GEO • SHS 1Term 2WAEC / WASSCE SyllabusVIP Lesson
Action of Running Water & River Basin Development
Stages of a river (upper, middle, lower course), river erosion, transportation, deposition features, and the drainage system of Ghana.
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Real-World Context & Relevance in Ghana
Akosombo Dam harnessed the gorge of the lower Volta River to create the largest man-made lake by surface area, generating hydro-electricity.
Key Syllabus Learning Objectives
- 1Examine the four processes of river erosion and transportation
- 2Identify characteristic landforms formed in the upper, middle, and lower courses of a river
- 3Describe the main drainage basins of Ghana and the economic importance of the Volta Lake
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Comprehensive Syllabus Study Notes
• River Work (Erosion, Transportation, Deposition):
- Three Erosional Mechanisms: Hydraulic action (sheer water force), Corrasion/Abrasion (rock debris scouring bed), Attrition (pebbles colliding and rounding), Corrosion/Solution.
- Four Transport Modes: Traction (rolling large boulders), Saltation (bouncing pebbles), Suspension (floating silt/clay), Solution (dissolved minerals).
• The Three River Courses:
- Upper / Torrent Course: Steep gradient, dominant vertical erosion, V-shaped valleys, gorges, waterfalls, rapids, river capture.
- Middle / Valley Course: Moderate gradient, lateral erosion begins, U-shaped valley, interlocking spurs, meanders.
- Lower / Plain Course: Gentle gradient, dominant deposition, wide floodplains, oxbow lakes, braided streams, levees, deltas, and estuaries.
• Ghana's Drainage Basin: Dominated by the Volta River system (Black Volta, White Volta, Oti, Afram) and coastal rivers (Pra, Ankobra, Tano, Densu).
- River Work (Erosion, Transportation, Deposition):
- Three Erosional Mechanisms: Hydraulic action (sheer water force), Corrasion/Abrasion (rock debris scouring bed), Attrition (pebbles colliding and rounding), Corrosion/Solution.
- Four Transport Modes: Traction (rolling large boulders), Saltation (bouncing pebbles), Suspension (floating silt/clay), Solution (dissolved minerals).
- The Three River Courses:
- Upper / Torrent Course: Steep gradient, dominant vertical erosion, V-shaped valleys, gorges, waterfalls, rapids, river capture.
- Middle / Valley Course: Moderate gradient, lateral erosion begins, U-shaped valley, interlocking spurs, meanders.
- Lower / Plain Course: Gentle gradient, dominant deposition, wide floodplains, oxbow lakes, braided streams, levees, deltas, and estuaries.
- Ghana's Drainage Basin: Dominated by the Volta River system (Black Volta, White Volta, Oti, Afram) and coastal rivers (Pra, Ankobra, Tano, Densu).
Practical Example:
Akosombo Dam harnessed the gorge of the lower Volta River to create the largest man-made lake by surface area, generating hydro-electricity.
Core Takeaway:
In diagram questions, draw the horseshoe cutoff loop clearly when illustrating the formation of an ox-bow lake.
WAEC / WASSCE Examiner Tips
- In diagram questions, draw the horseshoe cutoff loop clearly when illustrating the formation of an ox-bow lake.
Common Candidate Pitfalls & Errors to Avoid
- Reporting discharge as width times velocity, forgetting the depth that makes the cross-sectional area.
- Confusing the vertical drop of a river with its gradient, which is drop divided by distance.
- Placing gorges and waterfalls in the lower course and deltas in the upper course of the same river.
- Describing a flood hydrograph as a rainfall graph, so lag time and peak discharge are never identified.
- Naming a dam's benefits only in power terms and ignoring irrigation, navigation, fishing and flood control.
Topic Mastery Checklist
- Examine the four processes of river erosion and transportation
- Identify characteristic landforms formed in the upper, middle, and lower courses of a river
- Describe the main drainage basins of Ghana and the economic importance of the Volta Lake
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