Duns are narrow longitudinal valleys that are formed between the Shivalik hill and the lesser Himalayas. They are formed by the deposition of sediments such as thick gravel and alluvial soil at the bottom of the river water. Duns are usually established under the Himalayan River with coarse alluvium present with it. The valleys are accumulated with coarse alluvium passed down by Himalayan rivers. Duns are mostly made of rock and alluvial soil and have a small size. They are filled with gritty alluvium that flows close to the streams coming from the Himalayas. The shape of duns is narrow and they are made of alluvial soil and gravel. Duns are also known as Dims and are used as a local word for valley or open valley. Examples of duns include Kotli Dun, Dehra Dun, and Patli Dun.