An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but are also found in more humid environments subject to intense rainfall and in areas of modern glaciation. They range in area from less than 1 square kilometer (0.4 sq mi) to almost 20,000 square kilometers (7,700 sq mi).
Alluvial fans typically form where flow emerges from a confined channel and is free to spread out and infiltrate the surface. This reduces the carrying capacity of the flow and results in deposition of sediments. The flow can take the form of infrequent debris flows or one or more ephemeral or perennial streams.
Alluvial fans are common in the geologic record, such as in the Triassic basins of eastern North America and the New Red Sandstone of south Devon. Such fan deposits likely contain the largest accumulations of gravel in the geologic record. Alluvial fans have also been found on Mars and Titan, showing that fluvial processes have occurred on other worlds.
Some of the largest alluvial fans are found along the Himalaya mountain front on the Indo-Gangetic plain. A shift of the feeder channel (a nodal avulsion) can lead to catastrophic flooding, as occurred on the Kosi River fan in 2008.
An alluvialfan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment...
stream bed, on a floodplain, in an alluvialfan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is typically...
The Okavango Delta (or Okavango Grassland; formerly spelled "Okovango" or "Okovanggo") in Botswana is a vast inland delta formed where the Okavango River...
An alluvial plain is a plain (a largely flat landform) created by the deposition of sediment over a long period of time by one or more rivers coming from...
long been subject to mudslides and flooding. Deposits preserved on the alluvialfan deltas here show that geologically similar catastrophes have occurred...
form enormous fan-shaped accumulations called submarine fans on both the continental slope and continental rise. Alluvial or sedimentary fans are shallow...
on flow, alluvial diagrams are named after alluvialfans that are naturally formed by the soil deposited from streaming water. In an alluvial diagram,...
Water use in alluvialfans refers to irrigation systems using the water resources in alluvialfans, mainly river floods and groundwater recharged by infiltration...
Tectonic forces have been shown to have major influences on alluvialfans. Tectonic movements such as tectonic uplift are driving factors in determining...
drainage and soil salinity control in the alluvialfan of Garmsar The irrigation system for the alluvialfan of Garmsar is quite well developed (Fig. G1...
turbidity currents. They can be thought of as an underwater version of alluvialfans and can vary dramatically in size, with widths from several kilometres...
mountains, hills, and uplands. Frequently foothills consist of alluvialfans, coalesced alluvialfans, and dissected plateaus. Foothills primarily border mountains...
Talgar (Kazakh: Талғар, romanized: Talğar, pronounced [tɑlˈʁɑɾ]; Russian: Талгар) is a town in Almaty Region, southeastern Kazakhstan. It is the administrative...
Subprefecture. Sapporo lies in the southwest of Hokkaido, within the alluvialfan of the Toyohira River, which is a tributary stream of the Ishikari. It...
alluvialfan meets the mountains or foothills; water is more abundant in the mountains because of orographic lifting and excavation in the alluvial fan...
continental environments are lagoons, lakes, swamps, floodplains and alluvialfans. In the quiet water of swamps, lakes and lagoons, fine sediment is deposited...
Creek alluvialfan, which began long before the lake had reached its highest level, added to the instability and ultimate collapse of the fan-dam. The...
materials are deposited, leaving a mound of conical shape. While an alluvialfan is formed when flowing water rushes rock and soil down a slope, debris...
Putangirua Pinnacles, formed by the erosion of the conglomerate of an old alluvialfan – is located at the head of a small valley near the southern tip of the...
extensive alluvialfan that extended out from the ancestors of the Musgrave, Mann and Petermann Ranges to the south and west, but separate from a nearby fan that...
An alluvial megafan is a large cone or fan-shaped deposit built up by complex deposition patterns of stream flows originating from a single source point...
form a symmetrical fan shape. Alluvialfan deltas, as seen by their name, avulse frequently and more closely approximate an ideal fan shape. Most large...
Islands found on the River Thames and its tributaries in England Alluvialfan – Fan-shaped deposit of sediment Anabranch – A section of a river or stream...
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