 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Alluvial plain" – news ·newspapers ·books ·scholar ·JSTOR(November 2024) (Learn how and when to remove this message) |
Analluvial plain is aplain (an essentially flatlandform) created by the deposition ofsediment over a long period by one or morerivers coming from highland regions, from whichalluvial soil forms. Afloodplain is part of the process, being the smaller area over which the rivers flood at a particular time. In contrast, the alluvial plain is the larger area representing the region over which the floodplains have shifted over geological time.
As the highlandserode due toweathering and water flow, the sediment from the hills istransported to the lower plain. Variouscreeks will carry the water further to a river,lake,bay, orocean. As the sediments are deposited during flood conditions in the floodplain of a creek, the elevation of the floodplain will be raised. As this reduces the channel floodwater capacity, the creek will, over time, seek new, lower paths, forming ameander (a curved path). The leftover higher locations, typically naturallevees at the margins of the flood channel, will be eroded by lateral stream erosion, 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 littlerelief (local changes in elevation) yet with a constant but slight slope.
TheGlossary of Landform and Geologic Terms, maintained by the United StatesNational Cooperative Soil Survey (NCSS), defines an "alluvial plain" as "a large assemblage of fluvial landforms (braided streams, terraces, etc.) that form a 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]
Alluvial plains have similar traits to ariver delta; however, the river delta will flow into a larger body of water. Alluvial plains generally don't have this.
| Large-scale features | |
|---|---|
| Alluvial rivers | |
| Bedrock river | |
| Bedforms | |
| Regional processes | |
| Mechanics | |
