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Sediment yields and stream catchment variation in South-Eastern Tasmania

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Olive, L J(Laurence John) (1973) Sediment yields and stream catchment variation in South-Eastern Tasmania. Unspecified thesis, University of Tasmania.

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Abstract

The study is an examination of the sediment loads and erosion
rates of three small catchments in south-eastern Tasmania. Only that
part of the load known as the wash load has been considered. Also,
the suspension and solution load components of the wash load have been
determined. The bed load has not been examined because of the absence
of any accurate method for its determination.
The previous literature on sediment yields is examined showing
the dominance of work carried out in the United States of America in
this field. Only a small number of studies have been carried out in
Australia, with no previous studies in Tasmania. • A review of methods
used in sediment studies revealed a wide range, many of which proved
unsatisfactory for this study. The method used in this study,
involving the use of ashless filters, was the most accurate known to
the author at the time of the study although it is subject to some
limitations.
A description of the environment of the area is given. The
landforms, geology, vegetation and climate of the three catchments
are similar varying only in the proportions of each catchment which
are made up of the various lithological and vegetational units.
The wash load of the streams was sampled over a period of twelve
months while the suspension and solution loads were examined for only -
three months. From the information obtained sediment rating curves
and daily sediment yields were determined. The computed daily
sediment yields revealed the dominance of individual run-off episodes where up to 20 per cent of the annual load was removed in one episode.
These episodes were separated by long periods of basal flow when
sediment transport was minimal. It also illustrated the importance
of the solution load which made up 65 to 85 per cent of the total
wash load. This high figure is due to some degree to the inability
of the laboratory method to separate colloidal material from the
solution load. The solution load was much more constant than total
wash load with individual run-off episodes not being so dominant.
The suspension load however was extremely concentrated in individual
run-off episodes with only negligible transport during basal flows.
Erosion rates were also determined ranging from 140 to 156 tons
per square mile. These fall into a similar range to those found
elsewhere in Australia. A linear relationship was found between
erosion rates and rainfall in Australia. This contrasts with results
obtained in America where erosion rates increased with rainfall to a
maximum at 12 inches per annum and then decreased as rainfall increased.
These differences are due to differences in vegetation with the American
vegetation changing with climate while that in Australia is relatively
constant.
An examination of the influence of various catchments revealed
significant relationships with lithology and vegetation. Erosion rates
were greatest on sandstone and mudstone areas and lower from dolerite
areas. Also, a greater proportion of the sandstone and mudstone was
carried in suspension while the dolerite was transported in solution
or colloidal suspension. Wash load was also greater from forest areas
than from the other vegetational types. This is due to the lack of
ground cover in the forest area.

Item Type: Thesis (Unspecified)
Keywords: Sediments (Geology)
Copyright Holders: The Author
Copyright Information:

Copyright 1973 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).

Additional Information:

Thesis (M. Sc.)--University of Tasmania, 1974?. Bibliography: p. 178-184

Date Deposited: 03 Feb 2015 03:08
Last Modified: 11 Mar 2016 05:56
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