Getting Started with River Fieldwork
Welcome to your study notes for the River Fieldwork Enquiry! Fieldwork is one of the most exciting parts of Geography because it allows you to step out of the classroom and see the processes you've learned about—like erosion and transportation—happening in real life.
In your exam, you will be tested on your own fieldwork experience and your ability to work with unfamiliar data from other river studies. Don't worry if it sounds complicated; fieldwork is just a logical step-by-step investigation into how a river changes from its source to its mouth.
Quick Review: This chapter connects directly to River processes and landforms. You are essentially testing if the "textbook" rules about rivers (like the river getting wider and deeper downstream) are actually true in the real world.
1. Planning Your Enquiry: The Hypothesis
Every good investigation starts with a question or a hypothesis. A hypothesis is a prediction that you can test. For river fieldwork, we usually investigate river processes and form.
Common hypotheses include:
• "The river channel increases in width and depth as distance from the source increases."
• "Velocity increases as the river moves downstream."
• "Sediment size decreases and becomes more rounded downstream."
Risk Assessment
Before heading to the river, you must consider safety. This is called a risk assessment.
• Risk: Slippery rocks. Precaution: Wear sturdy boots with good grip.
• Risk: Deep or fast-flowing water. Precaution: Check depth with a ranging pole before entering; do not enter if the water is above knee height.
• Risk: Heavy rainfall/flooding. Precaution: Check the weather forecast before leaving.
2. Sampling Techniques
You can’t measure every single centimetre of a river! Instead, you use sampling to pick specific locations.
• Random Sampling: Choosing sites by chance (like picking coordinates from a hat). It avoids bias but might miss important parts of the river.
• Systematic Sampling: Taking measurements at regular intervals, for example, every 500 metres downstream. This ensures a good "spread" of data.
• Stratified Sampling: Picking sites based on specific characteristics, such as making sure you have three sites in the upper course, three in the middle, and three in the lower course.
Key Takeaway: Good sampling makes your data more reliable and representative of the whole river.
3. Primary Data Collection (Methodology)
Primary data is information you collect yourself in the field. You need both quantitative (numbers) and qualitative (descriptions/words) techniques.
Measuring the River Channel
• Width: Use a measuring tape pulled taut across the river from one bank to the other at the water's surface.
• Depth: Use a metre ruler or ranging pole. Measure the depth at regular intervals across the width (e.g., every 20cm) and calculate the mean depth.
• Velocity (Speed):
1. Measure a \(10\) metre stretch of the river.
2. Drop a float (like an orange or a cork) at the start point.
3. Use a stopwatch to time how long it takes to reach the end point.
4. Formula: \( \text{Velocity} = \frac{\text{Distance}}{\text{Time}} \).
• Gradient: Use ranging poles and a clinometer to measure the angle of the slope over a set distance.
Measuring Sediment (Bedload)
At each site, pick up a random selection of pebbles from the river bed.
• Size: Measure the long axis of the pebble using a calliper (in millimetres).
• Shape: Use a Powers’ Scale of Roundness to categorize the pebble from "Very Angular" to "Well Rounded." This is a mix of quantitative and qualitative data.
Qualitative Techniques
• Field Sketches: Drawing the river valley and annotating (labelling with descriptions) features like interlocking spurs or meanders.
• Annotated Photographs: Taking a photo and adding labels later to show landforms or land use.
4. Secondary Data Sources
The syllabus requires you to use at least two secondary sources. Secondary data is information gathered by someone else.
• OS Maps (Ordnance Survey): To check the height of the land (contours) and the general route of the river.
• Geology Maps: To see if the rock type changes downstream, which might explain why the river is wider or narrower in some spots.
• Historical Reports/GIS: To look at how the river has flooded in the past or how the channel has moved over time.
Did you know? GIS stands for Geographical Information Systems. It’s like a digital map with layers of data that you can turn on and off!
5. Data Presentation
Once you have your numbers, you need to make them easy to read.
• Tally Charts: Useful for counting types of sediment or land use.
• Scatter Graphs: Great for showing the relationship between two things, like Distance Downstream vs. Pebble Size. You can draw a line of best fit to see the trend.
• Radial Graphs: Can be used to show pebble roundness or flow direction.
• Cross-sections: A graph showing the shape of the river channel (Width on the x-axis, Depth on the y-axis).
Memory Tip: When drawing graphs, always remember TALKS: Title, Axes, Labels, Key, Scale.
6. Analysis and Conclusions
This is where you explain what your data shows.
• Identify Links: "As the distance downstream increased, the mean pebble size decreased from \(55\text{mm}\) to \(12\text{mm}\)."
• Compare with Theory: Does your data match the Bradshaw Model? (The theory that says width, depth, and velocity increase downstream).
• Anomalies: Did you find a result that didn't fit the pattern? For example, a site that was suddenly very shallow. Don't ignore it! Explain it—maybe there was a man-made weir or a recent collapse of the river bank there.
7. Evaluation
The final step is looking back at your work.
• Accuracy: How close were your measurements to the "true" value? (e.g., Was the measuring tape fluttering in the wind?).
• Reliability: If you did the test again, would you get the same results?
• Improvements: How could you make it better? "Next time, we could use a digital flow meter instead of an orange to get a more accurate velocity reading."
Common Mistake: Many students confuse "Accuracy" and "Reliability." Accuracy is about how "right" the measurement is (using a better tool). Reliability is about how "consistent" the results are (doing the test more times).
Key Takeaway Summary:
1. Hypothesize what will happen.
2. Sample the river fairly.
3. Measure width, depth, velocity, and sediment.
4. Present data using clear graphs.
5. Conclude by comparing your results to geographical theories.
6. Evaluate your methods to suggest improvements.