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River Fieldwork » River Fieldwork Enquiry

What you'll learn this session

Study time: 30 minutes

Edexcel spec: 1.4

How to investigate river processes and form with primary fieldwork: width, depth, velocity, gradient and sediment
How to use field sketches and photographs to show change downstream
How to use a GIS topographic map and local river flow data as secondary sources
How to apply all this to unfamiliar river data in the exam

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The river enquiry in Section B

Section B of Paper 1 tests one geographical enquiry with fieldwork. If your topic is River environments, your enquiry is an investigation of river processes and form through primary and secondary fieldwork evidence. The spec says your primary data must include both quantitative and qualitative techniques, and your secondary data must use at least two different sources. For the theory behind rivers, see the River Environments lessons. This lesson is about the fieldwork itself.

Key terms:

Channel measurements: measurements of the river itself: width, depth, velocity and gradient.
Velocity: how fast the water flows, usually in metres per second (m/s).
Gradient: how steeply the river channel or valley slopes.
Sediment: the pieces of rock, such as pebbles and sand, found in or beside the river.
GIS: a Geographic Information System, which shows data as layers on a digital map.

Primary quantitative data: channel measurements

The spec suggests two sets of quantitative measurements. The first is the channel: velocity, width, depth and gradient. Students usually repeat them at several sites from upstream to downstream, so that they can compare places.

📏 Width and depth

Stretch a tape measure across the channel from bank to bank for width. Then use a ruler or measuring stick to take depth readings at equal spaces across the channel.

🌊 Velocity

Time a float, such as an orange, over a marked distance, or use a flow meter. Repeat the reading, because the water moves faster in the middle than at the edges.

📐 Gradient

Use a clinometer or ranging poles to measure the slope of the river between two points. The gradient is the angle of that slope.

🔍 Sediment

Pick a sample of pebbles. Measure the size of each (usually the longest axis) with a ruler, and judge the shape by how rounded or angular each pebble is.

Worked example

On the River Kelda, a student times a float over a 10 metre stretch. The three timings are 18 s, 20 s and 22 s.

Mean time = (18 + 20 + 22) ÷ 3 = 20 s.

Velocity = distance ÷ time = 10 ÷ 20 = 0.5 m/s.

Sediment size and shape are measured because they give clues about the river's processes. Pebbles that are small and rounded have usually travelled further and been worn down on the way.

Primary qualitative data: sketches and photographs

The spec suggests two qualitative methods for rivers.

Annotated field sketches of the river channel and its features. Draw the main outlines, then add labels that describe and explain, such as "steep bank, undercut by erosion" or "wide, shallow channel with gravel bar".
Photographs to show how the channel changes downstream. Take them at each site from the same angle, include something for scale, and annotate them.

Put the sketches or photographs from different sites side by side. The change in the size of the channel, the banks and the sediment can then be seen at a glance, and they support the numbers from your measurements.

Secondary data for a river enquiry

The spec suggests two secondary sources for rivers:

🗺 A GIS topographic map

For example from ArcGIS Online or Google Earth. It shows the course of the river, its valley, contours and nearby land use, so you can see the gradient and the setting of your sites.

📊 Local flow data

Local secondary data on river flows or regimes. It shows how the amount of water in the river changes through the year or during a storm, which helps you judge how typical your own readings were.

What the data may show

When you compare sites from the upstream section to the downstream section, you would often expect the river to get wider and deeper, to flow faster, to have a gentler gradient and to have smaller, more rounded sediment. Your own results may not match this. A tributary, a bend or a weir can all cause an odd result, and a good answer explains it.

Unfamiliar fieldwork in the exam

Some questions are set in a familiar context (your own enquiry), and some in an unfamiliar one. In an unfamiliar question the examiner gives you new river data, collected using the same kinds of methods, and you apply your fieldwork understanding to it. You are not expected to know the river. You should be able to:

describe a pattern using figures taken from the data, and spot any exception
explain the pattern using what you know about how rivers change
say how a method works, and what might make a result unreliable
say how a source such as a GIS map or flow data would help

Common mistakes

Timing the float only once, or only in the middle of the channel.
Writing "the river gets bigger" with no numbers. Always quote figures from the table.
Forgetting that photographs and sketches are qualitative, and that your enquiry needs both kinds of data.
Measuring only the biggest or the most interesting pebbles. This is biased, so choose them without looking.
Treating one odd result as a mistake without suggesting a reason for it.

Exam-style question

A student studied the River Alder at four sites, from near the source to the mouth. The table shows the results.

Site	Distance from source (km)	Gradient (degrees)	Mean pebble length (mm)	Velocity (m/s)
1	2	8	80	0.2
2	6	5	55	0.4
3	10	3	35	0.6
4	14	1	20	0.8

(a) Describe how the velocity changes downstream. [2 marks]

(b) Suggest one reason why the sediment becomes smaller downstream. [2 marks]

(d) Describe one way the student could make the velocity results more reliable. [2 marks]

Model answer

(a) Velocity increases steadily downstream (1) from 0.2 m/s at site 1 to 0.8 m/s at site 4 (1).

(b) Pebbles knock against each other and the river bed as they are carried along, so they are worn down into smaller pieces (1). The further downstream they travel, the more they are worn, so the pebbles at site 4 are smaller (1).

(c) It shows the river's course and the contours, so the student can see how steeply the land slopes between sites (1) and check that the sites are spread along the river from the source to the mouth (1).

(d) Time the float several times at each site (1) and calculate a mean, so that one odd reading does not affect the result (1).

Exam tip

In (a), a pattern answer needs figures from the table. Quote a start value and an end value, with units.

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