PHYSIOGRAPHY

A bird’s eye view shows that the entire area of Assam can be broadly divided into three well-defined geographical units --- the Brahmaputra Valley covering the main body of the State in the north, the Barak Valley in the narrow protruding south and the state’s hilly region that separates the two valleys. The Red River and its Valley: The alluvial Brahmaputra Valley which commands a lion’s share of the territory is the result of the erosional and depositional work of the river Brahmaputra and its many tributaries.  It is a flat

plain with a slope of only 12cms every kilometer,80-100km wide

in its upper reaches, narrow almost by half in the area where it passes the hilly region which demarcates it from the Barak Valley, and ballooning out again to form the as wide Kopili plains in the west.

The 724 km-flow of the Brahmaputra through the entire length of the valley with more than a hundred tributaries flowing down from the surrounding hills to merge with it, is a spectacular phenomenon. Once the tributaries hit the valley, they lose their momentum, deposit the silt they carry, form ox-bow lakes and alluvial fans and branch out before picking up their courses again to join the Brahmaputra

The Brahmaputra itself is no less capricious. Due to the low slope of the land it flows through, it tends to meander and form riverine islands.Majuli, the largest of these islands with an area of 929 sq km, is deemed to be the biggest riverine island in the world. But it is also a temperamental river. If on one hand it brings rich and fertile soil to its valley, on the other, it overflows its banks and causes destructive floods during the rainy seasons

The sluggish river of the dry winter months turns into a raging torrent during the rainy summers. And with all its natural vagaries, the magnificient Red River forms one of the most majestic river systems in the world. The Assamese call it Luit and call themselves Luitporias --- such is the bond between river and people.

The Barak Valley: The Barak plays a similar role in the south though on a much smaller scale. The Barak Valley is a swampy plain interspersed with low hills. Like the Brahmaputra, the Barak has also created a fertile valley and is given to destructive floods during the rainy seasons. The Sonai and the Dhaleswari are two important tributaries of the Barak.

 The Hilly Region:

The hilly region separating the Brahmaputra Valley in the north and the Barak Valley in the South itself consists of highly rugged and dissected terrain in the north and the south with the central plains of the valleys of the tributaries of the Brahmaputra --- the Kapili, Jamuna and Dhansiri --- wedged in between. In the north the region rises abruptly from the surrounding plains, while in the north it merges with the eastern flanks of the Jaintia Hills and the northern flanks of the Barail range. The height of the region varies from 1,000 km to 1,200 km above mean sea level. The North Cachar Hills  and Karbi Anglong districts are located in this region.