. 

Thus there came into existence 23 districts in Assam, towards the end of the last century. After this as per Govt. of Assam’s notification dated October 30, 2003 [No GAG (B) 137/2002/PT/117), three new districts (Chirang, Bagsa and Udalguri) were constituted and one old district viz. Kokrajhar was reconstituted under Bodoland Territorial Council (BTC). These four districts are known as Bodoland Territorial Area District (BTAD). Then it was realised that the ever expanding Guwahati city should be constituted a separate district for its physical and social development. So the Greater Guwahati area including Sonapur, Digaru and Khetri parts was separated from Kamrup district and made Kamrup Metropolitan District. The remaining part lying in both the north and south banks came to be known as a separate Kamrup Rural District. Thus Assam now has 27 administrative districts.

(d) District level population of Assam.

Ans: District level population of Assam: The details analysis of population census 2011 published by govt. of India for Assam state reveal that population of Assam has increased by 17.7% in this decade compared to past decade. The density of Assam state in the current decade is 1030 per sq. mile. 

As per the 2011 census, the total population of Assam was 31,169,272. The total population of the state has increase from 26,638,407 to 31,169.272 in the last ten year with a grown rate of 16.93%. On the 32 districts eight districts registered a rise in the decadal population grown rate.

The detail analysis of population census 2011 published by govt. of India for Assam state reveal that population of Assam had increased by 17.07% in this decade compared to past decade. Dhubri district has recorded the highest population growth rate in Assam while Kokrajhar has recorded the lowest, according to the 2011 census.

The Dima Hasao district of Assam has the lowest population density in the state. As per India census 2011, the Dima Hasao district of Assam has a population density of 44 per sq. km. It means only 44 persons per square kilometer area.

(e) BTAD

Ans: BTAD is the acronym of Bodoland Territorial Area Districts (BTAD). BTAD refers to the area under the jurisdiction of Bodoland Territorial Council (BTC) in Assam. BTAD is the acronym of Bodoland Territorial Area Districts. BTAD refers to the area under to jurisdiction of Bodoland territorial council in Assam. Created under the sixth schedule of the constitution of India, BTAD consists of 4 districts.

(i) Kokrajhar (ii) Baksa (iii) Udalguri (iv) Chirang These districts were covered out of seven existing districts of Assam-

(i) Kokrajhar (ii) Bongaigaon (iii) Nalbari (iv) Barpeta (v) Kamurp (vi) Sonitpur (vii) Darrang.

The current capital of BTAD is Kokrajhar.

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