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In this lesson we are going to discuss what river rejuvenation is and ways in which it occurs

Answer Text:
River Rejuvenation
- Renewal of erosive activity of a river.
- Happens in the old stage.
Causes
A. Change in the Base Level
Base level is the lowest level to which a river can erode its bed.
Rejuvenation resulting is called dynamic rejuvenation
1. Drop in sea level
- The river mouth moves further seawards.
- A steep gradient occurs between the old and the new mouths causing the river to starts to move swiftly.
- Vertical erosion resumes extending back to the flood plain.
2. Uplift of a section of land along the rivers course.
- Faulting or folding may occur.
- A section of land along a rivers course is uplifted.
- The gradient is increased causing the river to flow swiftly and undercut through the uplifted section.
- An antecedent gorge is formed.
3. Unequal sinking of land along a rivers course.
- The downstream side sinks more than the upstream one.
- An increase ingredient occurs causing the river to flow swiftly
- The river starts to undercut more vigorously than before.
B. Increase in Rivers Discharge
Rejuvenation resulting is called static rejuvenation
- The rivers discharge increases due to high precipitation or capture.
- The rate of erosion becomes higher due to increased discharge.
- The river starts to undercut more vigorously.
C. Change in Rock Structure
- A river passes a resistant rock and starts flowing over a less resistant rock.
- The river starts eroding more vigorously into the softer rocks.
Features of River
Rejuvenation
1. Knick Points
- A sudden break of slope in a rivers profile as a result of change in sea level.

2. River Terraces
- Step like features formed when a river rejuvenates and cuts a new valley through the flood plain causing a platform will form where the floor of the
former flood plain was.
3. Water Falls
- Are formed when knick points are deepened e.g. Charlotte falls in Sierra Leone.
4. Antecedent Gorges
- Gorges which form where a river undercuts though a section of land that is being uplifted e.g. Turkwel gorge.
5. Incised Meanders
- Meanders that have been cut deeper into by a rejuvenated river.
Types
a) Entrenched Meanders

- Formed from vertical erosion causing both valleys to be steep and symmetrical.
b) Ingrown Meanders
- Formed by lateral and vertical erosion causing one valley side to be steeper than the other and hence asymmetrical in cross section.

6. Abandoned Meanders

- Meanders abandoned during formation of oxbow lakes when the river takes a short-cut leaving an enclosed portion of
land surrounded by an oxbow lake.