Vulnerability, Impacts and Adaptation of Coastal Zones to Global Change - Vulnerability of Coastal Ecosystems and Adaptation - page 161

Protection consists of advancing or holding the coastline using
various options, such as beach and dune nourishment, ecosystem
restoration and the construction of hard coastal defense structures.
These can be seawalls, sea dykes, groynes and storm surge barriers.
While seawalls aim to hold the coastline and to avoid flooding or
submersion of low-lying land, transverse structures retain part of the
sediments moving parallel to the coast. The hard engineering options
are in general relatively costly, complex and have a limited lifespan.
Planning of such options should take account of the uncertainties
associated with the socio-economic and climate change scenarios and
the side effects that they can have on the medium- and long-term local
and regional coastal zone dynamics.
Accommodation privileges the change in human coastal activities
and flexible adaptation of the built environment and infrastructures,
such as the adaptation of buildings to make them more resistant to the
effects of GMSL rise, the lifting of bridges and other transport
infrastructure, the construction of flood shelters, flood proofing and
the implementation of flood warning systems for extreme weather
events leading to extreme values of sea level. This strategy also
consists of land-use planning adaptations to reduce the flood risk and
the development of new insurance programs. It also includes flood-
resistant agriculture using plants that tolerate high levels of salinity.
Accommodation favors flexibility and evaluation of the adaptation
measures, while taking account both of uncertainties and additional
future information on the evolution of vulnerabilities.
Retreat is a strategy for managing shoreline setbacks and
realignment and the inland migration of coastal ecosystems to make
them less vulnerable to erosion and to the rise in GMSL. For human
systems and more specifically for the human occupation of the coastal
zone, retreat is an extreme strategy that applies only when all the other
options become impossible.
Nevertheless, it is very probable that there will be climate refugees
coming from very vulnerable coastal zones and that their number will
increase significantly in the future [UNE 11]. A current example is
taking place on the Carteret Atoll, a group of six small islands
belonging to Papua-New-Guinea, with a maximum elevation of 1.5 m