GEO 110 Lecture Notes - Lecture 10: Downcutting, Alluvium, Bed Load
4 Feb 2020
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Document Summary
Stream carry their loads downslope toward a valley, a. Whenever a stream"s load exceeds its capacity , it deposits some of its load , alluvium. Typically occurs where the velocity of streamflow decreases. Stream develops a graded profile in which the gradient is just sufficient to carry the average annual load of water and sediment produced by its drainage basin. Stream develops a more-or-less stable state, in which its long-term capacity to transport sediment is matched by the long-term rate at which it receives sediment, known as a graded stream. Stream becomes graded and begins to build a floodplain. River moves freely from one side of the valley to the other. Where rapid uplift causes meandering rivers to cut deeply into bedrock, entrenched meanders are formed. Alluvial terraces form when an aggrading river loses its sediment input and begins degrading its bed, leaving terraces behind as it cut deeper into its sediment-filled valley.
