Alluvial plain

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					Alluvial plain
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An alluvial plain is a largely flat landform created by the deposition of sediment
over a long period of time by one or more rivers coming from highland regions, from
which alluvial soil forms. A floodplain is part of the process, being the smaller area
over which the rivers flood at a particular period of time, whereas the alluvial plain
is the larger area representing the region over which the floodplains have shifted
over geological time.
As the highlands erode due to weathering and water flow, the sediment from the
hills is transported to the lower plain. Various creeks will carry the water further to a
river, lake, bay, or ocean. As the sediments are deposited during flood conditions in
                                                                                                  A small, incised alluvial plain from Red
the floodplain of a creek, the elevation of the floodplain will be raised. As this
                                                                                                   Rock Canyon State Park (California)
reduces the channel floodwater capacity, the creek will, over time, seek new, lower
paths, forming a meander (a curving sinuous path). The leftover higher locations,
typically natural levees at the margins of the flood channel, will themselves be eroded by lateral stream erosion and from local
rainfall and possibly wind transport if the climate is arid and does not support soil-holding grasses. These processes, over
geologic time, will form the plain, a region with little relief (local changes in elevation), yet with a constant but small slope.
The above description seems to fit with the primary definition found in the "Glossary of Landform and Geologic Terms",
maintained by the National Cooperative Soil Survey, which states that an "alluvial plain" is "a large assemblage of fluvial
landforms (braided streams, terraces, etc.,) that form low gradient, regional ramps along the flanks of mountains and extend
great distances from their sources (e.g., High Plains of North America)" Use of "alluvial plain" as a general, informal term for a
broad flood plain or a low-gradient delta is explicitly discouraged. The NCSS glossary instead suggests "flood plain".[1]

   Babylonia, Iraq
   Mississippi River alluvial plain [2]
   Oxnard Plain, Ventura County, California
   Padan plain, Italy.
   Punjab alluvial plain [3]
   Laguna de Santa Rosa
   Christchurch, New Zealand
   List of alluvial sites in Switzerland

See also
   Alluvial desert
   Alluvial fan
   River delta

   1. ^
   2. ^ Mississippi River alluvial plain
   3. ^ Punjab Plain , Encyclopædia Britannica

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