Lecture Notes: Upper Course of the River Severn - GCSE Case Study

Introduction

• Location: Upper course of the River Severn
• Focus: Understanding river processes in the upper course as part of the GCSE case study.

Characteristics of the Upper Course

• Relief:
  • High relief areas typically found in mountains.
  • Water flows at a surprisingly slower speed despite the steep gradient.

Formation of Waterfalls

• Conditions:

  • Waterfalls typically form in the upper course due to steep gradients.
  • Presence of hard rock followed by soft rock.

• Erosional Processes:

  • Hydraulic Action:
    • Water flows into cracks in the softer rock, creating pressure and causing erosion.
    • Leads to formation of waterfalls as water moves over and into softer rock.
  • Abrasion:
    • River transports pebbles which abrade, or rub away, at softer rock.

• Development of Waterfalls:

  • Soft rock is eroded, forming an overhang above the plunge pool.
  • Continued erosion enlarges the overhang.
  • Over time, gravity causes the overhang to collapse into the plunge pool.
  • As this process repeats, the waterfall retreats backward, creating a gorge.

Case Study Example

• Glenn Hetherin Waterfall:
  • Demonstration of the gorge formation process where the waterfall retreats.

Recap: Four-Stage Process of Gorge Formation

1. Hard rock followed by soft rock.
2. Soft rock eroded by hydraulic action and abrasion.
3. Formation of an overhang that eventually collapses.
4. Creation of a gorge as the waterfall continues to retreat.

Conclusion

• The lecture will continue with the middle course of the river in subsequent sessions.
• Additional notes on another topic (e.g., "great chocolate") mentioned for a future discussion.