Ocean & Coastal Management 46 (2003) 457–478
Environmental management of clastic coastal
depositional environments: inferences from an
Australian geomorphic database
Peter T. Harris*, Andrew D. Heap
Geoscience Australia, Petroleum and Marine Division, GPO Box 378, Canberra ACT 2601, Australia
Abstract
Simple, conceptual geomorphic models can assist environmental managers in making
informed decisions regarding management of the coast at continental and regional scales. This
basic information, detected from aerial photographs and/or satellite images, can be used to
ascertain the relative significance of several common environmental issues, including: sediment
trapping efficiency, turbidity, water circulation, and habitat change due to sedimentation for
different types of clastic coastal depositional environments. The classification of 780
Australian clastic coastal depositional environments based on their geomorphology is used
to derive a coastal regionalisation, comprised of a distinctive suite of environments for each
region. Because of the close link between the relative influence of waves and tides and the
geomorphology of clastic coastal depositional environments, a basic understanding of the
broad geomorphic and sedimentary characteristics by environmental managers will assist
them in ascertaining the relative significance of environmental issues in each region. The
benefit of this approach is that it provides guidance in tailoring management schemes
differently for each region, resulting in more effective and efficient treatment of these issues.
Crown Copyright r 2003 Published by Elsevier Science Ltd. All rights reserved.
1. Introduction
Our coastlines are supporting an increasing number and variety of human
activities. The coast is significant in terms of its economic, social and environmental
values, including: fisheries production, port activities, recreation, pollution cycling,
residential/commercial development and agriculture. In many countries, the coast
*Corresponding author. Tel.: +61-2-6249-9111; fax: +61-3-6249-9915.
E-mail address: [email protected] (P.T. Harris).
0964-5691/03/$ - see front matter Crown Copyright r 2003 Published by Elsevier Science Ltd. All rights
reserved.
doi:10.1016/S0964-5691(03)00018-8
458
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
has become a site for multiple, often competing, uses due to its ‘‘common property’’
status, and the effects of human activities have become preferentially located in
coastal depositional environments. In many cases, coastal management practises
targeting these activities, are reactive, ad hoc and non-integrated across all levels of
government and stakeholders (e.g. [1]), resulting in fragmented management
responses, particularly at regional and continental scales (e.g. [2]).
Successful management of clastic coastal depositional environments requires that
decisions are made based on an understanding of their characteristic physical and
biological processes and features. However, in the case of large coastal regions
containing numerous types of coastal environments, environmental managers are
typically faced with the dilemma of formulating policies and management practices
where environmental data are available for only a small number of systems. This is
particularly true in situations where continental-scale, national management policies
are required. In such cases, data that is readily obtained for different types of clastic
coastal depositional environments from easily accessible and cost-efficient methods
can provide essential basic information required to make informed management
decisions for a range of environmental issues.
The aim of this paper is to demonstrate the value of an understanding of the
geomorphology of coastal depositional environments when formulating regionalscale environmental policies and management practices based on physical and
biological processes and attributes. It is shown that a concise classification scheme
may be applied to a suite of clastic coastal depositional environments, based
only upon their gross geomorphology detected from aerial photographs and/or
satellite images. Specifically, it is demonstrated that this classification permits
basic deductions to be drawn that target particular management issues such as
sediment trapping efficiency, turbidity and water circulation, together with insights
into the susceptibility of an environment to significant habitat changes due to
sedimentation. A database of 780 Australian clastic coastal depositional environments is then used to show that it is possible to derive an assessment of these
management issues for a suite of environments, and ascertain their relative
significance at a regional scale.
2. Clastic coastal depositional environments
Clastic coastal depositional environments are defined as areas of the coast where
sediments supplied from terrestrial and/or marine sources are accumulating.
Coastlines characterised by erosional cliffs or rocky shores are not included in this
classification and they are beyond the scope of this paper. Because this study
originated as an assessment of the condition of Australian waterways [3], the clastic
coastal depositional environments considered in this paper are restricted to those
associated primarily with Holocene terrigenous sediment sources. As such, beachdune systems are not considered in this paper.
Two broad types of clastic coastal depositional environment are recognised:
(i) those that receive a large sediment supply and are actively prograding seawards
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
459
(e.g., deltas, strand plains and tidal flats), and (ii) those that receive a small sediment
supply and which exhibit geomorphic features associated with the Holocene sea level
rise and have yet to completely fill their paleo-valleys (e.g. [4]). Under conditions of
stable sea level, the existence of these types of clastic coastal depositional
environments depends on the relative quantities of terrestrial and/or marine
sediment supplied in relation to the size of the receiving basin.
The gross geomorphology of clastic coastal depositional environments is also
affected by the relative importance of waves and tides in controlling the amount,
nature, distribution and transport of sediment along the coast (Figs. 1 and 2). Large
swell waves generate significant alongshore sediment transport that produces coastparallel sedimentary features such as spits, barriers, sand bars and barrier islands. In
contrast, large tidal ranges (>4 m) and strong tidal currents generally produce coastnormal sedimentary features, including: elongate tidal sand banks, wide-mouthed
estuaries, funnel-shaped (in plan view) deltaic distributary channels, and broad
intertidal flats (Fig. 1).
Because of the close link between the geomorphology of clastic coastal
depositional environments and the relative influence of waves and tides at the coast,
it is possible to distinguish between wave-dominated coasts (characterised by wavedominated deltas, wave-dominated estuaries, strand plains and lagoons) and tidedominated coasts (characterised by tide-dominated deltas, tide-dominated estuaries
and prograding tidal flats, Fig. 1). This ‘‘geomorphic’’ approach makes it feasible to
identify and classify each clastic coastal depositional environment from aerial
photographs or satellite images (e.g. [3,5]). The gross geomorphology and
combination and arrangement of diagnostic sedimentary environments in clastic
coastal depositional environments are summarised by idealised facies models [6].
Transgressive
Increasing tidal power
Tide
Dominated
Estuary
Increasing wave power
Wave
Dom.
Est.
Lagoon
strand
plain
barrier
Linear coasts
mar. sed supply
Embayed coasts
Lobate coasts
Linear coasts with
marine sediment supply
Prograding
Delta
Tidal Flats
Strand Plain
Marsh
Mud
Sand
Fig. 1. Boyd et al. [4] diagram of coastal depositional environments.
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
s
lta
De
W-
Deltas
De
ltas
R-Deltas
River
Galloway's (1975)
ternary
delta classification
scheme
T-
460
Tide
Wave
Dominated Dominated
Estuaries Estuaries
Lagoons
Strand Plains
Wave
Tidal Flats
Tide
Fig. 2. Triangular diagram representing the occurrence of coastal depositional environments in relation to
relative wave, tide and river power. The upper triangle contains the ternary delta classification scheme
originally proposed by Galloway [10].
3. Facies models for clastic coastal depositional environments
Facies are a suite of geomorphic and sedimentary attributes that are diagnostic of
a sedimentary environment, or physical, chemical and biological processes. By
themselves, individual facies are of little interpretative value [6]. However, when used
in combination as facies models, facies successions highlight lateral and vertical
variations between different sedimentary environments. Facies models represent a
generalisation of the physical attributes for a certain type of depositional environment, where the local variations from numerous modern and ancient
examples have been ‘‘distilled away’’ to leave only the common features [6].
Because each clastic coastal depositional environment has a diagnostic geomorphology (represented by the unique combination of facies), a precise
classification can be established for each system (Fig. 1). From a management
perspective, it is important to emphasise that ‘‘facies’’ as used here are analogous to
biological ‘‘habitats’’ in most clastic coastal depositional environments (e.g. [7]), and
the two terms are used interchangeably throughout this paper. This study is
concerned with seven different types of clastic coastal depositional environments:
wave- and tide-dominated deltas, wave- and tide-dominated estuaries, strand plains,
tidal flats, and lagoons (Fig. 1).
3.1. Deltas
Deltas are defined as a coastal sedimentary protuberance (including offshore
subaqueous features) where a river empties into the sea. The formation of a delta
relies on the river supplying sediment to the coast more rapidly than can be
redistributed by waves and tides, causing seaward progradation [8]. The river is
connected to the sea by distributary channels, in which fresh water mixes with salt
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
461
water. The distributary channels are comprised wholly of modern sediment, derived
almost entirely from the catchment. Hence, the geomorphology of deltas owes
nothing to the antecedent bedrock geometry [8,9].
Galloway [10] formulated a conceptual classification scheme that included three
basic types of delta represented on a ternary diagram (top of Fig. 2). The gross
geomorphology of each delta varies as a function of relative wave/tide power (the X axis) compared with the river power (Y -axis). At the top of the ternary diagram,
where the river power and sediment supply are very large compared with the wave
and tide energy, the delta progrades seawards forming elongate levee banks which
look like a ‘‘bird’s foot’’ in plan view (Fig. 3A). The Mississippi River Delta located
in the low-wave energy, microtidal Gulf of Mexico is the classic bird’s foot delta (e.g.
[8,11]). The facies most strongly associated with bird’s-foot deltas are levee banks
colonised by halophytic vegetation (i.e., mangroves and salt marshes, Fig. 4).
With increasing tidal power, the ‘‘bird’s foot’’ shape changes to include funnelshaped distributary channels and tidal sand banks which are detached from, and
trend normal to the coast (Fig. 3B). The Fly River Delta in Papua New Guinea is a
good example of a tide-dominated delta [12,13]. In tide-dominated deltas, the
maximum tidal range and tidal current speeds occur within the distributary channels
(Fig. 3B). River power steadily decreases in a seaward direction from some
maximum value due to the reduction in hydraulic gradient, and wave power
decreases landward of the mouth because of the shallow water depths and the
blocking effect of tidal sand banks (Fig. 3B). Facies typically associated with tidedominated deltas are intertidal flats with halophytic vegetation (i.e., mangroves and
salt marshes, e.g. Woodroffe [14]) and tidal sand banks (Fig. 4).
In the case of wave-dominated deltas, sediment is arranged into coast-parallel
beach ridges, barrier bars, barrier islands and spits. The Niger delta in Africa is a
good example of this type [15,16]. The river channel is often deflected parallel to the
coast by these features and the river power remains high along the length of the river
channel until just landward of the mouth (Fig. 3C). Wave power drops off landward
of the mouth and tidal power is negligible outside of the channel mouth (Fig. 3C).
Facies typically associated with wave-dominated deltas are intertidal flats with
halophytic vegetation (i.e., mangroves and salt marshes) and wave-built beach ridges
and sandy barriers (Fig. 4).
3.2. Estuaries
From a geological perspective, estuaries are a particular category of clastic coastal
depositional environment best defined as ‘‘the seaward portion of a drowned valley
system which receives sediment from both fluvial (i.e., river) and marine sources and
which contains facies influenced by tide, wave and fluvial processes’’ ([17, p. 1132]).
This definition of an estuary is significantly different from that used by
oceanographers, which is based on the dilution and mixing of freshwater with
seawater [18]. Using this oceanographic definition, estuaries and deltas cannot be
distinguished from each other, although they behave very differently with respect to
their physical processes (see below). The literature is replete with alternative
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
462
100%
TOTAL
River
Relative
Power
Waves
Tides
0
100%
Relative
Power
0
100%
Riv
er
Tides
W
TOTAL
s
e
v
a
(F) Tidal Flats
0
TOTAL
es
Wav
Tides
1
2
3
100%
(G) Strand Plains
Tides
TOTAL
Wav
es
100%
Relative
Power
es
straight
meandering
straight
es
es
Tid Wav
(E) Wavedominated
Estuary
r
TOTAL
0
TOTAL
ve
es
Wav
Tides
Relative
Power
Ri
TOTAL
er
0
0
100%
Riv
Wav
100%
100%
TOTAL
(C) Wavedominated
Delta
Relative
Power
Relative
Power
Tides
0
(B) Tidedominated
Delta
(D) Tidedominated
Estuary
River
Relative
Power
Wav
es
(A) Bird'sfoot
Delta
Relative
Power
0
Tides
(H) Lagoon
Fig. 3. Idealised drawings of coastal depositional environments and their relative river-wave-tide power
distribution along the axis of waterways: (A) bird’s-foot delta, (B) tide-dominated delta, (C) wavedominated delta, (D) tide-dominated estuary (after Dalrymple et al. [17]), (E) wave-dominated estuary
(after Dalrymple et al. [17]), (F) tidal flats, (G) strand plain, and (H) lagoon. In ‘‘E’’, numerals refer to (1)
the bay head delta facies, (2) central muddy basin and (3) ebb-flood-tidal delta complex. The original
(transgressed) shoreline is shown in black with Holocene deposits and infilling sediments depicted by
shading. The dashed lines represent indicative bathymetric contours along the coast. Arrows indicate
evolutionary paths, as infilling of estuaries leads to the formation of a delta, and the infilling of a lagoon
leads to the formation of a strand plain. Dalrymple et al. [17] proposed that the straight-meanderingstraight morphology exhibited by fluvial channels distinguishes tide-dominated estuaries from tidedominated deltas (which have straight-only fluvial channels).
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
463
Reefs
Rocky shores
Salt Flats
Barrier System
Ebb/Flood Tidal Delta
Bayhead Delta
Central Muddy Basin
ENVIRONMENT
Tidal Sand Banks
= Weak
association
Intertidal Flats
= Some
association
Mangroves/Salt Marsh
FACIES - HABITATS
= Strong
association
Bird’s-foot Delta
Wave-Dominated Delta
Tide-Dominated Delta
Wave-Dominated Estuary
Tide-Dominated Estuary
Strand Plain
Tidal Flat
Lagoon
Fig. 4. Matrix diagram showing the 7 types of coastal depositional environment in relation to different
sedimentary facies recognised.
definitions of an ‘‘estuary’’ (e.g. [19]), but in the present study the above geological
definition of Dalrymple et al. [17] will be used. A key distinction is that estuaries
form in situations where the sediment supplied by rivers and the sea has not yet
infilled the original valley. Consequently, rocky shores and rocky reefs exposed along
the unfilled portions of the valley are common features of both wave- and tidedominated estuaries (Fig. 4). There are only two geomorphic estuarine end members:
wave-dominated and tide-dominated (Figs. 3D and E). There is no ‘‘riverdominated’’ end member because ‘‘the relative influence of the river primarily
determines the rate at which the estuary fills and does not alter the fundamental
morphology of the system’’ ([17, p. 1132]).
3.2.1. Tide-dominated estuaries
Good examples of tide-dominated estuaries include the Bay of Fundy in Canada
[20], the Bristol Channel and Thames estuaries in the UK [21] and the Gironde
estuary in France [22,23]. In tide-dominated estuaries, tidal energy reaches a peak
inside the estuary, and waves have less effect on sediment transport than tidal
currents (Fig. 3D). Total energy rises to a maximum at some point along the estuary
because the shoaling depth and converging sides of the funnel-shaped valley amplify
the advancing tidal wave [22]. Further landward, frictional dissipation of the tidal
power overcomes amplification and total energy falls to a minimum (Fig. 3D). Still
further landward total energy rises again in the relatively narrow, river-dominated
zone due to the influence of the freshwater flow. The facies distribution in tidedominated estuaries is organised into tidal sand banks [24], migrating dune fields and
upper flow regime (sand) flats [21,25], intertidal mud flats, and river sand and mud
colonised by halophytes and/or containing salt marshes ([26,27], Fig. 4).
464
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
3.2.2. Wave-dominated estuaries
Some better known examples of wave dominated estuaries are from studies in
eastern Canada [28], eastern United States [29], Australia [30] and South Africa [31].
Roy et al. [30] described the tripartite zonation of facies that is common to all wavedominated estuaries: (1) Barrier—tidal inlet—flood/ebb tidal deltas, (2) Central
basin—low energy zone, and (3) Bay head delta (Fig. 4). The relative spatial extent
of each facies varies between estuaries, depending on the relative wave/tide power
ratio, the relative marine versus river sediment supply, the inherited valley shape and
depth, and its degree of infilling.
The barrier is formed by waves supplying sediment to the coast via longshore
drift. Tidal currents form ebb and flood tidal deltas with respect to their
position (seaward or landward, respectively) to the tidal inlet [29]. A key process
affecting the form of the barrier, tidal inlet, and flood/ebb tidal deltas is the relative
balance between the tidal prism (i.e., the volume of water that enters or exits an
estuary between consecutive high tides) and wave energy [32]. Littoral drift delivers
sediment into the tidal inlet, which is dispersed by tidal currents. In some cases, the
tidal prism is so small in relation to the littoral drift rate that no inlet can be
maintained and the barrier is continuous across the estuary entrance (i.e., a blind
estuary).
The central basin, located landward of the barrier, is protected from swell waves
and inhibits amplification of the tide landward of the inlet, giving rise to a low energy
zone (Fig. 3E). Due to the low energy fine-grained sediment is able to accumulate in
the central basin. The bay head delta is formed almost exclusively of river-derived
sediment, deposited at the point where the river currents decelerate and lose energy
(Fig. 3E).
3.2.3. Tidal flats
Low-gradient wedges of tidal flat sediment are common along prograding coasts
characterised by mean spring tidal ranges >B4 m (Fig. 3F). Good examples are
known from The Wash, UK [33] and from San Sebastian Bay, Argentina [34]. They
are usually comprised of fine-grained marine sediment that has been transported
towards the coast by strong currents associated with the large tides. Waves are less
effective at transporting sediment along these coasts because the low-gradient and
shallow depth of the tidal flats dissipates wave energy and the large excursion
between high and low tide precludes waves breaking on any part of the tidal flat for
extended periods (Fig. 3F).
During the falling tide, drainage of seawater from the intertidal flats causes the
development of tidal creeks [33,34]. The banks of these creeks may be stabilised by
halophytes and/or salt marshes [35]. Large tidal creeks often contain tidal sand
banks and dunes (Fig. 4) but are distinguished from tide-dominated estuaries by the
absence of a river channel entering from the hinterland (i.e., rivers do not
supply sediment to tidal creeks) and by the fact that they are incised into wholly
marine, Holocene sediments (i.e., they contain no rocky shorelines or reefs, Figs. 3F
and 4).
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
465
3.3. Strand plains
Strand plains form where wave-induced sediment transport (littoral drift) results
in the formation of a series of coast-parallel depositional features. These may include
elongate, coast-parallel beach ridges, cheniers or barrier-islands (Fig. 3G).
3.3.1. Beach ridges
Beach ridges are semi-continuous, generally linear mounds of shelly sand
and gravel, deposited above the high tide line [36]. A sandy beach is always present
in front of the beach ridge. As marine-derived sediment accumulates along the
coast, the sequence progrades seawards leaving the coarser-grained ridges
‘‘stranded’’ within the finer-grained coastal plain (e.g. [37]). Beach ridges are formed
by the combination of large swell waves and high tides associated with storms.
Depressions between beach ridges may be connected and form a salt flat or
shallow lagoon (Fig. 3G), joined to the sea by tidal inlets that punctuate the seaward
ridges.
3.3.2. Cheniers
Cheniers are comprised of coarse-grained sediment deposited as a narrow linear
ridge above the level of high tide but separated from the shoreline by a marshy area
comprised of fine-grained sediment [38,39]. Cheniers form by reworking and erosion
of the shoreface by storm waves followed by a depositional phase that leaves a ridge
fronted by fine-grained sediment. Cyclical erosion and progradation of tidal flats
(e.g., from successive storm events associated with varying rates of sediment supply)
produces a series of parallel cheniers. Thus, grain size is a major factor
differentiating cheniers from beach ridges. However, beach ridges with wide swales
infilled by fine-grained sediment have been mistaken for cheniers, and hence
knowledge of the subsurface stratigraphy of the coastal sequence may be required for
definitive classification in many cases [40]. Due to this constraint, cheniers have not
been differentiated from beach ridges in the present study.
3.3.3. Barrier islands
Barrier islands are particularly abundant on wave-dominated coasts characterised
by relatively large ocean swell waves, abundant marine sediment (sand) supply, lowtidal ranges, and a relatively low-gradient shelf. Barrier islands form low relief,
coast-parallel offshore sediment bodies separated by narrow tidal inlets that are
usually backed by a relatively shallow low-energy lagoon. There are a number of
alternative theories regarding the formation of barrier islands (e.g. [41–43]).
However, once the barrier island becomes sub-aerial, storm waves and aeolian
processes are responsible for their continued development.
3.4. Lagoons
Lagoons are formed along wave-dominated coasts by flooding of beach ridges
(Fig. 3G) or by the partial closure of a coastal embayment by a subaerial barrier or
466
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
bar (Fig. 3H). Lagoons are differentiated from wave-dominated estuaries by a lack
of any significant river input [4]. The complete enclosure of the embayment by the
barrier or bar may result in the formation of a (often brackish) lake. Facies in
lagoons are the same as those found in wave-dominated estuaries, with the exception
that there is no fluvial bay head delta (Fig. 4).
4. Geologic evolution of clastic coastal depositional environments
4.1. Estuaries and Lagoons
The geological evolution of transgressive clastic coastal depositional environments
is a fundamental distinguishing factor that separates them from prograding clastic
coastal depositional environments (Fig. 1). With sufficient time and under a stable
sea level and continuous sediment supply, estuaries will infill their palaeovalleys to
form deltas (indicated by the arrows in Fig. 3). Lagoons may also infill their basins
and become incorporated into prograding strand plains. Strand plains and tidal flats
are formed in association with prograding coasts, at some distance from a river (i.e.,
they receive no direct river sediment input, see Fig. 1).
4.1.1. Wave-dominated estuaries and lagoons
Wave-dominated estuaries evolve (mature) by the seaward progradation of the
bay head delta and/or landward progradation of the flood tidal delta, infilling the
central basin (Fig. 3C and E). Major controls on the rate of infilling are the rate of
sediment supplied by the river and rate of sediment supplied by waves and tides,
which is directly related to the wave climate and tidal range at the estuary mouth
[32,44]. As the central basin fills its surface area is reduced, thus allowing the river
channel to establish a more direct connection to the tidal inlet. As the system evolves
(infills) sediment transported by the river increasingly bypasses the basin and is
transported directly to the sea. Ultimately, when the central basin is completely
filled, the river discharges directly through the tidal inlet to the sea, and the system
becomes a delta. At this stage a coastal protuberance may form if the waves and tides
are unable to redistribute the sediment at a greater rate than it is deposited at the
coast. In situations where the wave energy at the mouth is relatively high, the
entrance may be blocked or greatly restricted by a barrier or bar.
Throughout the life of a lagoon, marine sediment may be transported through the
tidal inlet by tidal currents, and across the barrier by wave and wind currents, and is
deposited in the central basin. Infilling of the lagoon with marine sediment
transforms the lagoon to a prograding strand plain.
4.1.2. Tide-dominated estuaries
Evolution of tide-dominated estuaries is characterised by the expansion in surface
area of the tidal sand banks and their merging and interdigitation with the marginal
intertidal flats [21]. In macrotidal systems (i.e., those with tidal ranges >4 m), the
overall funnel-shape of the estuary is preserved during all stages of evolution, and
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
467
persists to the deltaic stage (Fig. 3B and D), as in the case of the Fly River delta in
Papua New Guinea [12].
Recognising the point at which a tide-dominated estuary evolves into a delta is not
trivial. Diagnostic of all deltas is the existence of a coastal protuberance at the point
of river input. As the system progrades seawards, the tidal sand ridges may extend
offshore from the overall trend of the coast. However, in the case of systems that are
located in a large embayment or along an irregular coast, where it is difficult to
determine any linear coastal trend, the protuberance may not be easy to distinguish.
The existence of prodeltaic mud overlying coarse-grained shelly marine sand is
diagnostic of the estuary-delta transition, but requires seismic and sediment core
information that is often not available.
Dalrymple et al. [17] proposed a diagnostic geomorphic criterion associated with
the profile of the river channel that distinguishes estuaries from deltas. Estuaries
contain a straight-meandering-straight river channel profile, which becomes straight
with the onset of the deltaic stage (Fig. 3D). The more complex river channel profile
found in estuaries is attributed to the convergence of the seaward-moving, rivertransported sediment and landward-moving, tidally transported sediment ([17], see
Fig. 3B).
5. Environmental indicators inferred from facies models
On a regional scale, the facies models for clastic coastal depositional environments
provide environmental managers with important information about the functioning
of individual systems. Specifically, the different geomorphic classes of clastic
coastal depositional environment behave generally in a predictable manner with
respect to sedimentation and oceanographic processes such as water circulation and
turbidity.
5.1. Sediment trapping efficiency
Sediment delivered into clastic coastal depositional environments may have
different fates in terms of its retention or export, depending on whether a particular
environment is progradational or transgressive (Fig. 1). This phenomenon is known
as the ‘‘trapping efficiency’’ (TE), and is calculated from the combined volume of
river and marine sediment delivered to the waterway (Qr+Qm) minus the volume of
sediment exported offshore (Qe):
TE ¼ ðQr þ Qm QeÞ=ðQr þ QmÞ 100%:
Considering that the fate of all particle-associated contaminants is linked to the
dispersal and deposition of fine-grained material [45], the management implications
of the trapping efficiency are immediately obvious.
Sediment delivered to deltas is exported from the distributary channels to the
adjacent marine environment (i.e., prodeltaic deposition) and hence the trapping
efficiency of the distributary channels is low (Fig. 5). This is essential for the channel
468
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
Type of
Coastal
Environment
Sediment
Trapping
Efficiency
Turbidity
Circulation
Habitat Change
due to
Sedimentation
Tidedominated
Delta
Low
Naturally
High
Well
Mixed
Low
Risk
Wavedominated
Delta
Low
Naturally
Low
Salt Wedge/
Partially Mixed
Low
Risk
Tidedominated
Estuary
Moderate
Naturally
High
Well
Mixed
Some
Risk
Wavedominated
Estuary
High
Naturally
Low
Salt Wedge/
Partially Mixed
High
Risk
Tidal
Flats
Low
Naturally
High
Well
Mixed
Low
Risk
Strand
Plains
Low
Naturally
Low
Negative/
Salt Wedge/
Partially Mixed
Low
Risk
High
Naturally
Low
Negative/
Well Mixed
High
Risk
Lagoon
Fig. 5. Diagram showing the 7 types of coastal depositional environment in relation to the 4 management
issues discussed in this paper: sediment trapping efficiency, turbidity, water circulation and habitat change
due to sedimentation.
to maintain a cross-sectional area that is in hydraulic equilibrium with the combined
river and tidal flows. Drainage channels of tidal flats and strand plains act only to
redistribute sediment within the coastal zone. They are, therefore, also in hydraulic
equilibrium with the channels carrying a flow volume determined by water-tide
drainage, and hence they do not act as a net sink for coastal sediment (Fig. 5).
By contrast, sediment supplied to immature lagoons and estuaries is largely
trapped in the central basin, and very little escapes offshore (i.e., Qe is small or
negligible). For lagoons, the river sediment input (Qr) is negligible, and the only
source is from the adjacent marine environment (Qm). Blind estuaries will trap 100%
of all river sediment, until such time as a flood event cuts a new inlet through the
barrier and flushes the central basin. Even these flood events may not dislodge
contaminants trapped within the accumulated and buried fine-grained sediment in
the central basin (e.g. [46]). Examples of the environmental problems associated with
poorly flushed, wave-dominated and blind estuaries are more fully discussed by Day
[31], Hodgkin and Hesp [47] and Heggie and Skyring [48].
Generally, wave-dominated estuaries have greater trapping efficiencies than tidedominated estuaries (Fig. 5). This is because the low-energy environment of the
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
469
central basin provides suitable conditions for sediment deposition and retention
(Fig. 3E). An important management consideration is that as wave-dominated
estuaries mature and the central basin fills with sediment, the trapping efficiency is
reduced due to the increased connectivity between the river channel and tidal
channel(s). Shoaling in the central basin also makes it easier for internal windgenerated waves to resuspend material from the bed (e.g. [49]). During high flows
and flood events, fine-grained sediment may bypass the central basin entirely and be
transported offshore, carried in buoyant, turbid, freshwater plumes. Gradually, with
continued infilling and increased connectivity, the estuary loses a greater percentage
of its river sediment load to the adjacent shelf, and the trapping efficiency decreases
even further. Eventually the river channel merges with the tidal inlet and all of the
river derived sediment exits the system at which point the estuary evolves into a delta
with low trapping efficiency (e.g. [50,51]).
By contrast, tide-dominated estuaries are typically highly energetic throughout
their length (Fig. 3D). Continual reworking by strong flood and ebb tidal currents
prevents significant amounts of fine-grained sediment accumulating in the
channel(s). Instead, fine-grained sediment is deposited as intertidal flats that are
spread out along the margins of the channel(s). This marginal deposition prevails
throughout the evolution of tide-dominated estuaries and does not vary significantly
with maturation. Storm events and wind-driven circulation can cause advection of
turbid estuarine water onto the adjacent shelf, causing sediment to be exported
seawards. Thus, the sediment trapping efficiency of tide-dominated estuaries is
moderate (as compared to a wave-dominated estuary of similar Qr+Qm). An
important consequence of the high-energy conditions in tide-dominated systems is
the significant recycling of large volumes of fine-grained sediment and intermixing of
river- and marine-derived sediment, resulting in the dilution of anthropogenic
contaminants (e.g. [52]).
5.2. Turbidity
The presence of strong tidal currents in tide-dominated estuaries, tidal flats and
deltas means that these systems are naturally turbid, with total suspended solids
attaining several grams per litre in some macrotidal systems (e.g. [53], Fig. 5). In
contrast, turbidity levels in wave-dominated estuaries and lagoons are naturally low
because the central basin is relatively protected from vigorous wave action and tidal
currents by the barrier. Elevated turbidity levels may be present in wave-dominated
estuaries and lagoons where wind-generated waves inside the estuary resuspend finegrained sediment from the bed of shallow central basins (e.g. [49]). Although
turbidity is naturally lower in wave-dominated deltas than in tide-dominated deltas,
elevated turbidity will obviously occur in both systems during peak river discharge
events.
A common feature of most tidally influenced estuaries and deltas (e.g. [22]) and
some wave-dominated estuaries (e.g. [54]) is a ‘‘turbidity maximum’’. This is a
naturally occurring phenomenon and should not be confused for elevated turbidity
levels associated with anthropogenic increases in sediment runoff. In systems that
470
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
contain turbidity maxima (e.g. [55]), deformation of the tidal wave as it propagates
landward causes a shorter, but stronger flood tide current that achieves a greater
competency in transporting sediment than the weaker, but longer ebb tide current,
and hence there is a net landward transport of sediment. This process persists
landwards from the mouth until a location is reached where the seaward-flowing
river flow counterbalances the tidal asymmetry. This is the location of the estuary
turbidity maximum [22].
Increased levels of turbidity in clastic coastal depositional environments are an
important water quality issue for environmental managers because of the limitations
they present for normal photosynthesis and the impacts this has on seagrass habitat
and phytoplankton viability (e.g. [56]). The turbid water is also aesthetically
displeasing. Whereas turbidity can be used as a water quality indicator in coastal
waters that are normally ‘‘clear’’, it is not a useful measure in systems that have
naturally high turbidity levels. With this knowledge, established from the
geomorphic classification, a decision as to the appropriateness of turbidity as a
health status criterion for any clastic coastal depositional environment can be
quickly ascertained. For example, persistent, relatively high turbidity levels in a
deep-water, wave-dominated estuary might be an indicator of anthropogenic impact
such as catchment clearing (e.g. [57,58]).
5.3. Water circulation
Each type of clastic coastal depositional environment has a characteristic water
circulation pattern that is produced by the mixing of freshwater by wave and tidal
processes. Wave-dominated estuaries and wave-dominated deltas are typically
characterised by stratified, partially mixed or salt-wedge circulation because the
barrier-tidal inlet system restricts significant mixing of the fresh and saltwater masses
[59]. However, coastal waterways located in hot, arid regions where evaporation
rates exceed precipitation and runoff may possess negative (reverse) circulation
patterns, in which dense, saltier bottom water flows seawards and is replaced by
fresher, surface ocean water (e.g. [60,48]). Because of high-energy conditions, tidedominated estuaries and deltas tend to be well mixed. Tidal flats, strand plains and
lagoons do not receive any significant river input, hence tidal creeks and lagoons are
also prone to negative circulation in hot, dry climate zones.
The circulation pattern is a crucial factor governing water quality in clastic coastal
depositional environments. More importantly, the mixing rate and flushing efficiency
are important management considerations, because they are related to a system’s
susceptibility to contaminants received from the catchment (e.g. [48]). The capacity
of a system to reduce the detrimental effects of introduced contaminants is directly
related to the energy available to disperse and dilute them. Hence, more energetic,
well-mixed, tide-dominated systems are better able to disperse and dilute introduced
contaminants than low energy, stratified, wave-dominated systems. Since many
contaminants are associated with fine-grained sediment [45], the principal sinks for
the contaminants will be the central basin in wave-dominated estuaries and lagoons,
and the intertidal flats in tide-dominated estuaries and deltas.
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
471
5.4. Habitat change due to sedimentation
Sedimentation in clastic coastal depositional environments may result in two quite
different changes in habitats, depending on whether a particular environment is
prograding or transgressive in nature (Fig. 1). Sedimentation along prograding
coasts merely results in the seaward translation of facies as the entire succession
advances seawards into the marine basin.
However, along transgressive coasts, continued sedimentation results in a change
in the configuration of habitats in clastic coastal depositional environments as
sediment is deposited in the receiving basin (Fig. 3). Since the end of the Holocene
sea level rise, when incised valleys and embayments had their maximum volume, all
wave- and tide-dominated estuaries and lagoons have infilled to some extent. As the
estuary matures, the configuration of the habitats will alter, with attendant reduction
in the overall diversity of habitat types [7]. Rocky shores and offshore reefs become
buried as the estuary infills. The infilling of wave-dominated estuaries and lagoons
eventually results in the loss of the central basin (Fig. 3E). Hence, these systems are
the most vulnerable to infilling and have the greatest risk of habitat changes due to
sedimentation (Fig. 5).
An important management consequence of maturation of these systems is that, as
the configuration of habitats alters towards the deltaic stage, there is a concomitant
reduction in the overall species diversity [7]. Recent mapping of habitats in
tide-dominated estuaries around Australia [3] indicates that the coarse-grained
facies (e.g., tidal sand banks) typically move offshore during late stage maturity.
Thus, it is inferred that these systems have some risk to habitat change due to
sedimentation.
6. Application: case study from Australia
A database containing physical information for 780 Australian coastal waterways
was created by Bucher and Saenger [61,62] and later updated and modified by Digby
et al. [63]. The most recent version of this database (now known as the Australian
Estuarine Database, AED) was produced by Geoscience Australia and includes
information on over 1000 coastal waterways that may be accessed over the Internet
(http://www.ozestuaries.org). The AED includes an independent assessment of the
geomorphology of 780 clastic coastal depositional environments undertaken by
Heap et al. [3] via a visual inspection of aerial photographs, LANDSAT TM images,
maps, and nautical charts (see acknowledgements). Each waterway was classified,
using the principles of Boyd et al. [4] and Dalrymple et al. [17], as wave- or tidedominated estuaries, wave- or tide-dominated deltas, lagoons, strand plains, tidal
flats or lagoons (Fig. 1). Only the visible geomorphology was used to determine the
classification [3].
In total, 721 clastic coastal depositional environments were identified with 59
‘‘mixed/other’’ classes (e.g., embayments). Of the 721 clastic coastal depositional
environments, tidal flats are the most common (n ¼ 273), followed by
Wave-estuary
145
Wave-delta
81
Strand plain
43
Tide-estuary
99
Tide-delta
69
Tidal flats
273
Lagoon
11
Trapping efficiency
Turbidity
Circulation
Habitat change
114 (79%)
27 (33%)
9 (21%)
2 (2%)
0
12 (4%)
8 (73%)
High
Naturally low
Stratified (negative)
High risk
Total number Southeast Coast
18 (12%)
1 (1%)
0
0
0
0
1 (9%)
High
Naturally low
Stratified (negative)
High risk
Southwest Coast
0
4 (5%)
4 (9%)
51 (52%)
11 (16%)
95 (35%)
1 (9%)
Low to moderate
Naturally high
Well mixed
Moderate to low risk
Northwest Coast
Table 1
Number (and percentage) of coastal depositional environments listed by geographical area
7 (5%)
14 (17%)
21 (49%)
17 (17%)
24 (35%)
80 (29%)
1 (9%)
Low
Low to high
Both mixed and stratified
Generally low risk
6 (4%)
35 (43%)
9 (21%)
29 (29%)
34 (49%)
86 (32%)
0
Low
Low to high
Both mixed and stratified
Generally low risk
Gulf of Carpentaria Coast Northeast Coast
472
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
473
t
as
o
tC
rt
No
st
ea
rth
No
Gulf of
Carpentaria
s
e
hw
Co
t
as
Desert or no drainage to the sea
t
as
Co
st
t
ea
ut
Tide-dominated deltas
Tide-dominated estuaries
Tidal flats
Wave-dominated deltas
Wave-dominated estuaries
Strand Plains
Lagoons
he
as
uth
as
Co
So
tC
oa
So
st
we
uth
So
MurrayDarling
Great
Australian
Bight
st
Fig. 6. Distribution of 721 different coastal depositional environments around Australia, based on the
interpretation of air photographs and LANDSAT imagery. The 59 ‘‘mixed/other’’ coastal environments
are not shown. Five regions are identified, based on the distribution of coastal depositional environments,
each having a unique set of basic management guidelines (see also Table 1).
wave-dominated estuaries (n ¼ 145), tide-dominated estuaries (n ¼ 99), wavedominated deltas (n ¼ 81), tide-dominated deltas (n ¼ 69), strand plains (n ¼ 43)
and lagoons (n ¼ 11; see Table 1).
The spatial distribution of these 721 environments around the coast exhibits a
distinct zonation, such that five major coastal regions can be identified: southeast
coast, southwest coast, northwest coast, Gulf of Carpentaria coast, and northeast
coast (Fig. 6, Table 1). The southeast and southwest coasts are wave-dominated
environments, whereas the northern coastal areas (northwest, Carpentaria and
northeast) are mainly tide-dominated (Figs. 2 and 3). Although wave-dominated
estuaries occur almost exclusively in the southeast and southwest, wave-dominated
deltas and strand plains are widely scattered across the southeast, northeast, Gulf of
Carpentaria and to a lesser extent in the northwest (Fig. 6).
474
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
From this analysis, it is possible to make some generalisations about the sediment
trapping efficiency, turbidity, water circulation, and habitat change due to
sedimentation related to the seven types of clastic coastal depositional environments
(Fig. 5). Since the southeast and southwest coasts of Australia are characterised by
mainly wave-dominated estuaries ([5,47,64], Table 1), it is implied that these coasts
have relatively high sediment trapping efficiencies with naturally low turbidity levels.
The conceptual facies model implies that water circulation within the coastal
waterways of these regions is mainly stratified, with negative (saline water)
circulation occurring locally during times of very low precipitation and high
evaporation. It is further implied that coastal waterways along these coasts are at a
high risk of habitat change due to increased sedimentation.
The northwest coast of Australia (Fig. 6) is characterised mainly by
tide-dominated estuaries [65] and prograding tidal flats, with only a few deltas
([66], Table 1). Therefore, the overall trapping efficiency is moderate to low in this
region. Since the clastic coastal depositional environments along this coast are all
strongly tidally dominated, it is inferred that turbidity levels are naturally high and
that water circulation is generally well mixed (Fig. 5). The risk of habitat change due
to sedimentation is moderate to low, reflecting the generally stable geomorphic
configurations of tide-dominated estuaries and tidal flats, respectively.
The Gulf of Carpentaria coast contains a broad mixture of clastic coastal
depositional environments and hence any generalisations of their behaviour
must take into account this high degree of natural variability. It is evident that
prograding depositional environments (deltas, strand plains and tidal flats) dominate
[40,67,68]), and hence the overall sediment trapping efficiency of the coastal
waterways is inferred to be low. The progradational nature of the coast implies that
the risk of habitat changes due to sedimentation is low. Tide-dominated
environments are slightly more abundant than wave-dominated environments and
hence it is inferred that the overall turbidity of coastal waterways might be expected
to be relatively high, but occurring over a wide range. Similarly, the coastal
waterways in this region are usually generally well mixed, with some systems
exhibiting stratification and possibly negative (saline) circulation, particularly
wave-dominated estuaries during periods of very low river runoff and high
evaporation.
The northeast coast of Australia also contains a broad mixture of clastic coastal
depositional environments. Consequently, their response to sedimentation and
evolutionary behaviour on a regional scale will exhibit a high degree of variability. It
is evident that prograding depositional environments (deltas, strand plains and tidal
flats) dominate, but there are also a large number of tide-dominated estuaries
(n ¼ 29; e.g. [69]) and hence the overall sediment trapping efficiency of the coastal
waterways is inferred to be low to moderate (see also [70]). The progradational
nature of this region implies that the risk of habitat changes due to sedimentation is
generally low. Tide-dominated environments are slightly more abundant than wavedominated environments and hence it is inferred that the overall turbidity of coastal
waterways might be expected to be relatively high. The high proportion of
wave-dominated deltas in this region (43%), however, would be expected to result in
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
475
a region consisting of many systems with naturally low turbidity levels. Due to the
strong tidal influence in the region, it is inferred that the coastal waterways are
generally well mixed, although the wave-dominated deltas are likely to be stratified
during periods of very low river runoff.
7. Summary and conclusions
Clastic coastal depositional environments, defined on a geomorphic basis, are
associated with important environmental processes that are relevant for environmental management. Prograding coastlines characterised by deltas, strand plains and
tidal flats, export most of their sediment loads to the sea and have a generally low
sediment trapping efficiency. They contain a suite of habitats that will not be
significantly affected by sedimentation. In contrast, transgressive coastlines
characterised by estuaries and lagoons have a high sediment trapping efficiency.
They are, therefore, more susceptible to the accumulation of particle-associated
contaminants such as heavy metals. They also contain a suite of habitats that will
change (evolve) as they infill with sediments, and are therefore more susceptible to
catchment perturbations that affect river sediment loads.
The water contained in tide-dominated deltaic distributary channels, tidedominated estuaries and creeks that drain intertidal flats is naturally turbid and
generally well mixed. In contrast, water contained in wave-dominated deltaic
distributary channels, wave-dominated estuaries and lagoons is naturally clear (low
turbidity) and exhibits mainly stratified (estuarine) circulation patterns. In Australia,
where river run off is generally low by global standards, this circulation is often of
the inverse (negative) type, driven by high evaporation rates. From a management
perspective, therefore, human activities that give rise to higher turbidity levels are
likely to have a greater impact in wave-dominated systems (that are naturally clear)
than in tide-dominated systems (that are naturally turbid).
An assessment of 780 Australian clastic coastal depositional environments allows
for a coastal regionalisation, with management guidelines being identified for each
region. The same approach (of using a database of coastal environments) could be
applied to any region on earth where clastic coastal depositional environments may
be identified from remotely sensed imagery.
Acknowledgements
The authors are grateful for the financial support of the National Land and Water
Resources Audit for this work. We thank Dr. David Heggie, Dr. Brendon Brooke
and David Ryan of Geoscience Australia for their insightful comments on an earlier
version of the manuscript. Line drawing maps of all 780 Australian waterways [61]
can be viewed at: www.ea.gov.au/coasts/information/reports/estuaries/index.html.
This manuscript is a contribution of the Cooperative Research Centre for Coastal
476
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
Zone Management and is published with permission of the Executive Director,
Geoscience Australia.
References
[1] Cicin-Sain B, Knecht RW, Jang D, Fisk GW. Integrated coastal and ocean management: concepts
and practices. Washington, DC: Island Press, 1998. 517pp.
[2] Smith TF, Sant M, Thom B. Australian Estuaries: A framework for management. Cooperative Research Centre for Coastal Zone, Estuary and Waterway Management, Brisbane, 2001. 62pp.
[3] Heap A, Bryce S, Ryan D, Radke L, Smith C, Smith R, Harris P, Heggie D. Australian Estuaries &
Coastal Waterways: A Geoscience Perspective for Improved and Integrated Resource Management,
A Report to the National Land & Water Resources Audit Theme 7: Ecosystem Health (Record No.
2001/7). Australian Geological Survey Organisation, Canberra, 2001. 118pp.
[4] Boyd R, Dalrymple R, Zaitlin BA. Classification of clastic coastal depositional environments.
Sedimentary Geology 1992;80:139–50.
[5] Harris PT, Heap AD, Bryce SM, Porter-Smith R, Ryan DA, Heggie DT. Classification of Australian
clastic coastal depositional environments based upon a quantitative analysis of wave, tide and river
power. Journal of Sedimentary Research 2002;72(6):858–70.
[6] Walker RG, James NP. Facies models: response to sea level change. Geological Association of
Canada, St Johns, Newfoundland, 1992. 409pp.
[7] Roy PS, Williams RJ, Jones AR, Yassini I, Gibbs PJ, Coates B, West RJ, Scanes PR, Hudson JP,
Nichol S. Structure and function of south-east Australian estuaries. Estuarine Coastal and Shelf
Science 2001;53:351–84.
[8] Wright LD. River deltas. In: Davis RA, editor. Coastal sedimentary environments. New York:
Springer, 1985. p. 1–76.
[9] Reineck HE, Singh IB. Depositional sedimentary environments. Berlin: Springer, 1980. 549pp.
[10] Galloway WE. Process framework for describing the morphologic and stratigraphic evolution of
deltaic depositional systems. In: Broussard ML, editor. Deltas, models for exploration. Houston, TX:
Houston Geological Society, 1975. p. 87–98.
[11] Walker ND, Rouse Jr. LJ, Fargion GS, Biggs DC. The Great Flood of Summer 1993: Mississippi
River discharge studied. Earth in Space 1994;7(3):11–4.
[12] Harris PT, Baker EK, Cole AR, Short SA. A preliminary study of sedimentation in the tidally
dominated Fly River Delta, Gulf of Papua. Continental Shelf Research 1993;13:441–72.
[13] Dalrymple RW, Baker EK, Harris PT, Hughes MG. Sedimentology and stratigraphy of a tidedominated, foreland-basin delta (Fly River, Papua New Guinea). In: Sidi FH, Posamentier HW,
Darman H, Nummedal D, Imbert P, editors. Deltas of southeast Asia and vicinity—sedimentology,
stratigraphy, and petroleum geology. SEPM Special Publication, Tulsa, in press.
[14] Woodroffe CD. Mangrove sediments and geomorphology. In: Alongi D, Robertson A, editors.
Tropical mangrove ecosystems. Washington, DC: American Geophysical Union, 1992. p. 7–41.
[15] Allen JRL. Coastal geomorphology of eastern Nigeria: Beachridge Barrier Islands and vegetated tidal
flats. Geologie en Mijnbouw 1965;44:1–21.
[16] Oomkens E. Lithofacies relations in the Late Quaternary Niger delta complex. Sedimentology
1974;21:195–222.
[17] Dalrymple RW, Zaitlin BA, Boyd R. Estuarine facies models: conceptual basis and stratigraphic
implications. Journal of Sedimentary Petrology 1992;62:1130–46.
[18] Pritchard DW. Observation of circulation in coastal plain estuaries. In: Lauff GH, editor. Estuaries.
Washington, DC: American Association for the Advancement of Science, 1967. p. 3–5.
[19] Perillo GME. Definitions and geomorphologic classifications of estuaries. In: Perillo GME, editor.
Geomorphology and sedimentology of estuaries. Amsterdam: Elsevier, 1995. p. 17–47.
[20] Dalrymple RW, Knight RJ, Zaitlin BA, Middleton GV. Dynamics and facies model of a macrotidal
sand-bar complex Cobequid Bay-Salmon River Estuary (Bay of Fundy). Sedimentology 1990;37:
577–612.
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
477
[21] Harris PT. Large scale bedforms as indicators of mutually evasive sand transport and the sequential
infilling of wide-mouthed estuaries. Sedimentary Geology 1988;57:273–98.
[22] Allen GP, Salmon JC, Bassoulet Y, Du Penhoat Y, De Grandpre C. Effects of tides on mixing and
suspended sediment transport in macrotidal estuaries. Sedimentary Geology 1980;26:69–90.
[23] Mallet C, Howa HL, Garlan T, Sottolichio A, Hir PL. Residual transport model in correlation with
sedimentary dynamics over an elongate tidal sandbar in the Gironde Estuary (Southwestern France).
Journal of Sedimentary Research 2000;70(5):1003–16.
[24] Harris PT, Pattiaratchi CB, Cole AR, Keene JB. Evolution of subtidal sandbanks in Moreton Bay,
Eastern Australia. Marine Geology 1992;103:225–57.
[25] Dalrymple RW, Rhodes RN. Estuarine dunes and bars. In: Perillo GME, editor. Geomorphology
and sedimentology of estuaries. Amsterdam: Elsevier, 1995. p. 359–422.
[26] Belperio AD, Hails JR, Gostin VA, Polach HA. The stratigraphy of coastal carbonate banks and
Holocene sealevels of Northern Spencer Gulf, South Australia. Marine Geology 1984;61:297–313.
[27] Frey RW, Basan PB. Coastal salt marshes. In: Davis RA, editor. Coastal sedimentary environments.
New York: Springer, 1985. p. 225–301.
[28] Reinson GE. Tidal current control of submarine morphology at the mouth of the Miramichi estuary,
New Brunswick. Canadian Journal of Earth Sciences 1977;14:2524–32.
[29] Boothroyd JD. Tidal inlets and tidal deltas. In: Davis RA, editor. Coastal sedimentary environments.
New York: Springer, 1985. p. 445–532.
[30] Roy PS, Thom BG, Wright LD. Holocene sequences on an embayed high-energy coast: an
evolutionary model. Sedimentary Geology 1980;26:1–19.
[31] Day JH. The nature, origin and classification of estuaries. In: Day JH, editor. Estuarine ecology with
particular reference to South Africa. Rotterdam: Balkema, 1981. p. 1–6.
[32] Roy PS, Cowell PJ, Ferland MA, Thom BG. Wave-dominated coasts. In: Carter RWG, Woodroffe
CD, editors. Coastal evolution: Late Quaternary Shoreline morphodynamics. Cambridge: Cambridge
University Press, 1995. p. 121–86.
[33] Collins MB, Amos CL, Evans G. Observations of some sediment-transport processes over intertidal
flats, the Wash, UK. Special Publications, International Association of Sedimentology 1981;5:81–98.
[34] Vilas F, Arche A, Ferrero M, Isla F. Subantarctic macrotidal flats, cheniers and beaches in San
Sebastian Bay, Tierra Del Fuego, Argentina. Marine Geology 1999;160:301–26.
[35] Jennings JN, Coventry RJ. Structure and texture of a gravelly barrier island in the Fitzroy Estuary,
Western Australia, and the role of mangroves in the shore dynamics. Marine Geology 1973;15:
145–67.
[36] Otvos EG. Beach ridges: definition and significance. Geomorphology 2000;32:83–108.
[37] Short AD, Buckley RC, Fotheringham DG. Preliminary investigations of beach ridge progradation
on Eyre Peninsula and Kangaroo Island. Transactions of the Royal Society of South Australia
1989;113:145–61.
[38] Lees BG. The development of a chenier sequence on the Victoria Delta, Joseph Bonaparte Gulf,
northern Australia. Marine Geology 1992;103:215–24.
[39] Woodroffe CD, Grime D. Storm impact and evolution of a mangrove-fringed chenier plain, Shoal
Bay, Darwin, Australia. Marine Geology 1999;159:303–21.
[40] Rhodes EG. Depositional model for a chenier plain, Gulf of Carpentaria. Sedimentology
1982;29:201–21.
[41] Otvos EG. Development and migration of barrier-islands, northern Gulf of Mexico. Geological
Society of America Bulletin 1970;81:241–6.
[42] Davis RA, editor. Geology of Holocene barrier island systems. Berlin: Springer, 1995. p. 1–46.
[43] Leeder MR. Sedimentology, sedimentary basins: from turbulence to tectonics. Oxford: Blackwell,
1999. 592pp.
[44] Borrego J, Morales JA, Pendon JG. Holocene estuarine facies along the mesotidal coast of Huelva,
southwestern Spain. In: Flemming BW, Bartholoma A, editors. Tidal signatures in modern and
ancient sediments. Oxford: Blackwell, 1995. p. 151–70.
[45] Horowitz AJ. A primer on sediment-trace element chemistry, 2nd ed. Chelsea: Lewis Publishers, 1991.
136pp.
478
P.T. Harris, A.D. Heap / Ocean & Coastal Management 46 (2003) 457–478
[46] McKee LJ, Eyre BD, Hossain S. Transport and retention of nitrogen and phosphorus in the subtropical Richmond River estuary, Australia; a budget approach. Biogeochemistry 2000;50:241–78.
[47] Hodgkin EP, Hesp P. Estuaries to salt lakes: Holocene transformation of the estuarine ecosystems of
southwestern Australia. Marine and Freshwater Research 1998;49:183–201.
[48] Heggie DT, Skyring GW. Flushing of Australian estuaries, coastal lakes and embayments: an
overview with biogeochemical commentary. AGSO Journal of the Australian Geology and
Geophysics 1999;17:211–25.
[49] Green MO, Black KP, Amos CL. Control of estuarine sediment dynamics by interactions between
currents and waves at several scales. Marine Geology 1997;144:97–116.
[50] Elliott T. Deltas. In: Reading HG, editor. Sedimentary environments and facies. Oxford: Blackwell
Scientific Publications, 1986. p. 113–54.
[51] Woolfe KJ, Larcombe P, Stewart LK. Shelf sediments adjacent to the Herbert River Delta, Great
Barrier Reef, Australia. Australian Journal of Earth Sciences 2000;47:301–8.
[52] Baker EK. Sedimentation in a tidally dominated delta and the impact of upstream mining: Fly River,
Papua New Guinea. Unpublished PhD Thesis, University of Sydney, 1999. 244pp.
[53] Collins MB. Sediment transport in the Bristol Channel: a review. Proceedings of the Geologists
Association 1987;98:367–83.
[54] Hughes MG, Harris PT, Hubble TCT. Dynamics of the turbidity maximum zone in a micro-tidal
estuary: Hawkesbury River, Australia. Sedimentology 1998;45:397–410.
[55] Wolanski E, Nguyen HN, Spagnol S. Sediment dynamics during low flow conditions in the Mekong
River estuary, Vietnam. Journal of Coastal Research 1998;14:472–82.
[56] Boyer JN, Fourqurean JW, Jones RD. Seasonal and long-term trends in the water quality of Florida
Bay (1989–1997). Estuaries 1999;22:417–30.
[57] Wilber CG. Turbidity in the aquatic environment: an environmental factor in fresh and oceanic
waters. Springfield, IL: Charles C. Thomas Publishers, 1983. 127pp.
[58] Dennison WC, Abal EG. Moreton Bay study: a scientific basis for the healthy waterways campaign.
Southeast Queensland Regional Water Quality Management Strategy Team. Brisbane, 1999. 125pp.
[59] Nichols MN, Biggs RB. Estuaries. In: Davis Jr. RA, editor. Coastal sedimentary environments.
Springer: New York, 1985. p. 77–186.
[60] Nunes Vaz RA, Lennon GW, Bowers DG. Physical behaviour of a large, negative or inverse estuary.
Continental Shelf Research 1990;10:277–304.
[61] Bucher D, Saenger P. An inventory of Australian estuaries and enclosed marine waters: an overview
of results. Australian Geographical Studies 1991;29:370–81.
[62] Bucher D, Saenger PA. Classification of tropical and subtropical Australian estuaries. Aquatic
Conservation—Marine and Freshwater Ecosystems 1994;4:1–19.
[63] Digby MJ, Saenger P, Whelan MB, McConchie D, Eyre B, Holmes N, Bucher D. A physical classification
of Australian Estuaries (Report prepared for the Urban Water Research Association of Australia No.
4178). Southern Cross University, Centre for Coastal Management, Lismore, NSW, 1998. 47pp.
[64] Kench P. Geomorphology of Australian Estuaries: review and prospect. Australian Journal of
Ecology 1999;24:367–80.
[65] Wright LD, Coleman JM, Thom BG. Sediment transport and deposition in a macrotidal river
channel: Ord River, Western Australia. In: Cronin LE, editor. Estuarine research: geology and
engineering. New York: Academic Press, 1975. p. 309–22.
[66] Johnson DP. Sedimentary facies of an arid-zone delta: Gascoyne Delta, Western Australia. Journal of
Sedimentary Petrology 1982;52:547–63.
[67] Jones BG, Martin GR, Senapati N. Riverine-tidal interactions in the monsoonal Gilbert River
fandelta, northern Australia. Sedimentary Geology 1993;83:319–37.
[68] Woodroffe CD, Chappell J. Holocene emergence and evolution of the McArthur River delta,
southwestern Gulf of Carpentaria, Australia. Sedimentary Geology 1993;83:303–17.
[69] Cook PJ, Mayo W. Sedimentology and Holocene history of a tropical estuary (Broad Sound,
Queensland). Australian Bureau of Mineral Resources Bulletin 1978;170:206.
[70] Larcombe P, Woolfe KJ. Terrigenous sediments as influences upon Holocene nearshore coral reefs,
central Great Barrier Reef, Australia. Australian Journal of Earth Sciences 1999;46:141–54.