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Learning Objectives:

River Rejuvenation. Specification Focus: GEOG1 – Process and impact of rejuvenation – knick points, waterfalls, river terraces and incised meanders. Learning Objectives: To understand the process of rejuvenation in rivers and the landforms associated with this.

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Learning Objectives:

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  1. River Rejuvenation Specification Focus: GEOG1 – Process and impact of rejuvenation – knick points, waterfalls, river terraces and incised meanders. • Learning Objectives: • To understand the process of rejuvenation in rivers and the landforms associated with this. • To practice map skills using an OS map • To practice exam technique on a past paper question

  2. River Rejuvenation

  3. Causes of Rejuvenation There are two causes of rejuvenation in rivers: 1) Eustatic Rejuvenation  Caused by sea-level change related to the amount of water in the oceans. 2) Isostatic Change  Caused by sea-level change related to rise and fall of the land. These processes give the river more potential energy and thus a greater capacity to __________________________.

  4. If sea level falls (or land rises) the river adjusts to its new base level, firstly in the lower reaches, and then progressively inland. River retreats cutting a lower valley Fall in sea level

  5. If sea level falls (or land rises) the river adjusts to its new base level, firstly in the lower reaches, and then progressively inland. River Bluffs New floodplain forms

  6. River Rejuvenation

  7. Knickpoints • A sudden break or irregularity in the gradient of the long profile • Usually marked by rapids but may be sharply defined as a waterfall

  8. Knickpoint

  9. River Terraces River terraces are remnants of old river floodplains left at higher levels after a river down cuts due to rejuvenation Several terraces may be left if rejuvenation occurs more than once http://www.bbc.co.uk/learningzone/clips/river-terraces/402.html

  10. River Terraces Large and small scale river terraces

  11. Incised Meanders • These are formed when a river cuts down into its bed and deepens it’s meanders. There are 2 types of incised meander: Ingrown Entrenched

  12. Entrenched Meanders

  13. Ingrown Meanders

  14. Another cause: River capture  All rivers tend to cut back towards their source by headward erosion. Sometimes the river may cut into an adjacent river valley and join up with the tributaries of another river.

  15. Case Study the River Rheidol, Ceredigion

  16. Case Study the River Rheidol, Ceredigion

  17. Case Study the River Rheidol, Ceredigion

  18. Case Study the River Rheidol, Ceredigion

  19. Case Study the River Rheidol, Ceredigion TASK Practice your cartographic skills by completing the worksheet on the River Rheidol QUESTION What is the symbol for a rock outcrop and a cliff on an OS map? EXTENSION: Locate grid square 7579. This is an excellent example of an incised meander. Draw an enlarged version of this grid square to show the main features of the meander. Mark on some contours to indicate how the meander has become a winding gorge. Add labels to describe the main features.

  20. What could I be asked in the EXAM? • Describe and explain the formation of channel features that can be created by the process of river rejuvenation (15 marks) • Start off by writing a short plan of how you would answer the question. You can do this as a mind map or bullet points. • Then try writing out your answer in full. It should take you no longer that 15 minutes. • Once you’ve finished, swap your answer with someone else and use the mark scheme to give them a mark. Also give them 2 comments: •  what they have done well •  what they could do to improve

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