Fieldwork Case Studies and Problems in the Field – Fieldwork Techniques (Senior 4 Geography) | Ganzaa

Fieldwork Techniques

Lessons

Senior 4 · Geography

Fieldwork Techniques

4 lessons

Lesson 4 of 4

Fieldwork Case Studies and Problems in the Field

25 min

Eight places to study

The methods of the last three lessons fit together differently in each kind of place. The table matches the kinds of fieldwork study named in the S4 syllabus with a question worth asking and the methods that answer it. Choose the one nearest your school for your own study.

Study area	A question to investigate	Main methods and data
The school area	How is the school compound used, and is it warmer on tarmac than under trees?	Land-use map from pacing and a sketch plan; thermometer readings at several sites at the same time
A river valley	How do width, depth, velocity and discharge change downstream?	Tape, metre rule, float and stopwatch at several sites; valley cross-profile with clinometer; land use on the slopes
Landforms (a hill, a gully)	How do slope angle and erosion change down a hillside?	Slope profile with poles and clinometer; gully width and depth; field sketch; photos
An urban area	How does land use change from the town centre outwards?	Land-use transect, building heights, pedestrian counts, questionnaires on services
A rural settlement	What pattern do the houses form, and what services do people use?	Sketch map, counts of house types, interviews with the village leader, questionnaires
A market	How far do traders and shoppers come, and what do they trade?	Questionnaires (origin, goods), counts of stalls by type, a map of origins
A fishing site	How is fish caught, preserved and sold?	Observation of boats and nets, interviews with a cooperative leader, counts of the catch
A plantation	How are land, labour and processing organised on a tea or sugar estate?	Key informant interview with the manager, observation of plucking and processing, sketch map of the estate

Case study: a river valley

A stream is the classic fieldwork site because it can be measured completely. At each site downstream the class measures four things:

Width of the water surface, with a tape stretched from bank to bank.
Depth with a metre rule at equal intervals across the channel.
Surface velocity: time a float (an orange, a stick) over a measured distance, usually 10 m, three times.
Discharge, calculated from the cross-sectional area and the velocity.

Definition

Discharge ( $Q$ ): the volume of water passing a point in a river each second, in cubic metres per second ( $\mathrm{m^3\,s^{-1}}$ , also called cumecs).

Q = A \times v

where $A$ is the cross-sectional area of the water ( $\mathrm{m^2}$ ) and $v$ the mean velocity ( $\mathrm{m\,s^{-1}}$ ). Example: $A = 2\ \mathrm{m^2}$ and $v = 0.5\ \mathrm{m\,s^{-1}}$ give $Q = 1\ \mathrm{m^3\,s^{-1}}$ .

Worked example 1: the discharge of a stream

Data. The stream is 4.0 m wide. Depths taken every 0.5 m from the left bank are 0, 0.20, 0.35, 0.50, 0.60, 0.55, 0.40, 0.25 and 0 m (Figure 7). A float takes 16.2 s, 15.4 s and 16.8 s to travel 10 m.

Area. Each 0.5 m strip is a trapezium, so $A = \sum \frac{d_i + d_{i+1}}{2} \times 0.5$ . Because both end depths are 0, this simplifies to 0.5 m times the sum of the inner depths:

A = 0.5 \times (0.20 + 0.35 + 0.50 + 0.60 + 0.55 + 0.40 + 0.25) = 0.5 \times 2.85 = 1.43\ \mathrm{m^2}

Velocity. Mean time $= \frac{16.2 + 15.4 + 16.8}{3} = 16.13$ s, so the surface velocity is

v_{\text{surface}} = \frac{10}{16.13} = 0.620\ \mathrm{m\,s^{-1}}

Water near the bed and banks is slowed by friction, so the mean velocity is less than the surface velocity. A correction factor of about 0.8 is used for a stony bed:

v = 0.8 \times 0.620 = 0.496\ \mathrm{m\,s^{-1}} \qquad Q = A \times v = 1.425 \times 0.496 = 0.71\ \mathrm{m^3\,s^{-1}}

The stream carries about 0.71 cubic metres of water every second at this site.

Figure 7: the stream's cross-section from the depth readings in Worked example 1.

Warning

Safety first in a river. Work only in water shallower than knee-depth, on a straight, slow stretch, never after heavy rain and never alone. Wear shoes, keep away from steep banks, and do not enter water that may be polluted. A study can be done entirely from the bank if needed: measure width with the tape and velocity from a bridge.

A shallow, stony stream at Mutobo, Rwanda, 30 March 2021, with grassy banks and a small bridge behind. A straight stretch like the foreground, with water well below knee depth, is the kind of site where width, depth and float timings can be taken safely. Photo: Alice.Mukesh, CC BY-SA 4.0, via Wikimedia Commons.

Problems in planning and carrying out fieldwork

Problem	Example	Possible solution
Cost of transport, materials and food	A bus to a distant site for a whole class	Choose sites near the school; share materials; plan the budget early
Weather	Rain makes notes illegible and rivers dangerous	Plan for the dry season; carry plastic bags for notebooks; have a reserve date
Permission and access	A farm or factory refuses entry	Write letters early through the school; agree the visit with the sector or the manager
Suspicious or busy respondents	Traders refuse questions at the busiest time	Explain the purpose, carry the school letter, keep questions short, ask at quiet times
Language	Questions written in English only	Prepare and pilot a Kinyarwanda version
Faulty or missing instruments	No clinometer for a slope profile	Test instruments beforehand; make simple ones (a protractor, string and weight)
Too little time	A large area and one afternoon	Narrow the aim; divide the class into groups with separate tasks
Safety	Traffic, deep water, steep slopes	Risk assessment; groups, never alone; a teacher present; first-aid kit
Unreliable data	Respondents give the answers they think you want	Avoid leading questions; check answers against observation and secondary data

Tip

Exam technique. When asked for problems of fieldwork, pair each problem with a practical solution, and keep them specific to the study named in the question. "Rain" is weak; "heavy rain raised the river, so depth readings at site 3 were unsafe; we returned two days later" is strong.

Geography Teacher: "Measuring the velocity of the river". A short fieldwork demonstration of timing a float along a measured stretch of river. Compare it with the method in Worked example 1, and note how many timings are taken.

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Practice

For a study of a rural settlement, write one hypothesis and name three methods you would use.
A stream is 3.0 m wide; depths every 0.5 m are 0, 0.15, 0.30, 0.40, 0.30, 0.20 and 0 m. Find the cross-sectional area.
A float travels 10 m in 20.0 s. Find the surface velocity and, with a correction factor of 0.8, the mean velocity.
Use your answers to questions 2 and 3 to find the discharge.
Why is a float's velocity multiplied by a correction factor less than 1?
Give four problems a class might meet when studying a tea plantation, with a solution for each.
A group measures discharge at a site upstream and a site downstream. The downstream discharge is smaller. Suggest two possible reasons, one natural and one from the method.

Show answersHide answers

For example: "Houses are more clustered near the road than far from it." Methods: sketch map of house positions; counts of houses in zones by distance from the road; interviews with residents on why they settled there.
$A = 0.5 \times (0.15 + 0.30 + 0.40 + 0.30 + 0.20) = 0.5 \times 1.35 = 0.675\ \mathrm{m^2}$ .
$v_{\text{surface}} = \frac{10}{20.0} = 0.50\ \mathrm{m\,s^{-1}}$ ; mean $v = 0.8 \times 0.50 = 0.40\ \mathrm{m\,s^{-1}}$ .
$Q = 0.675 \times 0.40 = 0.27\ \mathrm{m^3\,s^{-1}}$ .
A float measures only the surface, where water moves fastest; friction with the bed and banks slows the water below, so the mean velocity is lower.
For example: entry refused (write early to the manager); workers too busy to answer (interview at breaks, or interview the manager as key informant); a distant estate is costly to reach (share transport, combine with another visit); factory noise and machines are unsafe (follow the guide, keep to safe areas).
Natural: water taken out for irrigation, or seeping into a sandy bed, between the sites. Method: inaccurate depth readings, a float caught in an eddy, or measurements on different days after different rainfall.

Quick check

Key points

Each kind of study area (school, river, landform, town, village, market, fishing site, plantation) has its own questions and methods.
River discharge: $Q = A \times v$ , with the area from depth readings and the velocity from timed floats times a correction factor (about 0.8).
Fieldwork problems include cost, weather, permission, respondents, language, instruments, time, safety and unreliable data; each needs a planned solution.

1Eight places to study

2Case study: a river valley

3Problems in planning and carrying out fieldwork

Eight places to study

Case study: a river valley

Problems in planning and carrying out fieldwork