II. Coastal Mana[ement and Coastal Defense
3
Accommodation
27
The implications of this option would be a compromise between retreat and
protection. However, resource exploitation practices would change. For example,
people may harvest mangrove wood for use as pilings to elevate houses. Flood
control efforts might alter water flow patterns which could adversely affect the
coastal environment.
4
Protection
This strategy is most relevant for areas having relatively large populations and an
important infrastructure. These conditions inherently alter the environments.
However, the structural measures related to a protection strategy can impose
additional alterations not only to the immediate environment but also to the
unaltered coastal ecosystems beyond the area of protection. Therefore,
environmental impact assessments (E.I.A.) are particularly important when
protective measures are envisaged. A subsidiary social impact assessment (S.I.A.)
may be considered (cf. 4,1.).
4.1
Hard Structures
Along ocean coasts, a sea-wall constructed landward of the shoreline would have
little immediate impact on the beach systems. However, an eroding shore would
eventually reach the sea-wall and result in a loss of the natural beach 8. This
impact can be avoided by means of beach nourishment. Similarly, structures
could block the inland migration of coastal wetlands. For example, in the United
States, the loss from a one meter rise would be 29-66 percent under the retreat
option, but 50-82 percent if shores are protected with bulkheads 9.
Groins trap sediment moving along the shore. However, protection of one area is
generally at the expense of increased erosion downdrifl from the protected area.
Because these structures do not increase the total sediment available to beaches
and barrier islands, their long term impact is primarily a geographic shift of the
erosion. Detached breakwaters often have similar effects, although they allow for
nearshore habitat shifts in some cases and often provide desirable fish habitats
("artificial reefs") in much the same fashion as natural reefs.
3
Accommodation
27
The implications of this option would be a compromise between retreat and
protection. However, resource exploitation practices would change. For example,
people may harvest mangrove wood for use as pilings to elevate houses. Flood
control efforts might alter water flow patterns which could adversely affect the
coastal environment.
4
Protection
This strategy is most relevant for areas having relatively large populations and an
important infrastructure. These conditions inherently alter the environments.
However, the structural measures related to a protection strategy can impose
additional alterations not only to the immediate environment but also to the
unaltered coastal ecosystems beyond the area of protection. Therefore,
environmental impact assessments (E.I.A.) are particularly important when
protective measures are envisaged. A subsidiary social impact assessment (S.I.A.)
may be considered (cf. 4,1.).
4.1
Hard Structures
Along ocean coasts, a sea-wall constructed landward of the shoreline would have
little immediate impact on the beach systems. However, an eroding shore would
eventually reach the sea-wall and result in a loss of the natural beach 8. This
impact can be avoided by means of beach nourishment. Similarly, structures
could block the inland migration of coastal wetlands. For example, in the United
States, the loss from a one meter rise would be 29-66 percent under the retreat
option, but 50-82 percent if shores are protected with bulkheads 9.
Groins trap sediment moving along the shore. However, protection of one area is
generally at the expense of increased erosion downdrifl from the protected area.
Because these structures do not increase the total sediment available to beaches
and barrier islands, their long term impact is primarily a geographic shift of the
erosion. Detached breakwaters often have similar effects, although they allow for
nearshore habitat shifts in some cases and often provide desirable fish habitats
("artificial reefs") in much the same fashion as natural reefs.