Geoscience Reference
In-Depth Information
In Cyprus, much of the coastline relies on fluvial
sediment supply for its main source of sediment.
Owing to increased population and tourist num-
bers, freshwater storage capacity increased from
6 million cubic metres to 297 million cubic metres
between 1960 and 1988 (Smith & Marchand
2001). This has been achieved through increased
reservoir construction and the building of dams.
The result is that little sediment now reaches
the island's estuaries, resulting in beach erosion
along some coasts of up to 0.5 m yr
−1
, ironically
destroying the resource necessary for sustain-
ing the tourist industry. The significance of this
increased demand for fresh water cannot be
underestimated. Aquifers and rivers are the prime
sources of such water and increased extraction
in both, but particularly rivers, will have key
impacts in estuaries and deltas. The Nile delta
(Case Study 7.2) is a good example, where
important lessons should be learnt.
One further future issue to threaten estuaries
in particular lies in the method being increas-
ingly used to mediate against intertidal loss as
a result of sea-level rise. Managed realignment
is increasingly being seen as a way to increase
the intertidal volume of an estuary, yet there
are many unknowns about this technique that
need to be investigated. As a comparatively new
approach to coastal management, its increased
usage has occurred against a background of little
firm knowledge of the longer-term impacts and
a range of issues have arisen from early uses of
the method. Most notable appears to be the role
of pre-realignment vegetation on a site. Because
vegetation is effective in enhancing the trapping
of sediment on developing marsh surfaces, its
presence can be seen as beneficial (Stoddart et al.
1989; Fig. 7.6). In some examples of realign-
ment, however, vegetation has not served this
function but has decayed following rapid burial
(Macleod et al. 1999). This decay has led to
the generation of anoxic conditions, which have
actually delayed marsh initiation. Other factors
include: larger scale changes in soil properties,
often governed by what has happened in terms
of improvement during its agricultural history;
the change in groundwater dynamics, leading
to the release of stored contaminants; and gen-
eral changes in ground water levels and salinity
(Boorman & Hazeldon 1995; Crooks et al. 2002;
Blackwell et al. 2004). Overall, the message here
is that although realignment presents a logical
and sound approach to increasing estuarine
marsh loss, there are important lessons still to be
learnt. Some of these can be informed from
existing schemes, and some from looking at
historic storm-breached sites. Overall, however,
there are still major questions to be answered,
with much of the required knowledge having
to come from existing realignment sites.
Much of what has been written has been pre-
dicated by a presumption that scientists under-
stand deltas and estuaries. In some areas of
knowledge, this is the case, but in others, the
ability to predict what may happen in the future
is based on a poor understanding of the principles
and functioning of these highly dynamic systems.
The bottom line is that although we can measure
and attempt to understand how estuaries work
now, our ability to predict change is still restricted.
Perhaps the key issue here is that estuaries and
deltas are complex systems that contain a range
of linking processes combining aspects of geo-
morphology, sedimentology and ecology, as well
as human influences. One essential issue for the
future, therefore, is to manage the whole system
as an entity with a range of component parts,
and not to manage the component parts individ-
ually. The ecosystem approach to management
is a philosophy that is gaining popularity across
a range of systems. By combining population
dynamics with nutrient and sediment cycling,
ecological production, sediment and water move-
ments, and anthropogenic usage, management
can be made much more effective. Mann (2000),
however, reported that at the time of his writing
efforts to produce predictive models of coastal
ecosystems, such as estuarine and delta systems,
have had limited success. One of the key issues
here is the lack of adequate data sets to allow
models of the complexity of estuarine interac-
tions to be developed, and a second is to develop
such a model that can cope with the spatial and
temporal dynamics necessary.
