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Investigations into the hydrodynamics of North West Bay

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Matthews, John H and Volframs, Arnold (1977) Investigations into the hydrodynamics of North West Bay. Unspecified thesis, University of Tasmania.

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Abstract

Despite the fact that modern oceanography has been established
since at least the nineteenth century, bays and estuaries appear to have
been singled out for particular study only within the past two decades.
Yet their ecological importance, within the marine complex, is completely
disproportionate to their area. They are generally highly productive
zones and thus a major source of nutrients for coastal communities; they
serve as refuges for many freshwater and marine species; and most
importantly they are frequently important nursery grounds for the
infantile stages of a variety of marine species, many of which spawn and
spend much of their adult life at sea, but return seasonally to the
estuary.
Apart from their importance in the marine complex, bays and
estuaries are undoubtedly amongst man's most valuable natural resources,
being significant to human welfare in a number of diverse, and often
conflicting, roles. Being semi-enclosed they provide natural harbours;
they connect the oceans and the inland rivers so they are natural transportation
centres; they commonly support important fisheries; they
offer scope for a wide range of recreational pursuits; and they are
often convenient repositories for waste disposal. It is in this latter
role that man's impact on estuaries has been the most significant, for
many of the world's major estuaries have become little more than a
septic tank for the urban industrial complex.
The extent of man's pressure on these waters is well illustrated
by the fact that, of the ten largest metropolitan districts in the world,
seven border estuarine areas (New York, Tokyo, London, Shanghai, Buenos
Aires, Osaka and Los Angeles). These cities contain over sixty million
people and foster enormous industrial activity. Ironically, recent
concern with environmental degradation has often only increased the
pressure on waterways. For example, to satisfy clean air regulations
many industries have introduced 'scrubbers', (the Electrolytic .Zinc
Company plant at Risdon, Tasmania, is an example), the effect of which
is not to eliminate pollution but to transfer the pollution load from
the atmosphere to the waterways.
Estuaries are particularly vulnerable to human influences for, being a
confluent for land drainage, they receive the impact of many human
activities throughout an entire watershed. Dams, diversions, irrigations,
agriculture, forestry, changes in run-off due to urbanisation,
and a multitude of other activities all have an ultimate impact on the
complex physical, chemical, and biological interactions that occur
within an estuarine eco-system.
The physical processes that occur within estuaries have a strong
influence on the development and continued viability of their ecosystems.
In general, the most important of these physical factors are,
the circulation, that is the patterns of mass transport and associated
mixing processes such as turbulent diffusion and entrainment, and the
resultant distribution of salinity. To a very large extent they control
the dispersion and the rate of removal of contaminants; patterns of
erosion and sedimentation; exogenous renewal of nutrients, oxygen, and
larvae; and the distribution of estuarine biota.
Thus a detailed knowledge of the hydrodynamic characteristics of
bays and estuaries is not only of extreme importance but also has many
practical applications. To the ecologist and the marine scientist it
is part of the key to understanding the distribution of estuarine flora
and fauna. To the industrialist and the environmental engineer it is
one of the essential elements in evaluating the capacity of any
estuarine or marine environment to receive industrial or domestic wastes.
It should also be an important parameter considered in the planning and
construction of offshore, nearshore, and shoreline structures, and the
design of effluent disposal systems.
Yet the importance of the complex role of estuarine circulation
is often not appreciated. This appears to be particularly true of the
Tasmanian situation where data on the hydrology and hydrodynamics of
estuarine systems is sparse. The present lack of such information
generated interest in carrying out a study into the circulation of a
bay or estuary that is, or is liable to become, an area of environmental
concern.
Due to signs of increasing pressure and development, North West Bay,
an area in close proximity to Hobart, was chosen as the study area.
Brief investigations of its environs were carried out by students of the
Environmental Studies Centre in the third term of 1976. From these pilot
studies it was obvious that little was known about the marine environment
of North West Bay, a situation common to most Tasmanian estuaries. This
stimulated the investigations that are documented in this report.
This report on the study carried out between February and November
1977 has been submitted as part requirements for the degree of Master
of Environmental Studies and represents the culmination of two terms'
work.
As with any research project to be completed within an extremely short
time, the design of the field program for the study area was strongly
influenced by weather conditions, availability of equipment, and
limited manpower.
Hence within these constraints the broad aim of the study were to
provide baseline hydrological and hydrodynamic data and guidelines for
future studies in North West Bay and other estuarine environments in
the region.

Item Type: Thesis (Unspecified)
Keywords: Estuarine ecology, Hydrodynamics
Copyright Holders: The Author
Additional Information:

Thesis (M. Env. St.)--University of Tasmania, 1977. Spiral binding. Bibliography: p. 160

Date Deposited: 19 Dec 2014 02:23
Last Modified: 11 Mar 2016 05:56
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