Siwalik is highland region in between the Mahabharat and Chure mountain range inNepal.

This region has deposit of huge quantity of calcium carbonate and sub-economic grade of important minerals such as iron, sulfur, copper etc. The tectonically active zone of the Himalaya, Siwalik Hills are considered as the most dynamic formation where they annually rise up by 3 to 4 mm. Being very young in geological formation and tectonically active, the hills exhibit a very conspicuous fragile terrain. They stretch east west following a belt of merely 15-20 km in width, forming the north boundary of plains of Terai and southern boundary of Middle-hill Mountains.

The region is extremely important because of mainly two reasons: one is, it is the prime source of sediments, which a number of steep gradient torrents transport downstream to the plain of Terai. It leads to the rise of streambed level further aggravating the flooding and inundation problems in the plains. The other one is, the region is rich in a thick sub-tropical forest resource. The first reason is concerned over the need to protect the area from further degradation in order to protect the downstream low land plains, which serve more than 80% of the food supply to the country