This document discusses river rejuvenation and the landforms it produces. River rejuvenation occurs when a river's base level changes, such as due to sea level change or glacial isostatic adjustment. This decreases the river's gradient, increasing its erosional power. Key landforms produced include waterfalls, incised meanders, river terraces, and knickpoints as the river grade is adjusted to the new base level.

1. River Rejuvenation
All your knowledge of rivers should
help you to understand this final
process which forms a unique set of
landforms.

2. Rejuvenate
To restore to a former
state; to make fresh or
new again

3. Learning Outcomes
• To understand how changes in base level
create different landforms.
• Explain the landforms produced by river
rejuvenation (15 marks)

4. Base Level
• Listen to the explanation of base level and
then produce a diagram to explain what it
is and how it changes.

5. Base Level
• Base level is the lowest level to which
erosion by running water can take place.

6. The River System
• River’s are always attempting to reach a
state of dynamic equilibrium where there
is a balance between the rate of erosion
and deposition.

7. Dynamic Rivers
• In reality a river is rarely, if ever, in a state
of dynamic equilibrium.
• Changes in discharge and sediment load
are constantly changing the profile of the
river.

8. For example….
• Waterfall
• Erosion near the waterfall
• Deposition lower downstream
• Lengthy period of heavy rain

9. Base Level changes
• Eustatic Change
– Changes to sea Level
• Isostatic change
– Glacial rebound

10. Changes
• Positive
Sea levels rise in
relation to the land.
The river loses
energy and as such
deposition dominates
and coastal areas
flood.
• Negative
Sea levels fall in
relation to the sea.
Land emerges from
the sea, steepening
the river gradient thus
increasing the rivers
erosional power.

11. Base Level
• Produce your diagram

12. Key Points
• Rivers begin to regrade from the point
nearest the sea.
• It often happens again before a river has
reached dynamic equilibrium giving it a
partly graded profile.
• Knickpoints
• Incised meanders
Changes to the cross
• River terraces
profile of the river
• Waterfalls

13. River in grade
Flood plain

14. Waterfall
retreats
cutting
a lower valley
Fall in sea level
River bluffs
New flood plain forms

15. River bluffs
New flood plain forms
Waterfall
decreases in size
to form rapids
(knick point)
River Terrace

16. Terraces

17. Knickpoints and waterfalls

20. Incised Meanders

25. • The likely story is that the streams once
flowed across nearly flat lowlands.
• Then, uplift of the rocks began, giving the
streams a steeper slope to the sea and so
speeding their flow and causing them to
erode.
• But, the uplift was gradual enough that the
streams held their old courses.
• The streams cut downward without a
change in pattern, which is called incision.

26. Write three level descriptors for this
question
Explain the landforms produced by river
rejuvenation (15 marks)
Level 1 : BASIC
Level 2 : CLEAR
Level 3 : DETAILED

27. Review
BASE LEVEL
INCISION
ISOSTATIC UPLIFT
KNICK POINT