The Snout of Aberdeen – Groynes at Work
1) Introduction
Aberdeen Beach is more than just a place for a walk or a swim – it is a live demonstration
of an important coastal process called longshore drift.
This EarthCache invites you to observe how sand is moved along the coastline by waves and how wooden
groynes act like a “snout” extending into the sea, interrupting that movement and trapping sand.
By comparing the beach on both sides of a groyne, you can determine the direction of sediment transport
at this location.
2) Geological Background
How longshore drift works
Longshore drift is the movement of sediment along a coastline caused by waves approaching the shore
at an angle.
- Swash: carries sand up the beach in the direction of the incoming wave.
- Backwash: flows straight back down the beach due to gravity.
- Over time, this creates a zig-zag movement and a net transport of sand along the shore.
Why it matters here
At Aberdeen Beach, longshore drift moves sand along the urban shoreline. Without obstacles,
sand would gradually be transported away, leaving the beach lower and narrower and reducing its
ability to absorb wave energy.
3) Groynes – The “Snout” in the Sand
What groynes do
Groynes are wooden barriers built at right angles to the shoreline. They interrupt sediment transport
and encourage sand to accumulate on the updrift side.
The downdrift side often has a lower sand level.
What you should be able to see
- A difference in sand height on either side of the groyne.
- A difference in beach shape (slope or steepness) on either side.
- Natural material (seaweed, shells, or debris) concentrating more on one side.
4) Safety & Tides
- Do not climb the groyne. It can be slippery and unstable.
- If waves are breaking close to the promenade or the groyne is partly covered,
do not go onto the lower beach. Your safety comes first.
- Best time to visit: low to mid tide, when the sand level difference is easiest to see.
High waves or very high tide:
If it is unsafe to stand close to the groyne, all required observations can be made
from the promenade above. From this safe vantage point, you can still compare the
relative sand height, beach shape, and material distribution on both sides of the groyne
and answer the logging questions.
If the groyne is not observable at all due to conditions (for example, completely submerged
or obscured), please return at a safer time or use the next groyne along the beach
and answer the same questions for that groyne.
5) Logging Tasks
To log this EarthCache, please send your answers to the cache owner via message or email.
All answers must be based solely on your own on-site observations.
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Sand Level Comparison
Compare the sand height on the south and north side of the groyne.
Which side is higher, and what visible evidence helped you decide?
-
Direction of Longshore Drift
Based on Task 1, what is the direction of longshore drift at this location?
Explain how the sand distribution supports your conclusion.
-
Beach Shape Observation
Describe the beach shape on both sides of the groyne.
Does one side appear steeper or flatter than the other?
What might this indicate about sediment movement?
-
Wave and Material Evidence
Look for seaweed, shells, or other debris near the groyne.
On which side is it more concentrated, and what does this suggest about wave action
and sediment transport?
-
Interpretation
In your own words, explain why groynes are important for managing erosion
at Aberdeen Beach.
Photos are welcome but not required.
6) Additional Notes
This EarthCache can be completed year-round. Sand levels and beach shape may vary with tides,
weather, and recent storms. These natural changes are part of the learning experience.
Enjoy exploring Aberdeen’s coastline and discovering how natural processes and human structures
interact to shape the beach.