Entrenched river

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An entrenched river is a river that is confined to a canyon or gorge, usually with a relatively narrow width and little or no flood plain, and often with meanders worn into the landscape. Such rivers form when an area is elevated rapidly or for some other reason the base level of erosion is rapidly lowered, so that the river begins downcutting into its channel faster than it can change course (which rivers normally do on a constant basis). If the river had pronounced meanders before the lowering of the base level of erosion, then those meanders may be "carved into stone", as it were. An example of entrenched meanders may be seen in the Snake River Canyon in southern Idaho.