6.6.2. Resilience and Vulnerability
In the context of climate change and coastal management, vulnerability is now
a familiar concept. On the other hand, the concept of coastal resilience is
less well known but has become much more important in recent years (Box
6-5). Coastal resilience has ecological, morphological, and socioeconomic
components, each of which represents another aspect of the coastal system's
adaptive capacity to external disturbances. We have identified several natural
features that contribute to resilience of the shore-zone by providing ecological
buffers, including coral reefs, salt marsh, and mangrove forest and morphological
protection in the form of sand and gravel beaches, barriers, and coastal dunes.
Socioeconomic resilience is the capability of a society to prevent or cope
with the impacts of climate change and sea-level rise, including technical,
institutional, economic, and cultural ability (as indicated in Box
6-5). Enhancing this resilience is equivalent to reducing the risk of the
impacts on society. This resilience can be strengthened mainly by decreasing
the probability of occurrence of hazard (managed retreat or protection); avoiding
or reducing its potential effects (accommodation or protection), and facilitating
recovery from the damages when impacts occur. Among these options, managed retreat
has gained some prominence in the past 2 decades (see Box
6-6); Clark (1998) has argued that flood insurance is an appropriate management
strategy to enhance coastal resilience in the UK.
Technological capacity is a component of social and economic resilience, although
adaptation strategies may involve more than engineering measures. Technological
options can be implemented efficiently only in an appropriate economic, institutional,
legal, and sociocultural context. A list of technologies that could be effective
for adaptation appears in Klein et al. (2000). Indigenous (traditional)
technologies should be considered as an option to increase resilience and, to
be effective, must fit in with traditional social structures (Veitayaki, 1998;
Nunn et al., 1999).
Enhancing coastal resilience in these ways increasingly is regarded as an appropriate
way to prepare for uncertain future changes, while maintaining opportunities
for coastal development (although some tradeoffs are involved, and the political
discourse is challenging). In short, enhancing resilience is a potentially powerful
adaptive measure.
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Box 6-6. Adaptation through Managed Retreat
Managed retreat generally is designed to avoid hazards and prevent ecosystems
from being squeezed between development and the advancing sea. The most
common mechanisms for managed retreat are setbacks that require
new development to be a minimum distance from the shore, density restrictions
that limit development, and rolling easement policies that allow
development on the condition that it be removed to enable wetlands to
migrate landward (Titus, 1998). These strategies may all become elements
of an integrated coastal management policy. Setback could be considered
a managed retreat strategy, particularly in cases in which the setback
line is shifted inland as the shoreline recedes. Other measures of managed
retreat can include conditional phased-out development, withdrawal of
government subsidies, and denial of flood insurance.
Examples of managed retreat and related measures as adaptation to sea-level
rise include the following:
- Canada: New Brunswick completed remapping of the entire coast
of the province to delineate the landward limit of coastal features.
Setback for new development is defined from this limit. Some other provinces
have adopted a variety of setback policies, based on estimates of future
coastal retreat.
- Barbados: A national statute establishes a minimum building
setback along sandy coasts of 30 m from mean high-water mark; along
coastal cliffs the setback is 10 m from the undercut portion of the
cliff.
- Aruba and Antigua: Setback established at 50 m inland from
high-water mark.
- Sri Lanka: Setback areas and no-build zones identified
in Coastal Zone Management Plan. Minimum setbacks of 60 m from line
of mean sea level are regarded as good planning practice.
- United Kingdom: House of Commons in 1998 endorsed the concept
of managed realignment as the preferred long-term strategy for
coastal defense in some areas.
- United States: The states of Maine, Massachusetts, Rhode Island,
and South Carolina have implemented various forms of rolling easement
policies to ensure that wetlands and beaches can migrate inland as sea
level rises.
- Australia: Several states have coastal setback and minimum
elevation policies, including those to accommodate potential sea-level
rise and storm surge. In South Australia, setbacks take into account
the100-year erosional trend plus the effect of a 0.3-m sea-level rise
to 2050. Building sites should be above storm-surge flood level for
the 100-year return interval.
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6.6.3. Adaptation in the Coastal Zone
Figure 6-1: The role of adaptation in reducing potential impacts
in the coastal zone from global temperature increase and sea-level rise
to the year 2100. The bottom panel is a schematic that shows the increasing
cost or loss to an economic sector, ecosytem, or country. The area shown
by cross-hatch indicates the range of possible impacts and how net impact
can be reduced with adaptation. Stipple within the cross-hatched areas indicates
the importance of sector, ecosystem, or country resilience as a component
of net impact. |
The purpose of adaptation is to reduce the net cost of
climate change and sea-level rise, whether those costs apply to an economic
sector, an ecosystem, or a country. A simple schematic of the objective of adaptation
appears in Figure 6-1.
Adaptation within natural systems has been considered a possibility only recently;
it results in part from considerations of coastal resilience. An example is
provided by coral reefs. Applying the two types of adaptation discussed in Box
6-5, Pittock (1999) suggests that "autonomous adaptation" is what reefs
would do by themselves, whereas "planned adaptation" involves conscious human
interference to assist in the persistence of some desirable characteristics
of the coral reef system. The first type of adaptation may involve more rapid
growth of coral, changes in species composition, or evolution of particular
species in response to changed temperatures or other conditions. Planned adaptation
might involve "seeding" of particular reefs with species adapted to higher temperatures
or attempts to limit increased sediment, pollutant, or freshwater flow onto
reefs. For reef communities that presently are under stress and are likely to
be particularly vulnerable to climate change, the design of managed (or planned)
adaptation should involve an evaluation of the extent of autonomous adaptation
that can be expected given the current and probable future status of the reef
system.
Some adaptation measures handle uncertainty better than others. For example,
beach nourishment can be implemented as relative sea level rises and therefore
is more flexible than a dike or seawall; expansion of the latter may require
removal or addition of structures. Any move from "hard" (e.g., seawall)
to "soft" (e.g., beach nourishment) shore protection measures must
be accompanied, however, by a much better understanding of coastal processes
that prevail in the area (Leafe et al., 1998). Rolling easements are
more robust than setbacks (Titus, 1998) but may be impractical for market or
cultural reasons. Maddrell (1996) found that over time scales of 35 and 100
years, managed coastal retreat is the most cost-effective adaptation option
in reducing flood risks and protection costs for nuclear power facilities on
the shingle foreland at Dungeness, UK. Flood insurance can discourage a flexible
response if rates are kept artificially low or fixed at the time of initial
construction, as they are in the United States (Crowell et al., 1999).
Reevaluations of the efficacy of hard shore protection schemes as a long-term
response to climate change and sea-level rise are increasingly being undertaken.
Chao and Hobbs (1997) have considered the role of decision analysis of shore
protection under climate change uncertainty; Pope (1997) has suggested several
ways of responding to coastal erosion and flooding that have relevance in the
context of climate change. Documented changes in tidal characteristics as a
result of the construction of sea dikes and seawalls also have implications
for shore protection in the face of rising sea level. Several alternatives to
seawalls have been suggested as adaptation measures to reduce coastal erosion
and saltwater intrusion from rising sea levels in Shanghai, including improving
drainage quality and channel capacity, increasing pumping facilities to reduce
the water table, constructing a barrier across the mouth of the river, and developing
new crops that are tolerant of a higher groundwater table (Chen and Zong, 1999).
It also should be noted, however, that Doornkamp (1998) has argued that in
some situations past management decisions about human activities in the coastal
zone (including flood defenses, occupance of flood-prone lands, extraction of
groundwater and natural gas) have had an impact on relative land and sea levels
and have done more to increase the risk of coastal flooding than damage that
can be assigned to global warming to date.
