The Coastal Zone Environment
13
coast like concrete is (even though they are still placed there by humans) and their
capacity to absorb allows the dissipation of wave energy. They also blend into the
natural environment quite well. However, rock revetment schemes do have their
disadvantages. While being cheaper to install than walls, they are more easily damaged
by high energy tides and storms. They are also a form of coast armour, preventing the
sea from removing material to transport to other coastlines, In a similar way to walls
and groynes, they can serve to move the problem of erosion further up the coast.
Erosion can still take place and, as “incident waves are quick to exploit the junction
between protected and unprotected sections” (Carter, 1988, p. 448) it may be expected
that soon there will be more demands for protective measures beyond where they
already exist. Using guidance set out by MAFF, and with the help of SMPs, coastal
managers have to find new techniques for defending the coast and as far as possible,
they must operate in harmony with nature. New methods may still include hard
defences, but increasingly, a soft alternative or natural solution is considered.
Offshore Breakwaters
While not being a truly soft or natural defence mechanism, breakwaters can be useful in
protecting existing defences or vulnerable coasts from the full force of waves, and at the
same time building out the shore, rather than maintaining its line like a solid wall. They
may be part of the harbour or port developments, or integrated into urban shoreline
protection schemes and are usually sited in such a way so as to suffer the full force of
wave impacts (Carter, 1988). The most common design comprises a core of loose fill,
overlain by a veneer of large interlocking riprap or armour units (Carter, 1988).
Breakwaters may be utilised in two ways:
1)
2)
to dissipate and reflect wave energy.
to promote sedimentation.
Breakwaters placed offshore in the front of a sea wall serve to reduce the force
of the incoming waves, and may also prevent some beach scouring that reflection from
walls can cause. Likewise, breakwaters in front of soft erodable beaches may lessen the
force of the wave attack and hinder removal of material. More subtle use of breakwaters
can encourage sedimentation at beaches. Strings of shore-parallel breakwaters
interposed between the beach and incident waves create wave shadows, which may
naturally or artificially infill to produce a stable beach (Carter, 1988). Breakwaters are
not without their own disadvantages. Similarly, offshore breakwaters designed to trap
sediment may contribute to erosion on adjacent shores. The problem of erosion merely
shifts to another location. Carter (1988) also argues that breakwaters are subject to
failure: "They are exposed and prone to storm damage and may, therefore, be expensive
to maintain".
Beach Nourishment
A soft natural defence scheme is beach nourishment, the importing of foreign material
13
coast like concrete is (even though they are still placed there by humans) and their
capacity to absorb allows the dissipation of wave energy. They also blend into the
natural environment quite well. However, rock revetment schemes do have their
disadvantages. While being cheaper to install than walls, they are more easily damaged
by high energy tides and storms. They are also a form of coast armour, preventing the
sea from removing material to transport to other coastlines, In a similar way to walls
and groynes, they can serve to move the problem of erosion further up the coast.
Erosion can still take place and, as “incident waves are quick to exploit the junction
between protected and unprotected sections” (Carter, 1988, p. 448) it may be expected
that soon there will be more demands for protective measures beyond where they
already exist. Using guidance set out by MAFF, and with the help of SMPs, coastal
managers have to find new techniques for defending the coast and as far as possible,
they must operate in harmony with nature. New methods may still include hard
defences, but increasingly, a soft alternative or natural solution is considered.
Offshore Breakwaters
While not being a truly soft or natural defence mechanism, breakwaters can be useful in
protecting existing defences or vulnerable coasts from the full force of waves, and at the
same time building out the shore, rather than maintaining its line like a solid wall. They
may be part of the harbour or port developments, or integrated into urban shoreline
protection schemes and are usually sited in such a way so as to suffer the full force of
wave impacts (Carter, 1988). The most common design comprises a core of loose fill,
overlain by a veneer of large interlocking riprap or armour units (Carter, 1988).
Breakwaters may be utilised in two ways:
1)
2)
to dissipate and reflect wave energy.
to promote sedimentation.
Breakwaters placed offshore in the front of a sea wall serve to reduce the force
of the incoming waves, and may also prevent some beach scouring that reflection from
walls can cause. Likewise, breakwaters in front of soft erodable beaches may lessen the
force of the wave attack and hinder removal of material. More subtle use of breakwaters
can encourage sedimentation at beaches. Strings of shore-parallel breakwaters
interposed between the beach and incident waves create wave shadows, which may
naturally or artificially infill to produce a stable beach (Carter, 1988). Breakwaters are
not without their own disadvantages. Similarly, offshore breakwaters designed to trap
sediment may contribute to erosion on adjacent shores. The problem of erosion merely
shifts to another location. Carter (1988) also argues that breakwaters are subject to
failure: "They are exposed and prone to storm damage and may, therefore, be expensive
to maintain".
Beach Nourishment
A soft natural defence scheme is beach nourishment, the importing of foreign material