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An Environmental Examination Of Sedimentation In Lindisfarne Bay

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Wood, James Michael (1988) An Environmental Examination Of Sedimentation In Lindisfarne Bay. Coursework Master thesis, University of Tasmania.

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Abstract

Lindisfarne Bay is one of several small estuarine bays on the eastern side of the lower
Derwent Estuary near Hobart in southeastern Tasmania. It once contained sandy beaches and
was originally known as Beauty Bay being used as a place for recreational pursuits by
residents of Hobart early after European settlement.
Concomitant with urbanisation of the catchment, industrial activities, and indiscriminate land
use practices has been the problem of sedimentation. Attempts to redress the situation have
included land reclamation and public pressure to replace sand on the beaches.
This study aims to quantify the extent of sediment deposition in Lindisfarne Bay and to
identify sources of sediment from within the catchment by using the caesium radionuclide
tracing and dating technique, by examining levels of heavy metals in the deposited sediment,
and by relating these to the land use history of the Bay and estuary. Core samples were taken to a depth of up to 1.4 m from eight sites around the intertidal zone
of the head of the bay by using a purpose-built coring device. These cores have been
analysed for caesium-137 (137Cs) activity, heavy metal content (cadmium, copper, lead and
zinc), and grain sizes of sediments. Sediment deposition rates are determined to be between
2.7 and 3.3 cm yr-1 by 137Cs analyses. Heavy metal concentrations indicated sedimentation
rates compatible with 137Cs results and maximum levels at depths of 0.5 to 1.0m. Grainsize
analyses formed an important part of the interpretation of sediment dynamics within the Bay
by showing significantly different proportions of mean grainsize between the eastern side and
the western side of the head of the Bay.
An input of reference value for the average areal activity of 137Cs for the region was
established to be 77 .6 mBq cm-2. The source of sediments has been alluded to by further
areal activities of 137Cs distribution in the catchment Natone Hill emerged as a principal
source of sediments.
Before management options can be considered, it is argued that a sound knowledge of the sedimentation problem should be gained. Such an understanding has been achieved and laid
a foundation for appropriate management practices such as minimising sediment escape from
the catchment by reviewing the burning regime of Natone Hill and Gordons Hill, forbidding
the use of off-road vehicles on Natone Hill, and minimising run-off from road sites as well as
installing silt traps to major storm water outlets.
Phasing out of Ministerial exemptions from the Environment Protection Act 1973 for sewage
treatment plants along the lower Derwent Estuary and the Electrolytic Zinc Company of
Australasia Limited is imperative for improving water quality and heavy metal loading to
sediments within the bay. Once the necessary steps have been taken to prevent further
sedimentation and pollution, a program of dredging and foreshore beautification could be
implemented.

Item Type: Thesis (Coursework Master)
Copyright Holders: The Author
Copyright Information:

Copyright 1988 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Date Deposited: 04 Feb 2015 23:39
Last Modified: 22 Aug 2016 01:25
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