|
Coastal vegetated shingle - index to States
Shingle beaches
Shingle beaches and structures erode and accrete at their seaward margin. On
narrow fringing beaches, periodic movement occurs in response to tidal movement
and storms. The former help to move the beach material along the shore, the
latter may force major repositioning of the beach often in a landward direction.
Two states can be described for shingle beaches namely:
Whilst these state may exist in a dynamic equilibrium it is often the case
that erosion predominates in areas where shingle has been extracted from reserves
offshore or from the beach itself. This not only results in the loss of surface
vegetation but can also have adverse consequences for the sea defence capability
of the beach.
Shingle structures
A very different situation arises where more substantial structures exist and
both ephemeral
and stable shingle surfaces are present. Here the issues surrounding restoration
are largely concerned with restoring damaged surface shingle, its vegetation
and associated animal interests. Although the issues surrounding restoration
of the surface shingle can be linked to the re-establishment of shingle dynamics
the methods of restoration are considered separately. Thus two states are identified:
- State
3 Mature stable vegetated shingle;
- State
4 Surface shingle damaged or destroyed.
A fifth State
5 is recognised where the shingle is excavated to below the water
table resulting in the development of open water gravel pits. The 'values'
of each of these states is described together with some more specific information
on birds,
invertebrates
and lichens.
Caveat: At the seaward edge of a shingle beach erosion and accretion
are the norm. They can exist in a dynamic equilibrium and develop with or without
ephemeral
vegetation. Whether the shingle site is assigned to the erosional (State
1) or accretional (State
2) forms depends on the net sediment budget being negative in the
former or positive or neutral in the latter.
|
