What is river rejuvenation?
It occurs when a river changes from being in equilibrium with its landscape to being dominated by erosion.
It happens when:
- there is an increase in discharge
- there is a change in base level
Sea level changes due to:
Isostatic changes: local changes were the height of the land changes relative to the global sea level
Eustatic changes: global change in sea level
If sea level falls, the river has a steeper gradient and adjusts by cutting down to the new base level.
Where the new graded profile intersects the old, an abrupt change of gradient develops.
Rapidly occuring renewed erosion causes a river to incise its channel into its floodplain.
This creates abandoned terraces of remnants of the original floodplain.
They occur when a rejuvenated river cutes vertically through its floodplain and into solid bedrock.
Intrenched meanders: rapid downcutting, little erosion
Ingrown meanders: slower rate of downcutting, valley slope decline is significant
Tectonic uplift may accelerate the process of incision.