How does rejuvenation occur?
It occurs when there is either a fall in sea level relative to the level of the land or a rise of the land relative to the sea
This enables a river to renew its capacity to erode as its potential energy is increased
The river adjusts to its new base level - at first in its lower reaches and then progressivley inland
This can create a number of landforms: knickpoints, waterfalls and rapids, river terraces and incised meanders
What are knick points?
A sudden break or irregularity in the long profile of a river
Some are sharply defined such as waterfalls - others barely noticable
What is a river terrace?
A remnant of a fomer flooplain which has been abandoned at a higher level due to the renewed downcutting of a river
The terraces will cut back as the new valley is widened by lateral erosion
This process may be repeated several times leading to terraces at a number of different levels
Terraces provide useful shelter from floods and are ideal as natural routeways for road and rail
An example is near Kasbeki, Georgia
What are incised meanders?
There are 2 types: entrenched or ingrown
If a rejuvenated river occupies a valley with well developed meanders, renewed downcutting results in them becoming incised
If incision is rapid, the valley will be symmetrical with steep sides and a gorge like appearance - ENTRENCHED MEANDER
An example of an entrenched meander is in San Juan, southeastern Utah
When incision is slower and more lateral erosion is occuring - an INGROWN MEANDER may be produced. The valley becomes asymmetrical, with steep cliffs on the outer bends and more gentle slip-off slopes on the innner bends.
an example of an incised meander is on the River Wye, Tintern Abbey