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The Holderness coast ,Booklet page 18
A- With reference to a case study, examine the factors which explain coastal erosion. (Not yet
given as a question)
The Holderness Coast is on the NE coast of the UK, facing the North Sea. The Holderness coast is
one of the fastest eroding areas in Britain.
Why is Cliff Erosion such a problem here?
1. The cliffs are made up of soft glacial material (Boulder Clay - made up of sands and gravels). This is
easily eroded by the waves and the cliffs are easily undermined.
2. The Holderness Coast is very exposed, approaching waves have a long fetch over the North Sea.
3. The waves are mainly destructive - eroding the base of the cliffs (hydraulic action etc.)
4. Most of the Material eroded from the cliffs is washed out to sea, the rest is moved by longshore
drift - the beaches are therefore narrow and do little to protect the coastline. (If the beaches were
wider, the waves would break on the beaches reducing their erosive power).
5. The coastline is threatened further by sea-level rise.
1- Geological reasons for erosion: Figure page 18
(i) North around Flamborough Head: headland made of chalk, deeply eroded in parts by erosion
along faultlines and bedding planes. Debris from the chalk cliffs is highly soluble.
Above chalk: unstable unconsolidated glacial till (from glacial deposits) which may slide when
saturated. (Prone to mass movement)
(ii) Moving southward: the majority of the coastline is made of glacial till. These weak clays were laid
down underneath the ice and today are prone to saturation and failure, typically rotational
slumping. Historical records suggest the cliffs are eroding at a rate of 1.5 to 2m per year on
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average.
Where a beach exists that is sufficient to absorb the wave energy without affecting any exposed clay
surfaces, relatively little dam age is done. Long-term change occurs where the beach is worn away
and the underlying clay is removed. Once this has happened, the clay cannot be replaced and
change is more permanent.
Although rising sea levels and the relatively weak nature of the cliff materials largely explain the
physical reason behind the rapid erosion, there may also be some human contributions.
2- Human contributions to erosion
- Dredging of aggregates (gravel) offshore. During 2000, 3,811,044 tonnes of material was removed
under seven licences and there are some concerns that there may be unlicensed dredging going on
close to the shore.
- Defensive hard engineering on existing settlements, e.g. Hornsea, and key communications or
amenities e.g. the gas terminals at Easington. This creates obstacles to the free flow of sediment
southwards and help to retain sand on beaches to the north.
The balance between physical and human influences on coastal erosion is well illustrated by Spurn
Point.
Following the last ice age, longshore drift of sediment eroded from further up the coast built the spit
across the Humber estuary. The tip (end) of Spurn is protected by hard glacial deposits and, inside
this protective rim, sand dunes have created an island. The island is connected to the mainland by a
beach. The island was originally connected to the mainland by a shingle beach. The shingle was
removed in the 18th and 19th centuries to be used as ballast for whaling ships. The removal of shingle
caused the ridge to erode more rapidly and it had to be protected by groynes and sea walls.
However, the fixing of the spit at key points has only served to accentuate the attack elsewhere and
the ridge has now been eroded into a narrow strip. Ultimately, the spit will be completely eroded.
B- With reference to a case study of coastal erosion, assess the relative importance of its physical
and socio-economic consequences.
1- Physical consequences:
Long term change due to erosion of glacial till(briefly explain): the whole coast is gradually
attempting to develop a shape that lies at right angles to the predominant north-easterly wave
direction. As beaches reorient themselves parallel to incoming waves, a wide bay shape is created.
Example of the impacts of Coastal Management: Mappleton
The village of Mappleton is greatly underthreat by coastal erosion along the coastline and by 1998,
the main road running through the village was only 500m from the cliff top and in places it is now
only 50m. The village is under threat due to the easily eroded boulder clay (glacial till) which makes
up the cliff line. The area suffers from erosion rates of up to 2m per year.
Protecting Mappleton
To reduce the amount of erosion threatening Mappleton, 2 rock groynes were constructed in 1991
to encourage the build-up of beach in front of Mappleton by trapping longshore drift. This meant
that that waves would break on the beach rather than attacking the cliffs.
Problems for further down coast
Those living south of Mappleton village have experienced the 'knock-on' effects of the coastal
management. The groynes at Mappleton have disturbed the natural longshore drift movement,
trapping the coastal material. Therefore whilst material is still being moved south of Mappleton,
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there is no fresh sediment to replace it. Beaches have become even narrower and the cliffs are
unprotected. Estimates suggest that it has accelerated cliff erosion south of Mappleton to 10m / yr.
2- Socio-economic consequences.
- Loss of at least 30 villages since Roman times.
- Need for hard engineering to protect settlements such as Hornsea and key communications or
amenities e.g. the gas terminals at Easington (cost £4.5 million). Very high cost to maintain coastal
defences. This cost may become unsustainable. For instance, in 1961, the decision was taken,
following escalating maintenance costs of the defences built to protect Spurn Point, to abandon the
defences and allow natural processes to take control once again.