17.2.3. Beach and Coastal Changes
The morphology, characteristics, and classification of beaches are influenced
by a variety of factors, including island origin, geologic structure and composition
(e.g., volcanic, coral atoll, raised atoll, reef island, or emergent limestone),
age, elevation, and size (Gillie, 1997; Solomon and Forbes, 1999). Thus, given
their varied origins, a wide range of beach types and characteristics is represented
in the small island states of the Caribbean and Mediterranean Seas and the Atlantic,
Pacific, and Indian Oceans.
Coastal erosionpartly the result of anthropogenic factors such as sand
mining (Gillie, 1997; Ragoonaden, 1997) already is a problem on many islands
and evidently may be exacerbated by sea-level rise (Mimura and Nunn, 1998).
On many atolls (as in the Pacific) and low reef islands (as in the Caribbean),
carbonate beaches are maintained by sand produced from productive reefs whose
degradation already is causing accelerated beach erosion. Similarly, in the
Mediterranean Sea, where the islands are periodically susceptible to flooding
and scour from storm surges, an increase in storminess would further stress
natural and human systems located at the coast (Nicholls and Hoozemans, 1996).
The impact of the equivalent of a 1-m rise in sea level for a cumulative few
hours on the coast was observed in Singapore on 7-14 February 1974. The event
indicates clearly the vulnerability of the island's low-lying area to flooding
and coastal erosion if sea-level rise takes place (Wong, 1992).
Beach erosion rates of approximately 2-4 m yr-1, on average,
have been reported for several beaches in Trinidad and Tobago, where mean relative
sea-level rise of 8-10 mm yr-1 has been recorded by two gauges
during the past 15 years. Although beach erosion results from multiple forces,
sea-level rise is considered a contributory factor (Singh, 1997a,b). Ragoonaden
(1997) measured shoreline retreat of 2.7 m yr-1 at Flic-en-Flac (Mauritius),
and Nunn and Mimura (1997) report that the coasts of some islands in Fiji have
retreated by more than 30 m in the past 70 years. In the specific case of Viti
Levu and Taveuni, Fiji, beach erosion has been attributed to a combination of
human-induced causes (including loss of the mangrove fringe and other natural
protection) and elevated sea level, which has been rising at a rate of approximately
1-1.5 mm yr-1 since 1960 (Forbes and Solomon, 1997; Nunn and
22.214.171.124. Response, Adaptation, and Management
It is now widely accepted that strategies for adaptation to sea-level rise
tend to fall into three main categories: retreat, accommodate, and protect (Bijlsma,
1996; IPCC, 1996, 1998). Hard engineeringinvolving the construction of
groynes, seawalls, breakwaters, and bulkheadshas long been the traditional
response to coastal erosion and flooding in many small island states. Unfortunately,
this approach has not always been efficiently implemented and has even helped
to increase coastal vulnerability in some cases (Mimura and Nunn, 1998; Solomon
and Forbes, 1999). In these specific circumstances, the term "maladaptation"
(which refers to a response that does not succeed in reducing vulnerability
but increases it instead; see Chapter 18) may be applied.
Realistically, however, for some islands the application of hard solutions may
be the only practical option along well-developed coasts, where vital infrastructure
is at immediate risk.
There are other potential options available to small island states, including
enhancement and preservation of natural protection (e.g., replanting of mangroves
and protection of coral reefs), use of softer options such as artificial nourishment,
and raising the height of the ground of coastal villages (Nunn and Mimura, 1997).
Raising the height of the ground requires additional aggregate such as sand
and stone and a lot of pumping, in which many small islands are seriously deficient.
Removal of materials from "unimportant" islands to build up important
islands via sand transfer by pipes and barges has been suggested by the IPCC
(1990). Some island states may be faced with few practical options. Thus, it
might be necessary for them to lose some islands so that the entire nation is
not completely inundated (Nicholls and Mimura, 1998).
Similarly, beach nourishment may not be a practical or economical option for
many island nations because sand often is a scarce resource (Leatherman, 1997;
IPCC, 1998). Moreover, beach nourishment requires maintenance in the form of
periodic sand replenishment, sometimes every 5-10 years or less (Amadore
et al., 1996). Such a requirement could prove to be unsustainable in
small economies. In contrast, on some islands such as Singapore, where the technology
and resources are more readily available, beach fill projects (used in combination
with offshore breakwaters to form artificial headlands) is a feasible option
(Wong, 1985). As a general strategy to respond to sea-level rise, it is likely
that Singapore will focus on three main types of responses: coastal protection
for developed or heavily populated areas and reclaimed land, anti-salt-intrusion
measures for coastal reservoirs, and flood prevention measures (such as tidal
gates) for major canals (Wong 1992).
In some islands, such as those in the Caribbean, more emphasis is being placed
on the application of "precautionary" approaches, such as enforcement
of building set-backs, land-use regulations, building codes, and insurance coverage.
In addition, application of traditional, appropriate responses (e.g., building
on stilts and use of expendable, readily available indigenous building materials),
which have proven to be effective responses in many islands in the past, ought
to be more widely considered (Forbes and Solomon, 1997; Mimura and Nunn, 1998).
Given the vulnerability of many small island states to various aspects of global
change, integrated coastal management (ICM) is rapidly becoming an attractive
paradigm for planning adaptation (Bijlsma, 1996; Cicin-Sain, 1998; Nicholls
and Mimura, 1998). Furthermore, ICM can be regarded as both an anticipatory
and a predictive tool, with the capability to plan for and respond to medium-
and long-term concerns such as sea-level rise as well as short-term, present-day
needs (Nurse, 1999; Solomon and Forbes, 1999). In addition, ICM can provide
an effective framework for resolving potential conflict among competing stakeholder
interests, in a manner that is equitable to all groups. In this context, it
is noteworthy that all of the small island states that recently participated
in the U.S. Country Studies Program (i.e., Federated States of Micronesia, Samoa,
Fiji, Kiribati, Marshall Islands, Sri Lanka, and Mauritius) concluded that ICM
was the most appropriate adaptation strategy and should form an essential part
of their climate change national action plans (Huang, 1997).
Enhancing the resilience of coastal systems has been suggested (e.g., Bijlsma,
1996) as an appropriate proactive adaptive response to reduce vulnerability.
Klein and Nicholls (1998) agree that this could be a more cost-effective way
to prepare for uncertain changes such as sea-level rise, rather than relying
entirely on building traditional, more costly coastal defenses. Helmer et
al. (1996) strongly support the notion of enhancement of coastal resilience
whereby dynamic systems (e.g., dunes, lagoons, and estuaries) should be allowed
to utilize their natural capacity to grow in response to rising sea levels.
This philosophy could be applied through pilot studies in small islands. One
of the ways in which a dynamic and resilient coast can be created is by managed
retreat, based on an enforced building set-back that allows the coastline to
recede to a new line of defense, thus restoring natural coastal processes and
systems. An orderly plan to retreat could be a feasible option on larger islands
that cannot commit the resources necessary to prevent coastal land loss in the
face of rising sea levels (Leatherman, 1997).
One recommended approach to planning adaptation to sea-level rise and coastal
change involves an estimation of the costs of protecting or abandoning developed
properties. For developed coasts, West and Dowlatabadi (1999) propose that the
real economic evaluation of sea-level rise should be regarded as the difference
in utility (not just damages) with and without a sea-level rise scenario, in
which it is assumed that physical conditions (e.g., erosion and storms) and
human behavior remain constant. This is an improvement on past approaches, which
provided the estimated costs of sea-level rise on the basis of market value
of inundated land and property or the cost of structural protection.