The physiographic divisions of Assam include the Brahmaputra Valley, Barak Valley, Karbi Plateau, and the Barak Hills.
The physiographic regions of the Brahmaputra Valley are the northern plains, southern plains, and the riverine floodplains.
North-bank tributaries: Subansiri, Jia Bharali, Dhansiri, Manas.
South-bank tributaries: Kopili, Barak, Burhi Dihing, Disang.
The Brahmaputra plain region is a vast alluvial plain formed by the Brahmaputra River and its tributaries. It features fertile soil, extensive wetlands, and is prone to seasonal flooding, supporting agriculture and rich biodiversity.
The floodplain region of the Brahmaputra is a low-lying area along the river, characterized by frequent flooding that deposits fertile silt, creating fertile land for farming but also causing seasonal waterlogging.
Majuli is a river island in the Brahmaputra River, located in Assam, India. It is formed by the deposition of silt and sediment by the river, making it one of the largest river islands in the world.
The Barak Valley is bordered by the states of Manipur, Mizoram, and Tripura, and features a mix of plains and hills with dense forests, tea gardens, and a humid climate.
The Karbi Plateau is surrounded by the Brahmaputra Valley and features rugged terrain, dense forests, and a cooler climate compared to the plains, with a rich tribal cultural heritage.
The Barail Range and Southern Hills are characterized by rugged topography, dense evergreen forests, and a diverse wildlife population, serving as a natural barrier in southern Assam.
Assam has a subtropical monsoon climate, characterized by high humidity, heavy rainfall during the monsoon season, warm summers, and mild winters.
The main reason for rainfall in Assam during the summer season is the southwest monsoon winds that bring heavy precipitation to the region.
Geographical factors influencing Assam's climate include its location in the northeastern part of India, the surrounding hills that trap monsoon winds, and the Brahmaputra River system that affects local humidity and rainfall patterns.
The main seasons of Assam are pre-monsoon, monsoon, and post-monsoon. Seasonal variations include high rainfall and warm temperatures during the monsoon, moderate rainfall and temperatures in the pre-monsoon, and cooler, drier conditions in the post-monsoon period.
The highest rainfall is witnessed in Mawsynram (around 11,872 mm annually), and the lowest is in Silchar (around 2,800 mm annually).
The amount of rainfall varies due to differences in altitude, the presence of hills that cause orographic rainfall, and the distance from the Bay of Bengal where monsoon winds originate.
The spatial distribution of rainfall in Assam shows higher precipitation in the eastern and southern hilly areas, decreasing towards the western plains due to varying topography and monsoon influence.
Assam has alluvial soil in the plains, red and laterite soil in the hills, and sandy soil along riverbanks, each supporting different agricultural activities.
Soil erosion in Assam is caused by heavy monsoon rains, deforestation, shifting cultivation, and the Brahmaputra River's strong currents.
The different types of forests in Assam include tropical evergreen, semi-evergreen, moist deciduous, and swamp forests.
A rainforest is a dense forest with high rainfall. In Assam, rainforests are characterized by tall trees, rich biodiversity, high humidity, and a multi-layered canopy.
Riverine vegetation in Assam is important for stabilizing riverbanks and supporting aquatic life. It includes grasses, reeds, and trees adapted to wet conditions.
Kaziranga National Park is located in Assam, India, covering an area of approximately 430 square kilometers.
The national parks of Assam are Kaziranga National Park (Nagaon and Golaghat districts), Manas National Park (Baksa, Chirang, and Bhutan border), and Orang National Park (Darrang and Sonitpur districts).
Wildlife sanctuaries in Assam maintain ecological balance by protecting diverse species, preserving habitats, and preventing overexploitation of natural resources.
Post-independence, Assam's administrative boundaries changed with the creation of new states like Meghalaya, Mizoram, and Nagaland from its territory, and further reorganization over time.
Assam's present districts include Kamrup (Guwahati), Nagaon (Nagaon), Jorhat (Jorhat), and others, each with its respective headquarters.
Assam has a land area of approximately 78,438 square kilometers, with its capital at Dispur. The largest district by area is Karbi Anglong, and the smallest is South Salmara-Mankachar.
The population of Assam according to the 2011 Census is about 31.2 million. The largest district by population is Nagaon, and the smallest is Dima Hasao.
(a) Assam and Monsoon Climate: Assam experiences a monsoon climate with heavy rainfall from June to September due to southwest monsoon winds.
(b) South-West Monsoon Wind: These winds bring the bulk of Assam's rainfall, originating from the Bay of Bengal.
(c) North-East Monsoon Wind: These winds contribute less rainfall, mainly affecting the southern parts in winter.
(d) Summer Season of Assam: Marked by high temperatures and the onset of the monsoon, typically from March to May.
(e) Pre-Monsoon Season of Assam: A transitional period from February to May with rising temperatures and occasional showers.
(f) Spatial Distribution of Rainfall in Assam: Varies from high in the east to lower in the west due to topography.
(g) Administrative Divisions of Assam: Comprises 35 districts divided into several divisions for governance.
(h) District Level Population of Assam: Varies widely, with Nagaon being the most populous district.
(i) BTAD: Bodoland Territorial Area Districts, an autonomous region in western Assam.