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Shingle beaches and coastal defence
Because they respond to storms and sea level change by migrating alongshore
or landwards shingle beaches and structures can expose the hinterland to the
forces of erosion. Where the coast is eroding the normal response has been to
protect the shingle at the point of erosion by the construction of groynes,
breakwaters, gabions
or other structures to prevent landward movement or long shore drift. Reprofiling
the beach, beach
nourishment and recycling
are also employed. In areas where the threat from flooding is the main concern
embankments are built.
As a general rule since the early 1970s the reliance on hard defensive structures
has been questioned not least because they have proved to be ineffective in
some situations (e.g. Porlock;
Cley)
and caused accelerated erosion downdrift from the 'protected' coast. As a result
beach
nourishment (recharge) has gained acceptance as a means of restoring
the sea defence capabilities of the shingle beach/structure (Coates
et al. 2001). These issues are considered in more detail in the "Guide
to management and restoration of coastal vegetated shingle".
| Guidance: An important point to consider in relation
to these approaches, is that many of the beach-barrier systems on the modern
coast were initiated during the Holocene marine transgression and are now
responding to changes in sea level, storms and tidal movement involving
the reworking of an essentially finite sediment supply (Pye
2001). This poses the most significant management issue in relation
to the sustainability of coastal shingle beaches and structures, especially
for sea defence purposes. This issue has been the subject of a major European
Community funded project (BERM)
which aims to assess the extent to which shingle beaches of Rives-Manche
(Channel coast) have been depleted and the implications for sea defences
in the region in the face of rising sea levels. |
Caveat: Cheniers
are considered in some areas to have the potential to act as a natural sea defence..
References
Coates, T.T., Brampton, A.H. & Powell, K.A.
2001.
Shingle beach recharge in the context of coastal defence: principles and problems.
In: Ecology & Geomorphology of Coastal Shingle, eds.Packham, J.R., Randall, R.E., Barnes, R.S.K. & Neal, A.Westbury Academic and Scientific Publishing, 394-402.
Pye, K.
2001.
The nature and geomorphology of coastal shingle.
In: Ecology & Geomorphology of Coastal Shingle, eds.Packham, J.R., Randall, R.E., Barnes, R.S.K. & Neal, A.Westbury Academic and Scientific Publishing, 2-22.
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