Geoscience Reference
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increase over time at least as a result of the demands on the coasts
[EMS 10]. All the large companies, e.g. Lafarge in Europe, are
looking for areas from which to extract sediments. These are found
under two categories, either as fossil sand and gravel deposits left to
settle over the latest transgression (or over repeated transgression-
regression oscillations during the Quaternary), at depths that are
known due to increasingly precise cartography; or as “living”
structures, i.e. all the shoals and “ridins” of the platform mobilized by
the swells.
This type of exploration tends to increase the cost of sand or
gravel by cubic meter, and is therefore in conflict with the
technical capacities for extracting and transporting sediments to
the coasts. It is also in conflict with the constraints from the
regulations for environmental protection due to the benthic
life that inhabits it, to the reluctance of fishermen themselves and
finally to the mobilization of associations for the protection of the
environment.
A typical example of this is the extraction site targeted by Lafarge
at about 40 m depth off Groix, facing the Plouharnel beaches. In this
area, the fear is to see the shoreline retreat through adaptation of the
foreshore profile to the created trench. It was a similar worry that
mobilized in vain organizations opposing the exploitation of the ridge
of Pilier off the Island of Noirmoutier.
In the future, the exploration of potential sites will have to be
carried out in a more flexible framework offered by the integrated
management of coastal zones. It represents, along with offshore wind
farm sites, one of the greatest challenges for marine spatial planning,
which is still in its infancy. It is also a way of improving our
understanding of the foreshore dynamics. However, in the United
States or the Netherlands, for example, where sediments are used
regularly to refill the beaches as a common practice to fight the sea,
the volumes needed are so massive that the requirements there again
are likely to increase, especially in the face of sea level rise. A slight
increase of the level of the ocean could accelerate a worrying
phenomenon.
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