• Fieldwork enquiries are built around geographical theory — for rivers, that's usually the Bradshaw Model
• Every enquiry needs an aim (what you're investigating) and often a hypothesis (a testable prediction)
• Site selection uses sampling (systematic, random, or stratified) to avoid bias
• Specific equipment is used for width, depth, and velocity measurements
• A risk assessment must identify hazards and how to manage them
• Width and depth are measured directly; velocity is measured using a float or flow meter
• Discharge isn't measured directly — it's calculated from cross-sectional area × velocity
• Photographs and field sketches provide qualitative data to support the quantitative measurements

Any piece of river fieldwork needs to be linked back to a piece of geographical theory — you're not just measuring things for fun, you're testing whether reality matches what theory predicts. For rivers, the theory almost always used is the Bradshaw Model.

Think of the Bradshaw Model as a set of predictions for what "should" happen to a river as you travel from its source (upstream) to its mouth (downstream). Picture a river starting as a thin, rocky trickle in the hills and ending as a wide, slow-looking, muddy giant near the sea — the Bradshaw Model is the theory that explains exactly how and why that transformation happens.

Variables that increase downstream

Variables that decrease downstream

Notice the pattern: five variables increase downstream (discharge, width, depth, velocity, load quantity) and three variables decrease (particle size, bed roughness, gradient). A river fieldwork enquiry is essentially a way of testing: "does my real river actually follow the Bradshaw Model, or does something local — like a confluence, a dam, or a different rock type — make it behave differently?"

Before you go anywhere near a river with a tape measure, you need to know exactly what question you're trying to answer. This comes in two closely related forms:

Here's the key distinction that trips people up in exams: an aim sounds like "An investigation into how X changes downstream", whereas a hypothesis sounds like "X will increase with distance downstream." The hypothesis commits to a direction; the aim just states the topic.

Once you have your aim and hypothesis nailed down, the fieldwork process follows a set order:

1. Select the sites (this involves sampling — see next section)
2. Decide on the equipment to be used
3. Consider health and safety issues (risk assessment)
4. Choose your data collection method

You physically cannot measure every single point along a river — it's too long, and you don't have time. So you need a smart way of choosing a manageable number of sites that still gives you a fair, representative picture of the whole river. That's what sampling is for: it reduces bias, meaning it stops you (even accidentally) from picking sites that only support the result you're hoping for.

Sometimes the river simply won't let you follow your sampling plan exactly — maybe a section is on private land, or too dangerous to reach. In that case you take an opportunistic approach: picking the closest safe, accessible point to your originally planned site.

The three sampling strategies

Each piece of kit in a river fieldwork toolkit has one specific job. Learn what does what — exam questions love testing this directly (e.g. multiple choice "which piece of equipment measures X").

Every fieldwork trip needs a proper think-through of health and safety before anyone sets foot near the water. In an exam, risk-assessment questions almost always come in a pair: first identify a risk, then suggest how to manage it. Always keep the two linked — a management strategy only earns marks if it clearly fixes the risk you named.

What you measure depends entirely on your aim and hypothesis, but nearly every river enquiry starts in the same place: measuring width and depth. Good fieldwork also balances two types of data:

Measuring Width

Width is measured at the point where the water surface touches each bank — from the "wet edge" on one side, straight across, to the "wet edge" on the other side.

• Measure from where the dry bank meets the water on one side, to where it meets the water on the opposite side.
• Hold the tape taut (tight, not sagging) and make sure it doesn't touch the water — a wet, sagging tape gives an inaccurate, unreliable reading.

Measuring Depth

A single depth reading tells you almost nothing, because rivers are deeper in the middle and shallower near the banks. So depth is measured at regular intervals across the whole width — this builds a full cross-sectional picture and lets you calculate a reliable mean depth, which you'll need later for the discharge calculation.

1. Work out the distance apart each depth measurement needs to be (e.g. width ÷ number of readings)
2. Place a metre rule into the water at the correct point
3. Hold the ruler sideways, flat side facing the banks — this cuts down on turbulence around the ruler, giving a more accurate water-height reading
4. Record the distance from the riverbed to the water surface
5. Repeat across the entire width

Measuring Velocity

Velocity is how fast the river is flowing, and — just like depth — it isn't the same everywhere across the channel. Friction with the banks slows the water down at the edges, so readings are taken at three positions: towards the left bank, the centre, and towards the right bank.

Using a flow meter:

• Take readings at the three equal positions across the width
• Place the flow meter at least 3cm below the surface (surface water is affected by air resistance and isn't representative)
• Take three readings at each of the three positions, so you can calculate a reliable mean

Using a float (if no flow meter is available):

1. Measure a set distance upstream — e.g. 10 metres
2. Drop the float in at the start of that 10m stretch
3. Time how long it takes to travel the distance, using a stopwatch
4. Repeat three times at each position to calculate a mean

Here's a crucial idea that trips a lot of students up: discharge is never measured directly with a piece of equipment — it's always calculated, using the width, depth and velocity data you've already collected. Think of it as the final step that combines everything else into one meaningful number: the total volume of water passing a point every second.

Numbers alone can't capture everything about a river — that's where qualitative evidence comes in. Photographs and field sketches let you record landforms and features (like bed load, meanders, or bank erosion) that would be hard to describe fully in a data table. Photographs are also great for showing exactly how your data collection methods were carried out, which can support the reliability of your fieldwork.

• I can explain what the Bradshaw Model predicts, and give a reason for at least one variable increasing and one decreasing
• I can write a clear aim AND a clear hypothesis, and explain the difference between them
• I can name and describe all three sampling strategies (systematic, random, stratified) and say when each is useful
• I know which piece of equipment measures which variable (width, depth, velocity)
• I can identify a river fieldwork risk and pair it with a specific, matching management strategy
• I know how to measure width correctly (wet edge to wet edge, taut tape)
• I know why depth is measured at regular intervals and why the ruler is held sideways
• I know why velocity is measured at three positions across the channel
• I can calculate cross-sectional area from width and mean depth
• I can calculate discharge from cross-sectional area and velocity, showing full working in the correct units
• I can explain the difference between quantitative and qualitative data in a river enquiry
• I know the difference between a label and an annotation on a field sketch

What examiners are looking for

• Precise, technical vocabulary — "cross-sectional area," "attrition," "systematic sampling" rather than vague description
• Clear step-by-step working in calculation questions — marks are often awarded for method, not just the final number
• Linked answers — a risk paired with its matching management strategy, an aim that matches the theory being tested
• Justification, not just description — explain why a method (e.g. holding the ruler sideways) improves accuracy