Question

how the northern plains can be divided on the basis of variations in relief features

Answer 1

The Great Northern Plains of India can be divided into 6 subregions on the basis of relief... 
1.The Rajasthan Plains 
2.Punjab-Haryana Plains 
3.Upper Ganga Plains 
4.Middle Ganga Plains 
5.Lower Ganga Plains 
6.Brahmaputra Plains 
Elevation of Rajasthan Plains is higher than Punjab-Haryana and Ganga Plains.The slope descends from West to East.Brahmaputra Plains are located at a higher elevation compared to Lower Ganga Plains.