Shivaliks constitute a long chain of narrow and low hills lying almost parallel to the main ranges of the Himalayas. Its altitude ranges from 300 to 600 m above sea level. The hill slopes are much steeper on the northern side while the slope is gentler and it gets merged to the flat floored structural valleys called 'duns' in the south. Major duns found in the region are Dehra, Kohtri, Chaukham, Patti and Kota. The dun of Dehra is the biggest with a length of 35 km and width of 25 km.