Geography

1. 1.

   Fictional teaching dataset, not an observed basin: annual precipitation P = 900 mm, evapotranspiration E = 520 mm, runoff Q = 330 mm. Use P = E + Q + change in storage. After urbanisation, an equal storm produces a peak of 80 rather than 50 m³/s and a lag of 2 rather than 5 hours. Storm size is controlled; antecedent moisture is unknown. Distinguish infiltration from surface runoff and explain their effect on response time.

   [2 marks] · no calculator

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. Follow a raindrop along two routes. Entry into soil generally delays channel arrival relative to connected overland flow, though soil and slope conditions matter.
   2. Award each point once. Accept other well-supported interpretations addressing the task.

   Marking points

   • Infiltration enters soil and may feed slower subsurface pathways.
   • Surface runoff travels over land and can reach channels more rapidly.

   Examiner tip: Do not confuse infiltration into soil with percolation through it.

2. 2.

   Fictional teaching dataset, not an observed basin: annual precipitation P = 900 mm, evapotranspiration E = 520 mm, runoff Q = 330 mm. Use P = E + Q + change in storage. After urbanisation, an equal storm produces a peak of 80 rather than 50 m³/s and a lag of 2 rather than 5 hours. Storm size is controlled; antecedent moisture is unknown. Calculate annual change in storage and state whether storage rises or falls.

   [2 marks]

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. Rearrange the supplied balance to storage change = input minus the two outputs. The 50 mm is a depth equivalent across the basin, not a channel discharge.
   2. Award each point once. Accept other well-supported interpretations addressing the task.

   Marking points

   • Change in storage = 900 - 520 - 330 = +50 mm.
   • The positive balance means storage increases over the year.

   Examiner tip: Preserve the positive sign and the millimetre unit.

3. 3.

   Fictional teaching dataset, not an observed basin: annual precipitation P = 900 mm, evapotranspiration E = 520 mm, runoff Q = 330 mm. Use P = E + Q + change in storage. After urbanisation, an equal storm produces a peak of 80 rather than 50 m³/s and a lag of 2 rather than 5 hours. Storm size is controlled; antecedent moisture is unknown. Explain how urban surfaces can produce the changed peak and lag.

   [3 marks] · no calculator

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. Link the mechanism as a chain: less water enters storage, faster transfer concentrates arrival, and the river peak rises. The dataset is consistent with this chain but does not isolate every cause.
   2. Award each point once. Accept other well-supported interpretations addressing the task.

   Marking points

   • Impermeable surfaces reduce infiltration.
   • Drains connect runoff rapidly to the river, shortening lag.
   • More simultaneous arrival raises the peak discharge.

   Examiner tip: Give a process linking surface change to the hydrograph, not just 'urbanisation causes floods'.

4. 4.

   Fictional teaching dataset, not an observed basin: annual precipitation P = 900 mm, evapotranspiration E = 520 mm, runoff Q = 330 mm. Use P = E + Q + change in storage. After urbanisation, an equal storm produces a peak of 80 rather than 50 m³/s and a lag of 2 rather than 5 hours. Storm size is controlled; antecedent moisture is unknown. Explain why equal storm size does not make this a conclusive causal test.

   [3 marks] · no calculator

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. Controlling total rainfall removes one difference, not all differences. Compare intensity and wetness before interpreting the before/after contrast as an urbanisation effect.
   2. Award each point once. Accept other well-supported interpretations addressing the task.

   Marking points

   • Antecedent moisture affects remaining infiltration and storage capacity.
   • Storm intensity or spatial distribution may differ despite equal totals.
   • Repeated matched events would help separate land-use effects from these variables.

   Examiner tip: Control of one variable is not control of the whole catchment.

5. 5.

   Fictional teaching dataset, not an observed basin: annual precipitation P = 900 mm, evapotranspiration E = 520 mm, runoff Q = 330 mm. Use P = E + Q + change in storage. After urbanisation, an equal storm produces a peak of 80 rather than 50 m³/s and a lag of 2 rather than 5 hours. Storm size is controlled; antecedent moisture is unknown. Assess whether permeable paving alone is an adequate response to the raised peak.

   [4 marks] · no calculator

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. A local infiltration measure addresses one mechanism. Basin protection may also require detention, restored floodplain storage and limiting exposure; adequacy depends on how much runoff the paving actually intercepts.
   2. Award each point once. Accept other well-supported interpretations addressing the task.

   Marking points

   • Paving can restore infiltration and reduce connected runoff locally.
   • Benefits depend on soil permeability and maintenance of unclogged pores.
   • Coverage and intense rainfall may limit basin-scale peak reduction.
   • Recommends a justified combination or conditional use with storage and planning measures.

   Examiner tip: Judge scale and capacity, not merely whether a measure has some benefit.

6. 6.

   Fictional teaching dataset, not an observed basin: annual precipitation P = 900 mm, evapotranspiration E = 520 mm, runoff Q = 330 mm. Use P = E + Q + change in storage. After urbanisation, an equal storm produces a peak of 80 rather than 50 m³/s and a lag of 2 rather than 5 hours. Storm size is controlled; antecedent moisture is unknown. Design a before/after investigation to test a detention pond's effect on flood peaks.

   [4 marks] · no calculator

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. One small storm after construction cannot demonstrate success. Repeated event comparisons and a control help distinguish the pond from weather variation; automated sensors reduce exposure to hazardous flow.
   2. Award each point once. Accept other well-supported interpretations addressing the task.

   Marking points

   • Measures discharge at consistent locations and time intervals across multiple storms.
   • Records rainfall intensity and antecedent moisture to match comparable events.
   • Uses a suitable untreated comparison basin or reach to track wider changes.
   • Evaluates peak and lag with uncertainties and safe remote monitoring during floods.

   Examiner tip: Do not send students into a flooded channel to collect peak measurements.

Original, unofficial practice questions from SubjectScout — not official past-paper questions.