In the middle part of its course, a river, after crossing the mountainous and hilly regions, debouches into the plain. In the plain area and the slope is gentle, owing to which the river is slackened and becomes unable to carry the large-sized shingles, pebbles, gravel, and sand. Consequently, they start being deposited. This deposit is triangular in shape through which the river flows in several braided channels. This gently sloping accumulation of coarse alluvium deposited by a braided stream is known as alluvial fan or alluvial cone. These are built mostly during the rainy season, when the volume of water as well as the sediments are enormous.