Alluvial fans, formed where a sediment-laden stream emerges from a confined valley onto a flatter plain (causing an abrupt decrease in flow competence and gradient), are characterized by two dominant processes: braiding (multiple shifting shallow channels due to high sediment load exceeding transport capacity) and avulsion (sudden abandonment of the active channel course in favor of a new path across the fan surface, often triggered by channel aggradation and blockage).
As a stream exits a mountain front onto an alluvial fan, the sudden loss of confinement and reduced gradient causes rapid deposition and channel bed...
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