S5 Geography Practice Paper: River Processes, Coastal Landforms, Weather, Plate Tectonics and Map Skills
- 2026-11-12
S5 geography practice paper: river discharge, coastal erosion, lapse rate and humidity, plate motion and earthquake energy, catchment runoff and map scale.
Part 1: River discharge and channel characteristics (20 marks)
A river reach is 24 m wide with a mean depth of 2.5 m and a mean velocity of 1.2 m per second. Over the 8 km upstream of the reach the bed falls 12 m. The channel itself measures 11.2 km long, while the valley it occupies is 8.0 km long.
| # | Question | Answer and marking notes |
|---|---|---|
| 1 | Calculate the cross-sectional area and the discharge of the reach. | Answer: Area = 24 x 2.5 = 60.0 square metres; discharge = 60.0 x 1.2 = 72.0 cubic metres per second. |
| 2 | Estimate the hydraulic radius, taking wetted perimeter as width plus twice the mean depth. | Answer: Wetted perimeter = 24 + 2 x 2.5 = 29.0 m; hydraulic radius = 60.0 / 29.0 = 2.07 m. A larger hydraulic radius means less frictional resistance. |
| 3 | Calculate the channel gradient and express it in the form 1 : N. | Answer: Gradient = 12 / 8,000 = 0.0015, that is 1 : 667. |
| 4 | Calculate the sinuosity and describe the channel form. | Answer: Sinuosity = 11.2 / 8.0 = 1.4. Above 1.3 the channel is meandering, with slower flow, deposition on the inner bank and erosion on the outer bank. |
Part 2: Coastal erosion and longshore drift (20 marks)
A sea cliff is 35 m high and loses 42 cubic metres of rock per metre of coast each year. Mean wave height there rises from 1.5 m to 3.0 m. Longshore drift moves 45,000 cubic metres of sand past a section each year, and the beach is 5 km long and 30 m wide. Sediment input to the coast is 62,000 cubic metres a year against an output of 78,500 cubic metres.
| # | Question | Answer and marking notes |
|---|---|---|
| 5 | Calculate the annual retreat of the cliff. | Answer: Retreat = 42 / 35 = 1.2 m per year. For the same volume lost, a lower cliff retreats faster. |
| 6 | Wave energy is proportional to the square of wave height. If height rises from 1.5 m to 3.0 m, by what factor does energy increase? | Answer: Height ratio = 3.0 / 1.5 = 2; energy ratio = 2 squared = 4.0 times. Winter swell can therefore multiply erosive power. |
| 7 | Assuming all drifted sand stays on the beach, calculate the average annual thickening of the sand layer. | Answer: Beach area = 5,000 x 30 = 150,000 square metres; thickening = 45,000 / 150,000 = 0.3 m per year. |
| 8 | Calculate the annual sediment budget and state the coastal trend. | Answer: Net change = 62,000 – 78,500 = -16,500 cubic metres. Output exceeds input, so the beach is narrowing and erosion dominates. |
Part 3: Lapse rate and atmospheric humidity (20 marks)
Sea-level temperature is 28.4 degrees C and the lapse rate is 6.5 degrees C per km. At a station at 20 degrees C the actual vapour pressure is 16.8 hPa and the saturation vapour pressure at that temperature is 23.4 hPa. Saturation values are 16.0 hPa at 14 degrees C and 17.1 hPa at 15 degrees C. Annual rainfall at the foot of the windward slope is 1,180 mm; the air then rises a further 500 m, giving 22 mm per 100 m. Leeward rainfall is 72 per cent of the windward total.
| # | Question | Answer and marking notes |
|---|---|---|
| 9 | Calculate the temperature at the top of a 1,600 m peak. | Answer: Lapse = 6.5 x 1.6 = 10.4 degrees C; summit temperature = 28.4 – 10.4 = 18.0 degrees C. |
| 10 | Calculate the relative humidity at the station. | Answer: Relative humidity = 16.8 / 23.4 = 71.8 per cent. The air is unsaturated and can still take up more water vapour. |
| 11 | Use the saturation values given to estimate the dew point. | Answer: The actual vapour pressure of 16.8 hPa lies between 16.0 at 14 degrees C and 17.1 at 15 degrees C, so the dew point is about 14.7 degrees C, close to saturation. |
| 12 | Calculate the annual rainfall on the leeward slope. | Answer: Windward total = 1,180 + 5 x 22 = 1,290 mm; leeward = 1,290 x 72 per cent = 928.8 mm, giving a rain shadow. |
Part 4: Plate motion and earthquake energy (16 marks)
A plate moves 6.5 cm a year for 2.4 million years. One earthquake measured 5.2 and another 7.2; each unit of magnitude multiplies energy by about 31.6. P waves travel at 6.0 km per second and S waves at 3.5 km per second, and the epicentral distance is 84 km. Earthquake energy can be estimated from log E = 4.8 + 1.5 M, with E in joules.
| # | Question | Answer and marking notes |
|---|---|---|
| 13 | Calculate how far the plate moves in 2.4 million years, in km. | Answer: 6.5 x 2,400,000 = 15,600,000 cm = 156,000 m = 156 km. |
| 14 | Calculate how many times more energy a magnitude 7.2 event releases than a 5.2 event. | Answer: Magnitude difference = 2.0; energy ratio = 31.6 squared which is about 1,000 times, that is roughly one thousand. |
| 15 | Calculate the difference in arrival time between the P and S waves. | Answer: P wave = 84 / 6.0 = 14.0 s; S wave = 84 / 3.5 = 24.0 s; difference = 10.0 s. A larger gap means a more distant epicentre. |
| 16 | Use the formula to estimate the energy released by a magnitude 6.0 earthquake. | Answer: log E = 4.8 + 1.5 x 6.0 = 13.8; E is about 6.3 x 10^13 joules, comparable to roughly 15,000 tonnes of TNT. |
Part 5: Catchment runoff and water resources (12 marks)
A catchment covers 48 square km. A storm delivers 165 mm of rain and the runoff coefficient is 0.35. The reservoir can capture 60 per cent of the runoff, and daily supply is 180,000 cubic metres.
| # | Question | Answer and marking notes |
|---|---|---|
| 17 | Calculate the total volume of rain falling on the catchment. | Answer: 48 x 165 x 1,000 = 7,920,000 cubic metres. One square km receiving 1 mm of rain gains 1,000 cubic metres. |
| 18 | Calculate the runoff generated by the storm. | Answer: 7,920,000 x 0.35 = 2,772,000 cubic metres. |
| 19 | Calculate the combined volume lost to evaporation, infiltration and groundwater recharge. | Answer: 7,920,000 x 0.65 = 5,148,000 cubic metres. |
| 20 | Calculate the volume the reservoir can capture and how many days of supply it supports. | Answer: Captured = 2,772,000 x 0.60 = 1,663,200 cubic metres; days = 1,663,200 / 180,000 which is about 9.2 days, under a fortnight. |
Part 6: Map scale, gradient and area (12 marks)
A map has a scale of 1 : 20,000. Two points lie 6.4 cm apart on the map. The horizontal distance between the 120 m and 240 m contours on the map is 1.2 km. A rectangular area measures 5 cm by 4 cm on the map. A walking route is 4.8 km long and walking speed is 4 km per hour.
| # | Question | Answer and marking notes |
|---|---|---|
| 21 | Calculate the real distance between the two points. | Answer: 6.4 x 20,000 = 128,000 cm = 1,280 m = 1.28 km. |
| 22 | Calculate the slope percentage of that hillside. | Answer: Height difference = 240 – 120 = 120.0 m; horizontal distance = 1,200 m; slope = 120.0 / 1,200 = 10.0 per cent. |
| 23 | Calculate the real area of the rectangular region. | Answer: 1 cm represents 200 m, so 1 square cm represents 40,000 square metres; 20 x 40,000 = 800,000 square metres, that is 0.8 square km. |
| 24 | Calculate the time needed to walk the whole route. | Answer: 4.8 / 4 = 1.2 hours, that is 72 minutes. Add rest time for uphill sections. |
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