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river





river transport and deposition
Process of change at work within a river. The material of the river-bed is being continually worn away, and transported and deposited elsewhere; how much and how far depends on the river's speed and turbulence. The movement of eroded material is indicated by arrows. (1) Straight river with symmetrical bed; the eroded material is deposited on the banks when the water level is high. (2) Winding river with an asymmetrical bed; material is worn off the concave bank, usually the outer side of a curve, and deposited on the convex.

A body of inland water that flows in a natural channel into the sea, a lake, or, as a tributary, into another river. The main sources of rivers are springs, lakes, and glaciers. Near the source a river flows swiftly, the rocks and other abrasive particles eroding a steep-sided V-shaped valley (see erosion). Variations in the hardness of the rocks over which it runs may result in waterfalls. In the middle part of its course the gradients become less steep, and lateral (sideways) erosion becomes more important than downcutting. The valley is broader, the flow less swift, and meandering more common. Toward the river mouth, the flow becomes more sluggish and meandering prominent: the river may form oxbow lakes. Sediment may be deposited to form a delta.


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