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S4 Geography: River Landforms – Challenge Practice (10 Questions)
S4 Geography: River Landforms – Challenge Practice (10 Questions)
Ten harder items cover flood plains, graded profiles, waterfall retreat, sediment yield, return-period probability, point bars, terraces, delta classification and urban hydrology.
Quick answer 1. fine alluvium left by floods; 2. a smooth concave-up curve; 3. 150 m; 4. 1 095 000 tonnes; 5. about 9.6 per cent; 6. point bar of sand and gravel; 7. renewed downcutting strands the old flood plain; 8. balance of supply against waves and tides; 9. higher peak, shorter lag; 10. armouring only slows erosion.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | about 30 minutes |
| Difficulty mix | Foundation 2 · Intermediate 2 · Challenge 5 · Error redo 1 |
| Chapter | Chapter: S4 Geography | River Landforms: erosion, transport, deposition and valley development |
| Level | S4 |
02 Questions (10 items)
- FoundationWhat is a flood plain?
- FoundationWhat shape does a river long profile normally take?
- IntermediateA waterfall retreats 1.5 m a year. How far has it retreated in 100 years?
- IntermediateA river carries 3 000 tonnes of suspended load a day. What is the annual total over 365 days?
- ChallengeA flood has a 100-year return period. What is the chance of at least one such flood in the next 10 years?
- ChallengeWhat depositional feature builds on the inside of a meander bend, and of what is it made?
- ChallengeHow does a river terrace form?
- ChallengeWhat mainly controls the shape of a delta?
- ChallengeHow do peak discharge and lag time change after urbanisation?
- Error redoA student says an armoured bed means the river has stopped eroding. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | The flat lowland built of fine alluvium laid down when a river overtops its banks. | Each flood leaves a thin sheet of silt, and the layers build into a flat fertile plain. |
| 2 | A smooth concave-up curve, steep near the source and gentle near the mouth. | The graded profile is the ideal form reached when erosion and deposition balance. |
| 3 | 150 m. | The fall retreats because soft rock beneath is hollowed out and the hard cap collapses. |
| 4 | 1 095 000 tonnes. | Suspended load usually dominates total load, though the share varies with basin geology. |
| 5 | About 9.6 per cent, from 1 minus 0.99 to the power 10. | A 100-year event has a 1 per cent annual exceedance probability, not one guaranteed hit every century. |
| 6 | A point bar, built of coarser sand and gravel. | The slow inner bend drops the coarser load first, building a shoal that slopes toward the channel. |
| 7 | The river renews its downcutting and leaves an old flood plain standing as a bench above the new level. | Uplift or a larger discharge makes the river cut down again, stranding the former flood plain on the valley side. |
| 8 | The balance between river sediment supply and the destructive power of waves and tides. | River-dominated deltas prostrate, wave-dominated ones are smoothed, and tide-dominated ones are cut into funnels. |
| 9 | The peak becomes higher and arrives sooner, so lag time shortens. | Impermeable surfaces cut infiltration, and rain reaches the channel quickly, giving a flashier flood. |
| 10 | Armouring only shields the bed with a coarse surface layer, so erosion continues but more slowly. | Fine grains are winnowed away and a gravel lag remains, which needs a higher velocity to move. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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