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Suspended sediment transport and the implications on river channel breakdown: northern Macquarie Marshes, NSW

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posted on 28.03.2022, 02:43 authored by Nicola Rae Smith
The lower Macquarie River flows northwest from Burrendong Dam to its confluence with the Barwon River and forms part of the Murray – Darling Basin. Large-scale (i.e.climate and topography) controls determine the volume, energy of flow and the suspended sediment transport capacity down catchment. Unlike river systems that increase in size and capacity with distance down catchment towards coastal regions, the Macquarie River flows inland where decreases in capacity and size reflect the semi-arid nature of the climate and the lack of perennial tributaries. This study has identified that the small-scale controls of declining discharge, suspended sediment transport and inchannel vegetation promote channel breakdown in the distal reaches of the fluvial system. The impact of declining discharge and in-channel vegetation blocking on thecontemporary suspended sediment transport regime varies in both space and time in the lateral and longitudinal dimensions. Longitudinal and lateral hydrologic connectivity and suspended sediment transport were assessed using flood recurrence intervals, discharge, and total suspended solids data and channel corridor geomorphic units. Contemporary in-channel and floodplain sedimentation rates, using optically stimulated luminescence and unsupported lead-210, were investigated in the northern Macquarie Marshes. These variables were used as tools to assess the spatiotemporal variability of longitudinal and lateral hydrologic connectivity and suspended sediment transportdown catchment. Surface sediment accretion rates ranged from 2.43 g cm-2 yr-1 upstream of channel breakdown, 0.47 g cm-2 yr-1 within the zone of channel breakdown, and 0.077 g cm-2 yr-1 downstream of channel breakdown. Channel – floodplain hydrologic connectivity increases down catchment. The results show a discontinuity of suspended sediment transport through the northern Macquarie Marshes, promoting a positive feedback cycle between declining discharge and specific stream powers, enhancing in-channel sedimentation and vegetation growth. In-channel vegetation blocking and bed aggradation increases the recurrence of overbank flows and sustains the essential ecosystem services provided by dryland wetland systems.

History

Table of Contents

1. Introduction -- 2. Controls on channel morphology and connected river corridors -- 3.The Macquarie River catchment and site selection -- 4. Surface and sedimentary sample collection and analysis methodologies -- 5. Results 1, geomorphological and hydrological characteristics of the lower Macquarie Marshes system -- 6. Results 2, sedimentary attributes & results -- 7. Discussion -- 8. Synthesis and conclusions.

Notes

"January 2014 Includes bibliographical references A thesis submitted as partial fulfilment of the requirements for the degree of Masters of Philosophy"

Awarding Institution

Macquarie University

Degree Type

Thesis MPhil

Degree

MPhil, Macquarie University, Faculty of Science, Department of Environment and Geography

Department, Centre or School

Department of Environment and Geography

Year of Award

2014

Principal Supervisor

Paul Hesse

Additional Supervisor 1

Kirstie Fryirs

Rights

Copyright Nicola Smith 2014. Copyright disclaimer: http://mq.edu.au/library/copyright

Language

English

Jurisdiction

New South Wales

Extent

1 online resource (213 pages) illustrations, maps

Former Identifiers

mq:52999 http://hdl.handle.net/1959.14/1131907