Geomorphology and Sedimentology of Estuaries

470 Pages·1995·10.928 MB·1-471\470

by  G.M.E. Perillo (Eds.)

PREFACE
In the Solar System there is a strange planet that occupies the third position from
the Sun. It is the only planet in the system that has liquid water covering about
three-quarters of its surface. The planet is so strange that even its name is reversed,
instead of being named Oceanus, it was named after a minor characteristic: Earth.
Although dynamic processes over the oceans and continents of this planet are
strong, there is nothing to compare with the energy of the interaction between the
atmosphere, the sea and the continent at the area of contact between the latter two.
The coastal zone, tremendously dynamic, is where forces are continuously changing
in an abrupt fashion, depending on the local and also the distant climatic conditions.
Storms that ram the deep ocean produce waves that a few days later impinge beaches
located several thousand kilometres away. In general, these swells help to build up
the beach by transporting sand ashore. Waves generated by storms at or near to the
shore tend to be destructive to the beach, moving sand seaward. In any case, littoral
transport is important in developing spits, barriers and other morphological features
that tend to close embayments, modifying inlets and redistributing the sediment
introduced by the rivers.
Inland precipitation (either rain or snow) is the actual source of river water that
follows the river valley until it finally debouches into the ocean. Normally, higher
river discharges are associated with larger sediment transport (the converse is also
true). This sediment is deposited at the river mouth forming a coastal plain that
contains (or not) a delta, or on the adjoining continental shelf, or, in a few cases, is
carried out directly to the abyssal plains. The larger the relative energy of the sea (as
compared with the river sediment discharge) at the coast, the higher the chances that
the sediment input by the river is redistributed along the adjacent shoreline.
As the river encounters the sea, flesh and salt water mix within the lower
river valley forming estuaries. Although the dilution of sea water is a distinctive
characteristic of estuaries, there are many other factors equally as important. For
instance, the tides are also fundamental to the development of estuaries since they
provide, in general, most of the energy to establish the mixing process of both
water masses, but also play a definitive role in establishing the morphology of the
environment and the distribution of sediments. Other factors, such as waves or
wind, render major parts in microtidal estuaries or at particular places within other
estuaries.
Practically all processes that take place in an estuary are related, at least to a
minor extent, to the general or particular shape and sediment input, output, distribu-
tion and transport. For instance, tidal wave propagation is strongly dependent on the
variations in depth and the ratio convergence/friction offered by the channel. Biota-
vi ECAFERP
sediment interactions are always present as environmental conditions and geomor-
phology are changed. Modifications in channel depth by dredging induce variations
in salt intrusion and the resulting thermohaline circulation, often defining sectors of
turbidity maxima, and sediment deposition may increase several times resulting in
the need for more dredging. Furthermore, many biological and chemical pollutants
are commonly associated with fine sediment particles transported in suspension. Par-
ticular geomorphologic settings may establish the hydrodynamic conditions to force
deposition of the contaminated particles, thus affecting the benthic fauna of the area.
The few and brief examples outlined in the previous paragraphs have been taken
from real cases occurring in different estuaries throughout the world. They are not
isolated cases, but facts that are commonly reported in the estuarine literature. All
of them are actually dependent on the geomorphology and sedimentology of the
environment. Nowadays there si a large number of books on the market dealing with
different aspects of the biology, chemistry and physical characteristics of estuaries
and processes occurring in estuaries. There also si an increasing amount of literature
describing the general processes and modelling of sediment transport. However, to
my knowledge, there si no book that specifically covers the basic geomorphology and
sedimentology of these coastal water bodies.
In textbooks and other books resulting from scientific meetings which deal with
estuarine problems, the way geomorphology affects all other processes si discussed
summarily and, on many occasions, si disregarded as a minor part. However, it si
my view that the particular shape of the environment and the constitution of its
boundaries actually play a decisive role in the outcome of any process occurring
there. Commonly, this situation arises because all processes are quite complex and
their sn0-itcar~n~n! with the boundaries are strongly nonlinear, becoming still more
difficult to model.
Therefore, the aim of the book si to provide a detailed view of the geomorphology
and sedimentology of estuaries. The matter will be presented in such a way that it
can be utilized not only by specialists of the subject, but also by other researchers
requiring the background to put their own work into an adequate perspective. The
new generation of researchers, now graduate students, will benefit from this book.
It will help them to understand that an estuary si a complex entity that cannot be
analyzed only at the level of a single science. Multi- and interdisciplinary approaches
are a must. Furthermore, an adequate knowledge of the geomorphology of estuaries
si also required for a relatively new and most needed science: coastal management.
The book si based on a new definition and morphogenetic classification. The new
definition of estuaries covers, for the first time, the basic characteristics required for
all disciplines dealing with these coastal environments. Moreover, the morphogenetic
classification actually resumes the most modern approaches provided by renown
specialists in geomorphology (e.g., Rhodes Fairbridge), plus it also introduces a
criterion that relates the degree of modifications produced by the sea. The balance
between the terrestrial and marine forces are a definitive conditioning of the resulting
morphology.
Leading experts have provided in-depth descriptions of the geomorphology, sed-
imentology and interactive processes associated with each category in individual
P REFACE vii
chapters. Their exposition si directed to present the state-of-the-art in a format
adequate for the researcher, but also of use as a textbook for graduate students.
It is also worthwhile mentioning the quality of the specialists that have accepted to
write the different chapters. This international ensemble has, in conjoint, an expertise
only paralleled a few times in other books of similar scope. Each author is active both
in research and teaching (most of them are senior researchers and/or full professors
at their respective institutions). I tried to be very careful in their selection to cover
both research and teaching aspects assuring a didactic rather than purely scientific
form of presenting the facts and examples.
The first two chapters give an introduction to the study of the geomorphology and
sedimentology of estuaries and present a review of the most common definitions and
geomorphologic classifications. Specifically in Chapter ,2 a new definition of estuaries
is introduced with an open criterion. I see this definition as a step further to finding
out a still more comprehensive definition that will arrive after we have obtained a
thorough knowledge of estuaries. Chapters 3 to 9 are devoted to the description of
the geomorphologic and sedimentologic characteristics of the elements that form the
classification on which this book is based. Chapters 01 to 31 cover major features
that are normally present in estuaries, although they are also common in open
coasts. Finally, Chapter 41 provides a review of the most common sediment transport
processes that occur in estuaries.
From the moment I first had the idea about this book until the writing of these
notes, several years have passed and many colleagues have encouraged me to con-
tinue, alongside, in particular, my wife Cintia and my children, Mauricio and Vanesa,
who put up with the long hours of work necessary for the book. My special thanks go
to the authors of each chapter who believed in the project and made special efforts
to meet the deadlines. I would also like to express my sincere gratitude to the review-
ers of the individual chapters, listed here in alphabetic order: Henry Bokuniewicz,
Diana G. Cuadrado, James M. Coleman, Clifford Embleton, G. Evans, Rhodes Fair-
bridge, Eduardo A. G6mez, .S Susana Ginsberg, John McManus, M. Cintia Piccolo,
H. Postma, Donald J.E Swift, J.J.H. Terwindt, Federico Vilas, Eric Wolanski and
another five reviewers who wished to remain anonymous. All of them contributed
profoundly, providing new insights and criteria that increased the value of each
contribution.
I would also like to thank Elsevier Science, especially Drs. Martin Tanke who
accepted the idea right from the beginning and encouraged me all the time he was
in charge of the production. Mr. Dominic Vaughan received the 'hot potato' halfway
and handled it most efficiently. Mrs. Maria Ofelia Cirone was very efficient in editing
the original manuscripts and arranging them in a unique editorial format.
Gerardo M.E. Perillo
Bahia Blanca, September 1994
viii
PREFACE
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xi
LIST OF CONTRIBUTORS
CARL L. AMOS, Geological Survey of Canada, Atlantic Geoscience Centre, Bed-
ford Institute of Oceanography, Dartmouth, Nova Scotia, B2Y 4A2 Canada
ROWLAND J. ATKINS, Hay and Co. Consultants Inc., 1 W 7th Ave., Vancouver,
British Columbia, V5Y 5L1 Canada
PIETER G.E.E AUGUSTINUS, Netherlands Centre of Coastal Research (NCK),
Institute for Marine and Atmospheric Research Utrecht, Utrecht University,
P.O. Box 08 115, 3508 TC Utrecht, The Netherlands
HENRY BOKUNIEWICZ, Marine Sciences Research Center, State University of
New York, Stony Brook, New York 11794-5000, USA
PATRICE CASTAING, D6partement de G6ologie et Oc6anographie/URA 197,
Universit6 de Bordeaux ,I Avenue des Facult6s, 33405 Talence, Cedex-France
ROBERT .W DALRYMPLE, Department of Geological Sciences, Queen's Univer-
sity, Kingston, Ontario, K7L 3N6 Canada
KEITH R. DYER, Institute of Marine Studies, University of Plymouth, Plymouth,
Devon PIA 8AA, UK
JONATHAN .W GIBSON, Department of Geography, Simon Fraser University,
Burnaby, British Columbia, VSA 651 Canada
ANDRI~ GUILCHER, D6partement de G6ographie, Universit6 de Bretagne Occi-
dentale, B.P. 814, 29285 Brest, France
BRUCE .S HART, Department of Geosciences, Pennsylvania State University,
University Park, Pennsylvania 16801, USA
FEDERICO .I ISLA, CONICET-UNMDP, Centro de Geologia de Costas y del
Cuaternario, c.c. 722, 7600 Mar del Plata, Argentina.
JOHN L. LUTERNAUER, Geological Survey of Canada, 001 W Pender St., Van-
couver, British Columbia, V6B 1R8 Canada
ANNE .I MOODY, AIM Ecological Consultants Ltd., 001 Mile House, British
Columbia, V0K 2E0 Canada
TSIL FO SROTUBIRTNOC
GERARDO M.E. PERILLO, Instituto Argentino de Oceanografia, Av. Alem ,35
8000 Bahia Blanca, Argentina, and Departamento de Geologia, Universidad
Nacional del Sur, San Juan 670, 8000 Bahia Blanca, Argentina
MARIO PINO QUIVIRA, Instituto de Geociencias, Universid~id Austral de Chile,
Casilla 567, Valdivia, Chile
ROBERT N. RHODES, COA Coastal Ocean Associates, Inc., 7 Coral Street,
Dartmouth, Nova Scotia, B2Y 2Wl Canada
JOHN SHAW, Geological Survey of Canada, Bedford Institute of Oceanography,
Dartmouth, Nova Scotia, B2Y 4A2 Canada
JAMES EM. SYVITSKI, Geological Survey of Canada Bedford Institute of Oceano-
graphy Dartmouth, Nova Scotia, B2Y 4A2 Canada
JOHN .T WELLS, Institute of Marine Sciences, University of North Carolina-
Chapel Hill, Morehead City, North Carolina 28557, USA
HARRY EL. WILLIAMS, Department of Geography, University of North Texas,
Box 5277, Denton, Texas 76203-0277, USA
Geomorphology and Sedimentology of .seirautsE Developments ni Sedimentology 35
edited by G.M.E. Perillo
© 1995 Elsevier Science B.V. All rights reserved.
Chapter 1
GEOMORPHOLOGY AND SEDIMENTOLOGY OF ESTUARIES:
AN INTRODUCTION
GERARDO M.E. PERILLO
NOITCUDORTNI
Geomorphology is concerned with the study of earth-surface forms and with their
evolution in time and space due to the physicochemical and biological factors acting
on them. Most of the evolution is the product of a cyclic process based on erosion-
transport-deposition of sediment particles. Added to this are the combinations that
may occur from the meteorization of a hard rock until the particle is permanently
buried and becomes part of a new sedimentary rock.
In particular, the coastal environments are subjected to the most energetic
conditions on the earth surface. Modifications of geoforms and the characteristics
of sediment distribution may occur in very short time periods. Nevertheless spatial
and time scales may range from few seconds and centimeters to centuries and
thousands of kilometers (Table 1-1). Estuaries are one of the most important
coastal features subject to strong processes that fully cover the space-temporal scale.
Geomorphologic and sedimentologic changes are continuously occurring within and
around estuaries that effect their specific characteristics.
Normally estuaries occupy the areas of the coast least exposed to the marine
action. In this way, wave activity is generally quite reduced, allowing the development
of harbors, recreational facilities, or appropriate aquaculture initiatives. Neverthe-
less, within the estuaries the dynamical processes are rather strong and impose a
remarkable stress over the biota, either permanent or temporary, the morphology
and the civil works.
Some authors have indicated that "estuaries have been uncommon features during
most of earth's history..." (Russell, 1967), simply because "estuarine deposits rarely
can now be delimited unequivocally from other shallow water marine deposits in the
geological record because of their limited areal extent, their ephemeral character and
their lack of distinctive features" (Schubel and Hirschberg, 1978). Nevertheless, as
elbaT 1-1
tnemerusaeM units no eht laropmet-ecaps elacs (after ollireP dna ,ottongidoC )9891
elacsageM elacsorcaM elacsoseM elacsorciM
ecapS mk mk m cm
emiT yrutnec htnom/raey h/syad s/nim
2 G.M.E. PERILLO
Table 2-1
Schematic sequences of sedimentary lithofacies in a transgressive estuarine environment for (a) axial
and vertical trend, and (b) lateral and vertical trend (After Nichols and Biggs, 1985).
(a) Axial and vertical sequence in the estuarine environment
River Seaward Sea
ESTUARINE FLUVIAL ESTUARINE ESTUARINE MARINE
Coarse marine sands massive
with abundant cross-bedding,
tidal current ridges with low an-
gle cross-bedding in fine sands
with silt laminae
Silt and clay with sandy lenses
and laminae, massive silt and
clay deposits
Massive silt and clay with abun-
dant plant and roots, sandy
lenses, and laminations, grading
downward into sand, gravel and
cobble
(b) Lateral and vertical sequence in lower estuary
Shore Mid-channel
SHORELINE DEPOSITS SUBTIDAL FLATS ESTUARINE MARINE
Coarse marine sands massive or
with abundant cross-bedding (as
above)
Laminated and massive muddy
sands and sandy muds
Sand, gravel, and shell with or
without washover complex and
muds with plant frangments and
basal peat
long as a river was present in any paleocoast being affected by tidal action inducing
changes in salinity distribution within its valley, an estuary existed. By the time
Russell (1967) proposed his opinion, there were few unifying models of estuarine
deposition and geologist had difficulties to identify them from other shallow marine
environments. However, Nichols and Biggs (1985) have provided axial and lateral
sequences of estuarine lithofacies in transgressive conditions (Table 1-2). Figure
1-1 is a schematic representation of the evolution process due to high river-load
discharge.
In the present time, estuaries are very common features in most world coasts.
For instance, Emery (1967) estimated that 80-90% of the Atlantic and Gulf coasts
and 10-20% of the Pacific coasts of United States are occupied by estuaries in
the broad sense. The large variety of estuaries that exist depends on the local
climatological, geographic, geological and hydrological characteristics. But also their
GEOMORPHOLOGY DNA SEDIMENTOLOGY OF :SEIRAUTSE NA INTRODUCTION 3
.giF .1-1 Schematic evolutionary sequence of na estuary detaicossa with a large ratio fo river-load input
to sea-level rise. )A Flooding yb the aes of the laivulf ;yellav )B progradation of the coastal plain; )C
gnipoleved of barriers yb littoral transport, dna )D gnipoleved of a river delta.
present position and future evolution largely relies on the variations in sea level,
sediment supply and structural activity.
Therefore, the aim of the present chapter is to consider the basic geomorphologic
and sedimentologic characteristics of estuaries in relation with its global distribution,
factors that influence them and to provide some clues to identify estuaries in the
geological record.
HISTORICAL DNUORGKCAB
Since river mouths have served as natural harbors from the beginning of civiliza-
tions, knowledge of the shallows and channels, tides and currents, and the extent of
salt water penetration has been empirical for the first navigators, city founders and
engineers. Nevertheless, the first morphological charts were introduced by .W Bourne
4 .E.M.G OLLIREP
in 1578. He described the genesis and geomorphology of coasts, including the first
indication of the presence of shoals at river and estuarine mouths.
As geomorphology was initiating in the last decades of the 19th century, much
work was done in coastal environments and, specially, in rivers. They were made
following the Davisian model associated to time evolution stages (youthful-mature-
old) of landscape. However, estuaries were not regarded as a particular separated
entity from the river. Actual interest in estuaries started at the beginning of the
50's, after a series of papers by Pritchard (1952), Stommel (1953) and Stommel and
Farmer (1953) that followed the basic paper by Kuelegan (1949). However, most of
these papers only considered the geomorphology of the estuaries in analyzing the
constrains that the borders introduce in their circulation.
Pritchard (1952) introduced the first physiographic classification, modified by the
same author in 1960 (see discussion by Perillo, this volume). His classification is still
being considered as a good preliminary approach to the understanding of the general
structure of these coastal bodies. Interest in the geomorphology, sedimentology, and
sediment transport of estuaries has increased steadily since them. Classical papers
like those produced by Postma (1961, 1967), Allen et al. (1980) and more recently
Nichols and Biggs (1985) or books by Davis (1985) and Dyer (1986) stand out from a
remarkable list.
Even though the extensive literature and the numerous experiments carried out
in many estuaries in the world, precise knowledge of the actual processes that shape
estuaries, distribute its sediments and control the fate of pollutants and biological
species si still elusive. Integrated approaches has to be devised to understand
individual estuaries or even some particular feature within an estuary.
ECNERRUCCO DNA NOITUBIRTSID FO SEIRAUTSE
As long as freshwater si discharged into the sea in a channeled form, there si
potential for the development of an estuarine environment. Figure 1-2 shows the
distribution of the most important estuaries in the world associated to the tidal range
and climatic zones (many of the estuaries mentioned in the following chapters have
been included in the map). Most estuaries developed in former river valleys are lo-
cated on subtropical and temperate regions and associated with mesotidal conditions.
Those related to previous glacial valleys have formed in polar and subpolar climates.
Pure coastal plain estuaries appear in areas where sediment load provided by the
rivers are relatively small when compared with the dynamic forces that redistribute
the material. Deltas, on the contrary, are found in places where these conditions are
reversed. Although delta tributaries may behave as estuaries themselves.
On the other hand, fjords are concentrated in high latitudes and mostly on rocky
shores, meanwhile the few existing fjards are observed on low-lying coasts of northern
Sweden. Rias are detected in rocky or cliffy shores where alpine glaciation did not
reach into the inundated valley or its modifications cannot be revealed from the river
influence. Structural estuaries cannot be related to any climatic or tidal range criteria,
but to areas presently active like the western boundary of the American continent.