Alluvial plain
An alluvial plain is a relatively flat and gently sloping earthform found at the base of a range of hills. As the hills erode due to weather and water flow the soil 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 solid material is deposited during flood conditions in the floodplain of the 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 meanders (a curving sinuous path). The leftover higher locations, typically natural levees at the margins of the flood channel, will themselves be weathered down from local erosion from 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.
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