Proluvial Fan Landscape
Reference work entry
When temporary floodwater flows out of a mountain pass in an arid or semi-arid region, the debris it carries is deposited to form a fan-shaped landscape that is called a proluvial fan landscape. Usually, there is no water in the river channels in the valleys in arid and semi-arid areas. The channel bed and valley sides accumulate debris that is eroded from the hills. During the onset of flash floods in the rainy season, the water in the valley rises and transports abundant debris downstreams. When the debris-laden flow reaches the mountain pass, where the gradient is gentle, its transportation capacity decreases drastically, so it deposits large amounts of gravel, sand and mud to form a depositional proluvial fan that extends from the hills to the plain (Fig. 28).
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