Q. The river valleys of the western, central and eastern regions of the Himalayan ranges show a great variation among themselves. With this reference, consider the following statements:

1. The valleys in the western Himalayas are deep, longitudinal & well drained; while the valleys of the eastern Himalayas are broad & relatively shallow
2. The valleys in western Himalayas are called doons, while in eastern Himalayas are called duars

Which among the above is / are correct statements?
Answer: Both 1 & 2
Notes: Himalayan rivers form part of the Antecedent Drainage system wherein the rivers flow in their original direction even after the upliftment of land across their course and result in deep valleys across the uplifted landmass. Most of them have their origins in Tibetan Highlands and flow across the Himalayas for considerable distance. Western Himalayas: Valleys are deep. They are longitudinal and are well-drained. e.g. Kashmir and Kathmandu etc. Eastern Himalayas Valleys are large, broad and relatively shallow due to erosion caused by rivers, raised water levels from monsoonal rains and a less resistant sedimentary rock bed lying underneath. Central Himalayas: Broad, flat and structural valleys better known as ‘duns’ in west and ‘duars’ in eastern ranges. E.g. Dehradun, Kothari Dun and Patli Dun etc.