Alluvial Fan

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alluvial fan

[ə′lüv·ē·əl ′fan]
A fan-shaped deposit formed by a stream either where it issues from a narrow moutain valley onto a plain or broad valley, or where a tributary stream joins a main stream.

Alluvial Fan


a type of relief in the form of a slightly convex fan, formed through the accumulation of loose detrital material in the estuarine part of temporary streams and small rivers where they emerge from mountains onto piedmont plains or from gorges onto broader valleys. It forms as the result of the deposition of material suspended in water when the speed of the current of water decreases owing to a change in gradient. Populated areas are frequently situated on alluvial fans.

References in periodicals archive ?
Alluvial fans are cone-shaped deposits of gravel and sand that accumulate where streams exit mountains.
indicate the existence of complex processes of change in the landscape of the Pantanal, resulting from the sedimentary dynamic in alluvial fans.
The wood stakes and branches are from mesquite (Prosopis laevigata), granjeno or desert hackberry (Celtis pallida) and huisache (Acacia farnesiana), species that are abundant inside and outside the alluvial fan.
The basal unit is the Honeycomb Point Formation, which is dominated by breccia, sandstone, and minor shale that record deposition mainly on alluvial fans.
The gentle alluvial fan of the Preak Tnaot was also generally not inundated, except for its low-lying eastern skirt (within Phnom Penh city).
4) A very large aeolian unit west from the ranges and south from the Lachlan Alluvial Fan to Goolgowi in the south.
This caused over- bank flow for nearly 100 m upstream of the debris jam at the Lalio site, which deposited nearly 20 cm of sand on parts of the alluvial fan.
Potter (1955) considers them to be the remains of a series of coalescing alluvial fan deposits from the ancestral Tennessee, Cumberland, and Mississippi Rivers.
It sits on the Kern River alluvial fan, which was created by deposition of sediment on the valley floor.