YEAR 10 Fieldwork
A Case Study of Coastal Change and Management
Dunwich and Aldeburgh (The Suffolk Coast)
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From the shingle ridge by Dunwich car park we could clearly see coastal processes in action. The coast is a system, eroding material (input), transporting material (throughput) and depositing material (output) along the coast. There are four main ways in which coasts erode:
 | Attrition - pebbles in the water hit against each other and become smaller |
| Hydraulic Action - sheer power of the wave causing erosion - forced into cracks in the cliff, compressing air and forcing cracks open. |
| Abrasion (Corrasion) - rocks carried by the waves are flung against the cliff gradually eroding it. |
| Solution (Corrosion) - some minerals such as calcium carbonate are easily dissolved and carried away in solution. |
Erosion of the cliffs at Dunwich
The rate of cliff erosion is influenced by a number of different factors. These include the nature of the waves (constructive or destructive), the size of the fetch (this is the distance over which the wind has blown, the longer the fetch the larger the wave), the strength of the wind (stronger winds produce waves with more energy to erode) and the nature of the material making up the beach and cliff line.
The low cliffs at Dunwich are made up of layers of soft sands and gravels (Norwich Crag), and boulder clays. These materials are easily eroded by the action of waves and sub-aerial weathering influences further destruction of the cliffs. The high tides and the narrow beach in front of the cliffs (little reduction in wave energy before waves hit the cliffs) cause fairly rapid erosion. The cliffs at Dunwich are retreating rapidly at a rate of about one metre per year. Erosion is greatest in Autumn and Winter when strong winds, storms and associated destructive waves can cause rapid erosion. In one storm in 1990 over 7m of the coast was lost in a few days!
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We spent some time studying the cliff profile, looking for signs of erosion and making field sketches.
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