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S4 Geography Practice Paper: River Processes, Urbanisation and Land Use (12 questions, 100 marks, 75 minutes)
S4 Geography: River Processes, Urbanisation and Land Use
S4 geography paper: river discharge, catchment runoff, return periods, channel gradient, city growth, land-use change and delta sedimentation. 12 questions, 100 marks, full answers.
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Paper details Level: S4 | Subject: Geography | Time: 75 minutes | Marks: 100 | Questions: 12 | Answers included
Section A: Short Questions (25 marks)
Answer all questions and show your working.
| # | Question | Answer and marking notes |
|---|---|---|
| 1 | A river channel is 12 m wide with a mean depth of 1.5 m and a mean velocity of 0.8 m/s. (a) Find the discharge. (b) If the discharge doubles while the cross-section area stays the same, find the new mean velocity. | Area = 12 x 1.5 = 18 m2; discharge = 18 x 0.8 = 14.4 m3/s. Doubled discharge = 28.8 m3/s, so velocity = 28.8 / 18 = 1.6 m/s. Marks: (a) 3; (b) 3. |
| 2 | A catchment of 48 km2 receives 2,400 mm of rain a year and has a runoff coefficient of 0.35. (a) Find the volume of rain falling on the catchment per year in m3. (b) Find the annual runoff volume in m3. | 48 km2 = 48000000 m2; 2,400 mm = 2.4 m. Rain volume = 48000000 x 2.4 = 1.152e+08 m3. Runoff = 1.152e+08 x 0.35 = 4.032e+07 m3. Marks: 3 + 3. |
| 3 | A gauging station recorded 3 flood events above the warning level in 30 years. (a) Find the return period. (b) Find the probability of exceedance in any one year. (c) Find the probability of at least one exceedance in the next 5 years (3 decimal places). | (a) Return period = 30 / 3 = 10 years. (b) P = 1/10 = 0.10. (c) 1 – (1 – 0.10)^5 = 0.410. Marks: 2 + 2 + 3. |
| 4 | A river falls from 800 m at its source to sea level, with a channel length of 200 km. Find the average gradient and express it as a percentage. | Gradient = 800 / 200000 = 0.0040 = 0.4%. Marks: formula 3, conversion 2, unit 1. |
Section B: Urbanisation and Land Use (30 marks)
State the formula used and give percentages to 3 significant figures.
| # | Question | Answer and marking notes |
|---|---|---|
| 5 | A city population grew from 2.4 million in 2010 to 3.6 million in 2020. (a) Find the total growth over the ten years. (b) Find the annual compound growth rate (3 significant figures). | (a) Growth = (3.6 – 2.4)/2.4 = 50%. (b) CAGR = 1.5^(1/10) – 1 = 4.14%. Marks: 4 + 4. |
| 6 | A city covers 180 km2 with 3.6 million people; ten years later it covers 240 km2 with 4.08 million people. Find the population density in both periods and state the direction of change. | Initial: 3,600,000 / 180 = 20000 per km2; later: 4,080,000 / 240 = 17000 per km2. Density falls by 3000 per km2 because the built area expanded faster than the population. Marks: 3 + 3 + 1. |
| 7 | Land use in a basin: in 1990 farmland 62%, built-up 18%, woodland 20%; in 2020 farmland 38%, built-up 42%, woodland 20%. (a) Find the fall in farmland in percentage points. (b) Find the percentage increase in built-up land. | (a) Farmland falls from 62% to 38%: a drop of 24 percentage points. (b) Built-up rises from 18% to 42%: 133.3% increase. Marks: 4 + 4. |
| 8 | Site scores for a factory (out of 10): transport A 8 / B 6, labour A 6 / B 9, land A 5 / B 7, market A 7 / B 6, with weights 0.4, 0.3, 0.2 and 0.1. Find the weighted totals and recommend a site. | A: 0.4×8 + 0.3×6 + 0.2×5 + 0.1×7 = 6.7; B: 0.4×6 + 0.3×9 + 0.2×7 + 0.1×6 = 7.1. B scores higher, so site B is recommended; its weaker transport access should be noted. Marks: 6 + 1. |
Section C: Long Questions (45 marks)
Answer in full steps or with a table.
| # | Question | Answer and marking notes |
|---|---|---|
| 9 | A flood storage pond is 40,000 m2 in area and 3 m deep. During a 2-hour storm the excess flow above the downstream capacity is 15 m3 per second. (a) Find the pond capacity. (b) Find the volume that must be stored. (c) Decide whether the capacity is sufficient and give the spare capacity. | (a) Capacity = 40,000 x 3 = 120000 m3. (b) Storage needed = 15 x 3,600 x 2 = 108000 m3. (c) 120000 > 108000, so capacity is sufficient with 12000 m3 spare. Marks: 4 + 4 + 4. |
| 10 | A basin has a bifurcation ratio of 4 and 64 first-order streams. (a) Find the number of second-, third- and fourth-order streams. (b) Find the total number of streams of orders 1 to 3. (c) Explain the link between stream order and basin area. | (a) Order 2: 64/4 = 16; order 3: 4; order 4: 1. (b) Orders 1 to 3 total 84. (c) Higher order means a larger basin area, with order 4 draining the whole basin. Marks: 3 + 3 + 2 + 3. |
| 11 | A delta covers 40 km2 and receives 5 mm of sediment a year at a density of 1,600 kg/m3. The river carries 3.2 million tonnes of sediment a year. (a) Find the annual sediment volume. (b) Find the annual deposited mass in million tonnes. (c) Find the deposition efficiency as a percentage of load. | (a) Volume = 40e6 x 0.005 = 200000 m3. (b) Mass = 200000 x 1,600 / 1,000 = 320000 tonnes = 0.32 million tonnes. (c) Efficiency = 0.32 / 3.2 = 10%. Marks: 4 + 4 + 4. |
| 12 | A city of 3.6 million people uses 220 L of water per person per day. (a) Find the total daily water use in m3. (b) If 15% of demand is met by reclaimed water, find the daily saving. | (a) Daily use = 220 x 3,600,000 / 1,000 = 792000 m3. (b) Saving = 792000 x 0.15 = 118800 m3 per day. Marks: 5 + 5. |
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