Geoscience Reference
In-Depth Information
change/geoindicators and modelling. A key con-
sideration of such studies are the relationships
between sedimentary processes and geomorpho-
logical change at different time-scales.
observed sequences of coastal morphological
measurement. Such approaches are often con-
strained by lack of sufficiently long-term data
sets to render the approach statistically valid.
Constraints on these approaches relate to the
representativeness of the data collected and its
spatial coverage. Most importantly, the effect of
storms is often missed.
8.6.2.1 Field studies
Field studies in applied coastal sedimentology
utilize a wide range of techniques including, at
the short time-scale, tracer studies of grain move-
ments, sediment traps that capture some or all of
the sediment flux at a given point and acoustic
and optical backscattering to measure sediment
concentrations. Each of these measures is usu-
ally accompanied by quantification of some ele-
ment of the dynamic environment (e.g. wave
parameters, currents) or geomorphological re-
sponse (e.g. bed-level changes), and relationships
are sought between dynamics and sediment
transport. Over longer time-scales, repeat field
measurement of beach profiles, nearshore topo-
graphy or other elements of the coastal morpho-
logy are used to assess sedimentary behaviour
over time. These too are often accompanied by
measures of dynamic data or proxy dynamic
data, usually at longer time-scales than those
utilized in short-term studies. Recognition of
the lack of a direct relationship between short
and medium-term data hampers the integration
of data gathered using these approaches (Carter
& Woodroffe 1994).
As field data reflect a range of local variables
(textural, inherited factors and dynamics), their
generic applicability remains to be tested (Cooper
& Pilkey 2004a). A range of analytical tech-
niques (visual, statistical, mathematical) are used
to test for relationships between sedimentary/
morphological factors and dynamics (e.g. Clarke
& Eliot 1988). Unfortunately, the results of field
studies are often viewed as universal and empir-
ical relationships are applied elsewhere without
due consideration of their limitations (Cooper
& Pilkey 2004b). Faced with the difficulty of
relating empirical measurements of coastal change
to measurements of forcing factors, ever more
elaborate approaches have been developed. These
include neural networks (Chen et al. 1990), which
seek patterns in non-linear systems including
8.6.2.2 Historical change and geoindicators
A range of indicators of coastal morphological
change is available for most coastlines. These
are variable in quality and temporal/spatial
coverage. Using long data sets of beach change
and storminess, Bryant (1988) ascribed changes
in high-tide morphological state to a combina-
tion of rainfall, storminess, air circulation and
sea-level change. The Dutch beach nourishment
approach (Verhagen 1992) involves initially
obtaining and analysing a decadal record of weekly
beach profiles on the beach to be nourished. The
assumption is made that the nourished beach
will behave more or less like the natural beach.
In the field, a range of indicators exist including
sediment accumulation against groynes, rates of
inlet movement, etc. (Bush et al. 1996). On many
beaches, the presence of groynes, jetties, fishing
piers, erosion debris, seawalls and other engineer-
ing projects provides geoindicators. Constraints
on the historical approach relate to the availabil-
ity of data, the extent to which coastal behaviour
is captured by a series of snapshots, and whether
accompanying dynamic data exist to aid inter-
pretation of the morphological information.
8.6.2.3 Modelling
Modelling of coastal processes is a widespread
approach in contemporary coastal management.
Models fall into two categories: (i) research
models and (ii) applied or practical models
(Davies & Villaret 2002). Differences between
the two are discussed by Thieler et al. (2000).
Research models serve the purpose of investigat-
ing the mechanisms of sediment transport in
the coastal zone and can yield important new
discoveries regarding the role of interacting waves
