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Unlock This CourseIf your Section B topic is Coastal environments, your enquiry is an investigation of coastal processes and form through primary and secondary fieldwork evidence. As in the River Fieldwork Enquiry lesson, you need both quantitative and qualitative primary data, and at least two different secondary sources. The theory of waves, erosion and landforms is in the Coastal Environments lessons. This lesson is about collecting and using the evidence.
Key terms:
The spec suggests two sets of measurements for a coastal enquiry.
Choose pebbles at set spaces along the beach without looking, so the sample is not biased. Measure the longest axis of each with a ruler. Judge the shape on a scale, such as 1 for very angular up to 5 for very rounded.
Run a line from the sea to the back of the beach. Place a ranging pole at each change of slope and use a clinometer to read the angle between two poles. Measure the distance between them with a tape.
Measure a cliff or the intertidal zone. For a cliff, record its height, the angle of its face and signs of erosion such as notches or fallen rock. For the intertidal zone, measure the width of shore between the high and low tide marks.
A beach profile has four sections, each 10 m long. The clinometer readings of the slope are 2°, 4°, 9° and 12°, going from the sea up the beach.
Every reading is bigger than the one before, so the beach gets steeper towards the back. The lowest section (2°) is almost flat, and the top section (12°) is the steepest.
Sediment size and shape give clues about the processes at work. Pebbles that are small and rounded have usually been moved and worn down more than large, angular ones. You can look at this along the beach, or compare beaches.
Again there are two methods.
Putting the sketches or photographs from different points side by side lets you see changes in the cliffs, beach and shore at a glance. They back up your measurements.
Check the tide times before you go, so you are not cut off. Never stand directly below a cliff, because rock can fall. Wear sensible footwear, and stay with your group. This is part of your risk assessment.
The spec suggests two secondary sources for coasts.
On paper or digital. It shows which rock types are found along your stretch of coast, so you can see whether changes in the cliffs or bays might be linked to the rock. The reasons are in the Geological Influences on Coasts lesson.
For example historic maps. Comparing an old map with a modern one shows how the coastline has changed.
On a map from 1900, a cliff edge is 60 m from a coastal lane. On a modern map the edge is 36 m from the lane.
Retreat = 60 − 36 = 24 m. Time = 120 years. Rate = 24 ÷ 120 = 0.2 m per year.
This assumes the old map is accurate, so say that in an evaluation.
You may find that pebbles get smaller and rounder in one direction along a beach, or that the beach is steeper at the back than near the sea. Your results may not fit the pattern. A groyne, a river mouth or a change in the cliff rock can all cause an odd result, and a good answer suggests a reason for it.
An unfamiliar question gives you new coastal data collected with the same kinds of methods. You are not expected to know the place. You should be able to:
A student studied Marram Bay at three points along the beach, going from west to east. The table shows the results.
| Point | Mean pebble length (mm) | Mean roundness (1 = angular, 5 = rounded) | Beach slope (degrees) |
|---|---|---|---|
| 1 | 64 | 2 | 12 |
| 2 | 46 | 3 | 8 |
| 3 | 28 | 4 | 5 |
(a) Describe how the pebble length changes from west to east. [2 marks]
(b) The student also took a photograph at each point. Give one way the photographs could be used. [2 marks]
(c) Explain how historic maps could help the student investigate Marram Bay. [2 marks]
(d) Suggest one reason why the pebble results might be unreliable. [2 marks]
(a) Pebble length decreases from west to east (1), from 64 mm at point 1 to 28 mm at point 3 (1).
(b) They can be annotated to show variations along the stretch of coast (1), such as a change in the beach or cliff between the points (1).
(c) Comparing an old map with a modern one shows where the coastline has moved (1), so the student can work out how much the coast has changed over time (1).
(d) Only a small number of pebbles may have been measured at each point (1), so a few unusual pebbles could change the mean (1).
In (a), a pattern answer needs a start and end figure with units. Say "decreases" and give the numbers.