River Rejuvenation AQA

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

KNICKPOINTS:

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.

RIVER TERRACES:

Rapidly occuring renewed erosion causes a river to incise its channel into its floodplain.

This creates abandoned terraces of remnants of the original floodplain.

INCISED MEANDERS:

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.