Knowledge Organiser: Physical Geography Fieldwork (Rivers)
Part of Physical Geography Fieldwork · GCSE GCSE Geography revision
This topic summary covers Knowledge Organiser: Physical Geography Fieldwork (Rivers) within Physical Geography Fieldwork for GCSE Geography. Revise Physical Geography Fieldwork in Fieldwork for GCSE Geography with 0 exam-style questions and 20 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 16 of 16 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 16 of 16
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0 questions
Recall
20 flashcards
Knowledge Organiser: Physical Geography Fieldwork (Rivers)
Bradshaw Model Predictions
- Discharge: increases (more tributaries)
- Velocity: increases (less friction, wider channel)
- Width and depth: both increase (erosion)
- Pebble size: decreases (attrition)
- Pebble roundness: increases (attrition)
- Gradient: decreases (erosion to base level)
Data Collection Methods
- Velocity: float method (orange over 10 m) or flow meter
- Width: tape measure from bank to bank
- Depth: metre ruler at regular intervals across channel
- Pebble size: ruler, long axis in mm, 10–20 random pebbles
- Pebble roundness: Powers Roundness Scale (1–6)
- Gradient: clinometer and ranging poles
- Repeat each measurement 3× and take the mean
Sampling and Risk
- Sites: systematic (every 100–200 m downstream), 5–8 sites minimum
- Pebbles: random (reach in without looking)
- Key risks: slipping; deep/fast water; flash floods
- Control measures: non-slip footwear; buddy system; weather checks; never enter water above knee
- Spearman's rank: tests if correlation is statistically significant; critical value ±0.536 (n=14)
Evaluation Points
- Float only measures surface velocity (overestimates mean) — improve with flow meter
- One visit may not be typical — improve with repeat visits in different seasons
- Small pebble sample (10 per site) — improve by increasing to 20+
- Subjective roundness (Powers Scale) — improve by using one assessor throughout
- Too few sites (5) — improve by adding sites especially in middle course
- Reliability: consistency; Validity: measuring what you intend
Common Mistakes
- Not linking measurements to the Bradshaw Model: Every measurement must connect to a Bradshaw Model prediction — don't just record channel width; explain that you expect it to increase downstream as lateral erosion widens the channel
- Using the float method without acknowledging its limitation: The float measures surface velocity, which overestimates mean channel velocity — always state this limitation and suggest using a flow meter as an improvement
- Selecting pebbles by hand without randomising: Deliberately picking pebbles introduces bias — explain that you reached in without looking to ensure random selection and reduce the risk of choosing only accessible pebbles
- Weak Spearman's rank interpretation: Don't just state the r value — compare it to the critical value (±0.536 for n=14 at 95% confidence), state whether the correlation is statistically significant, and link the result back to your hypothesis
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