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Coastal defence - summary of human actions
Sea defence (the protection of land from flooding) and coastal protection
(protection of land from erosion) can both apply to shingle beaches and structures.
Building structures (e.g. sea walls and groynes) to 'improve' their coastal
defence capability has occurred on or behind many shingle shores. To some extent
the value of shingle to coastal defence is not recognised until it is too late,
as for example the case of Hallsands (Annex
02) vividly illustrates.
There are four broad approaches to the stabilisation of shingle beaches:
- erection of
structures such as groynes and beakwaters;
- beach
reprofiling;
- beach
nourishment;
- recycling
shingle material.
Each of these has a different impact on the nature of the beach, its ability
to sustain any nature conservation interest and coastal defence capability.
In summary defence works may result in changes to the movement of material both
on and offshore and alongshore. In its turn erosion due to the interruption
of long-shore drift can result in the need for protection further along the
beach. These can all have important consequences for the natural dynamics of
the habitat. The structures themselves can also cause loss of habitat. Beach
nourishment, feeding and re-profiling are also significant activities, the former
having both positive and negative impacts on the habitat, the latter almost
always having negative effects. Beach recycling represents an ongoing activity,
which may have a negative impact on many designated sites.
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Guidance: Shingle
beaches are mobile structures developed in dynamic high-energy
environments.
As such they are themselves highly efficient dissipators of wave energy
and may provide an important natural
defence function. This role should be more readily recognised
when considering coastal defence strategies.
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