Entrenched river

An entrenched river refers to a river that is confined to a canyon or gorge, and in most cases, it is relatively narrow with very little or no flood plain. It often has meanders already developed into landscapes. An entrenched river usually forms a rapid downcutting of the river channel before it changes its course. The river downcutting may occur rapidly as a result of a tectonic uplift rift or when a lowering of the ocean floor takes place. Increased level of downcutting is also possible when a moraine-dammed lake collapses downstream, or when there is a capture of a river by another river. The meanders formed in these landscapes refer to incised meanders and they occur in two forms, including an ingrown meander and entrenched meander. An ingrown meander occurs when downcutting process is slow and the river can cause lateral erosion, leading to an asymmetric valley. The feature developed when such processes occur refers to un-incised meander. On the other hand, entrenched meander occurs when there is a rapid incision of the river bed such that the river does not have the opportunity to erode the lateral side. This leads to symmetrical valleys with a gorge-like appearance. It is widely believed that the development of these two features occurs before the rejuvenation does.

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