Rivers: Erosion, Transport & Hydrographs — GCSE Geography Revision

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What is Rivers: Erosion, Transport & Hydrographs?

River erosion involves four main processes: hydraulic action, abrasion, attrition, and solution. The eroded material, or load, is then transported downstream by traction, saltation, suspension, or solution. A hydrograph is a graph that shows how a river's discharge changes over time in response to a rainfall event. Key features include the rising limb, peak discharge, falling limb, and lag time, which is the delay between peak rainfall and peak discharge.

Board notes: Hydrograph interpretation is a key skill for all exam boards (AQA, Edexcel, OCR). Students are often asked to compare hydrographs for different river basins or to explain how human and physical factors can influence flood risk.

Worked example

Common mistakes

• 1Mixing up the four types of transportation. Traction is large boulders rolling, saltation is smaller pebbles bouncing, suspension is fine silt and clay being carried along, and solution is dissolved minerals.
• 2Misinterpreting hydrograph shapes. A 'flashy' hydrograph has a steep rising limb and short lag time, indicating a high flood risk, often due to impermeable surfaces or heavy rainfall. A 'subdued' hydrograph has a gentle rising limb and long lag time, suggesting a lower flood risk.
• 3Forgetting to label axes on hydrograph sketches. The y-axis should be labelled 'Discharge (cumecs)' and/or 'Rainfall (mm)', and the x-axis should be labelled 'Time (hours/days)'.

Rivers: Erosion, Transport & Hydrographs exam questions

Exam-style questions for Rivers: Erosion, Transport & Hydrographs with mark-scheme style solutions and timing practice. Aligned to AQA, Edexcel and OCR specifications.

Frequently asked questions

• What factors affect the shape of a hydrograph?

  Physical factors include basin size, slope, rock type (impermeable/permeable), and soil type. Human factors include urbanization (impermeable surfaces), deforestation (reduces interception), and the construction of dams and reservoirs.

• What is the difference between attrition and abrasion?

  Abrasion is when the river's load acts like sandpaper, scouring the bed and banks. Attrition is when the rocks being transported by the river collide with each other, becoming smaller and more rounded.