why are the plains thickly-populated?????
A lot of flat lands are available in plains. Also these plains are generally fertile. Hence, plains are the most useful areas for human habitation and as well as for cultivation. Transport network can also be easily constructed in plains. Thus plains are thickly populated.
The Northern plains lie to the south of the Himalayas.They are generally level and flat.These are formed by the alluvial deposits laid down by the rivers-the Indus,the Ganga ,the Brahmaputra and their tributaries.These river plains provide fertile land for cultivation.That is the reason for high concentration of population in these plains.