Physical Geography Fieldwork Investigation

For AQA GCSE Geography, you must complete at least one fieldwork investigation in a physical geography environment. Common topics include river studies, coastal investigations, weather measurement, and ecosystem surveys. This lesson provides detailed guidance on planning and conducting a physical geography fieldwork investigation, with a focus on the most popular choice — a river study.

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Choosing a Physical Fieldwork Topic

Common physical fieldwork investigations include:

Topic	Example Question
River channel changes	"How do channel characteristics change downstream?"
Coastal processes	"How does longshore drift affect beach profiles at different locations?"
Weather and microclimate	"How does temperature and wind speed vary across an urban-rural transect?"
Ecosystems	"How does vegetation cover change across a sand dune succession?"

The most popular — and the one we will focus on in detail here — is the river channel study based on the Bradshaw model.

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The Bradshaw Model

The Bradshaw model predicts how river characteristics change from source to mouth (upstream to downstream):

Variable	Upstream	Downstream
Channel width	Narrow	Wide
Channel depth	Shallow	Deep
Velocity	Slow (often)	Fast
Discharge	Low	High
Gradient (slope)	Steep	Gentle
Bedload size	Large	Small
Bedload shape	Angular	Rounded

Exam Tip: The Bradshaw model is the theoretical framework you should use to develop your hypothesis. For example: "Channel width will increase downstream because tributaries add water, increasing discharge."

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Developing a Hypothesis

Your hypothesis must be:

• Specific — state which variable(s) you are testing
• Directional — state the expected direction of change
• Linked to theory — explain why you expect this change

Examples:

• "Channel width will increase from upstream to downstream along the River X, consistent with the Bradshaw model"
• "Bedload size will decrease downstream due to erosion processes (attrition and abrasion) reducing pebble size"

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Choosing Study Sites

Select sites along the river course, from near the source to near the mouth (or as far downstream as is safe and accessible).

Site Selection Criteria

• Systematic sampling: choose sites at regular intervals (e.g. every 500 m downstream)
• Accessibility: can you reach the river safely? Are there footpaths or bridges?
• Safety: avoid deep water, fast currents, steep banks and private land
• Representativeness: avoid sites immediately after a bridge, weir or tributary confluence (these create localised anomalies)

Typically, you need a minimum of 8–10 sites for meaningful results.

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Data Collection Methods

Channel Width

1. Stretch a tape measure across the river from bank to bank, at right angles to the flow
2. Record the width in metres (to 1 decimal place)
3. Measure at the water's edge, not the top of the bank

Channel Depth

1. Use the same tape measure stretched across the channel
2. At regular intervals across the width (e.g. every 50 cm), lower a metre ruler vertically into the water
3. Read the depth in centimetres or metres
4. Calculate the average depth for the cross section

Velocity

Method 1: Float method

1. Measure a straight 10 m section of the river
2. Place a float (e.g. an orange — it sits half-submerged) at the upstream end
3. Time how long it takes to travel the 10 m
4. Velocity = distance / time (in m/s)
5. Repeat 3 times and calculate the mean
6. Multiply by 0.85 (correction factor to account for friction at the bed and banks)

Method 2: Flow meter / impeller

1. Place the impeller in the water at a set depth (usually 60% of the total depth from the surface)
2. Read the velocity directly from the meter
3. Repeat at several points across the channel and calculate the mean

Bedload Size and Shape

Size:

1. Select 30 pebbles at each site using a random sampling method (e.g. close your eyes and pick one, or use a grid)
2. Measure the long axis of each pebble using a ruler or callipers
3. Record in millimetres
4. Calculate the mean and median pebble size

Shape (roundness):

1. Compare each pebble to Powers' Index of Roundness chart:

Category	Score	Description
Very angular	1	Sharp edges, no rounding
Angular	2	Edges slightly worn
Sub-angular	3	Noticeable rounding of edges
Sub-rounded	4	Well-rounded edges, some flat faces
Rounded	5	Smooth, few flat faces
Well-rounded	6	Very smooth, almost spherical

2. Record the score for each pebble
3. Calculate the mean roundness at each site

Gradient (Slope)

1. Two people stand 10 m apart along the river
2. Person A holds a ranging pole at a known height (e.g. 1.5 m)
3. Person B uses a clinometer to measure the angle between their eye level and the mark on Person A's pole
4. Record the angle in degrees

Alternatively, calculate gradient from contour lines on the OS map: gradient = height loss / horizontal distance.

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Recording Data

Use a recording sheet prepared before fieldwork. Include:

• Site number and grid reference
• Date and time of visit
• Space for each measurement
• Space for notes (e.g. weather conditions, observations, anomalies)

Site	Grid Ref	Width (m)	Mean Depth (m)	Velocity (m/s)	Mean Pebble Size (mm)	Mean Roundness
1	234567	1.2	0.08	0.15	85	1.8
2	238571	1.8	0.12	0.22	72	2.3
...	...	...	...	...	...	...

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Presenting Results

Choose appropriate techniques for each variable:

Variable	Presentation Method
Width downstream	Line graph or bar chart (x = site, y = width)
Depth profile	Cross-section diagram for each site
Velocity	Line graph or scatter graph
Pebble size	Scatter graph (distance downstream vs pebble size)
Pebble roundness	Bar chart or scatter graph
All variables	Summary table with site-by-site data

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Analysing Results

1. Describe the trend — does width/depth/velocity increase downstream? Does pebble size decrease?
2. Use statistics — calculate Spearman's rank to test whether the relationship is significant
3. Identify anomalies — explain possible reasons (e.g. a tributary joining, a weir, a meander bend)
4. Link to theory — compare your results to the Bradshaw model

Exam Tip: When analysing, always refer to the Bradshaw model explicitly. State whether your results agree or disagree with each prediction, and explain why using processes such as erosion, transportation and deposition.

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Common Anomalies and Their Causes