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 slight slope.

The Glossary of Landform and Geologic Terms, maintained by the United States National Cooperative Soil Survey (NCSS), defines an "alluvial plain" as "a large assemblage of fluvial landforms (braided streams, terraces, etc.) that form