DRAINAGE DISORGANISATION IN ARID AUSTRALIA AND ITS MEASUREMENT M.E. Sullivan Thesis submitted for the degree of Master of Science, in the School of Geography, University of New South Wales, May 1976 U;;i\f-fiotT7 li? ;I.S.W. I 03537 -8.mR.77 LIBRARY ABSTRACT The concept of drainage disorganisation under aridity is analysed in this study, and factors leading to a state of disorganisation are considered. The methods previously used to measure the level of disorganisation of drainage systems are assessed, and three measures are proposed for this study. One measure is based on the effectiveness of the catchment in generating drainage channels; the other two are concerned with the stream network, one measuring connectivity, and the other the degree of complete­ ness of the hypothetical network reconstructed using Horton's Laws. In the recognition that these measures are based on different aspects of failure of drainage, and tend to emphasise different factors contributing to the disorganisation, they are applied in turn to three extensive catchments from different parts of the Australian arid zone. Differences between these catchments, and between the three measures are considered. A study in greater detail has been carried out on a small stream system in western New South Wales from which the processes of channel breakdown are inferred. An explanation of the floodout process, and its function in the disorganisation of arid zone drainage has also been carried out. Factors contributing to the disorganisation of drainage have thus been examined, and their relative importance assessed within different systems in the arid zone. *. * ACKNOWLEDGEMENTS I would like to thank many people who have inspired and encouraged me in the preparation of this thesis. In particular I wish to thank my two supervisors, Professor Jack Mabbutt and Dr. Fred Bell, for advice and criticism, and for a great deal of time spent on my behalf. To my family, my thanks for patience and co-operation, and to Kevin Maynard, many thanks for much advice and practical help in the preparation of maps and diagrams. I am also grateful to departments of Australian and State Governments which allowed access to unpublished survey data or records. CONTENTS Page ABSTRACT i ACKNOWLEDGEMENTS ii CHAPTER 1 INTRODUCTION 1 Drainage Disorganisation and its Causes 1 Drainage Disorganisation and Aridity 2 CHAPTER 2 MEASURES OF DRAINAGE DISORGANISATION 4 Drainage Terminal and the Extent of Interior Drainage 4 The Degree of Connectivity 8 PvopoirfibvA EA^ecAwe, Ca.Ac/Uw-i&vat , 10 The Consideration of Frequency of Flows 12 Measures of Drainage Disorganisation Used in This Study 14 CHAPTER 3 DRAINAGE DIVISIONS IN THE AUSTRALIAN ARID ZONE 22 Attributes of the Three Measures 22 Drainage Status in the Australian Arid Zone 24 CHAPTER 4 THE GEORGINA-DIAMANTINA SYSTEM 30 The Proportion of the Catchment Hydrologically Effective 30 The Degree of Channel Connectivity 37 The Comparison of Actual and Potential Channel Lengths 47 A Comparison of the Status of Drainage Disorganisation as Indicated by the Three Measures 50 CHAPTER 5 THE FINKE-MACUMBA SYSTEM 53 The Proportion of the Catchment Hydrologically Effective 53 The Degree of Channel Connectivity 60 The Comparison of Actual and Potential Channel Lengths 72 Comparison of Levels of Disorganisation as Indicated by the Three Measures 74 Page CHAPTER 6 FOWLERS CREEK SYSTEM: A STUDY OF CHANNEL BREAKDOWN 76 Fowlers Creek Catchment 77 Changes in the Channel of Fowlers Creek 78 Implications from Fowlers Creek for Drainage Disorganisation 85 CHAPTER 7 DESERT FLOODOUTS 87 The Occurrence and Form of Desert Floodouts 87 Processes Operating to Form Desert Floodouts 89 Mathematical Models Explaining Floodouts 93 Physiographic Controls of the Location of Floodouts 100 CHAPTER 8 THE RIVER LAKES OF THE WESTERN AUSTRALIAN SHIELD: THE EXAMPLE OF THE LAKE WAY-LAKE COWAN SYSTEM 101 The Present Drainage 101 The Proportion of the Catchment Hydrologically Effective 106 The Degree of Channel Connectivity 109 The Comparison of Actual and Potential Channel Lengths 111 The Comparison of the Three Measures of Drainage Disorganisation 113 CHAPTER 9 EFFECTIVENESS OF THE MEASURES OF DRAINAGE DISORGANISATION 116 The Proportion of the Catchment Hydrologically Effective 118 The Degree of Channel Connectivity 121 The Comparison of Actual and Potential Channel Lengths 124 Application of the Three Measures 127 APPENDIX 1 130 BIBLIOGRAPHY 132 LIST OF TABLES Following Number Title Page 2-1 Estimates of areas of interior drainage 5 2-2 Characteristics related to index of aridity 7 4-1 Subcatchment areas and rainfalls, Georgina- Diamantina system 31 4-2 Landsurface proportions, Georgina-Diamantina system 33 4-3 Relief ratios, Georgina-Diamantina system 34 4-4 Actual and potential channel lengths, Georgina-Diamantina system 48 4- 5 Percentage of channel lengths missing, Georgina-Diamantina system 48 5- 1 Topographic and effective catchment areas, Finke-Macumba system 55 5-2 Landsurface proportions, Finke-Macumba system 57 5-3 Percentage of floodout channels, Finke-Macumba system 62 5-4 Upland catchment areas and tributary drainage, Karinga Creek section of Finke-Macumba system 62 5-5 Lengths of unsupported channel, Finke-Macumba system 63 5-6 Estimated bankfull discharges, Finke River 67 5-7 Width/depth ratios and sediment loads, Finke River 68 5-8 Actual and potential channel lengths, Finke- Macumba system 73 5- 9 Percentage of channel lengths missing, Finke-Macumba system 73 6- 1 Channel dimensions and bankfull discharges, Fowlers Creek 79 6- 2 Channel parameters, Fowlers Creek 79 7- 1 Rates of loss of discharge for ephemeral channels 91 8- 1 Topographic and effective catchment areas, Lake Way-Lake Cowan system 106 Number Title Following Page 8-2 Rainfall data, Lake Way-Lake Cowan system 107 8-3 Landsurface proportions, Lake Way-Lake Cowan system 108 8-4 Actual and potential channel lengths, Lake Way-Lake Cowan system 111 8-5 Percentage of channel lengths missing, Lake Way-Lake Cowan system 112 9-1 Application of the three measures of disorganisation to three sample catchments 116 LIST OF FIGURES Following Number Title Page 2-1 Drainage classification of Australia after de Martonne (1927) 8 2-2 Index of aridity for Australia after de Martonne (1927) 8 2-3 Drainage classification of Australia after Hills (1953) 9 2-4 Drainage classification of Australia after Gentilli (1952) 14 2-5 Stages of breakdown of the channel network 17 2- 6 Difference between actual and theoretical mean segment lengths 19 3- 1 Drainage status in the Australian arid zone after Mabbutt (1972) 24 3-2 Climatic classification of arid and semiarid Australia after Meigs (1953) 24 3- 3 Morphostructural divisions in Australia after Mabbutt (1972) 25 4- 1 Drainage network and topographic catchment, Georgina-Diamantina system 30 4-2 Areas of the three subcatchments, Georgina- Diamantina system, which are effectively drained 30 4-3 Rainfall within Georgina-Diamantina catchment 31 4-4 Landsurfaces and relief in Georgina-Diamantina catchment 33 4-5 Stages of channel breakdown in Georgina- Diamantina system 37 4-6 Drainage terminal of Georgina River 38 4-7 Drainage terminal of Sandover River 39 4-8 Graph showing contributory catchment area to channel length for Sandover, Georgina and Diamantina Rivers 40 4-9 Features of floodplain of Diamantina River 42 4-10 Decrease in flood discharge for Coopers Creek 46 4-11 Graph of actual and theoretical mean segment lengths for Georgina-Diamantina channel systems 48 Following Number Title Page 5-1 Drainage network and topographic catchment for Finke-Macumba system 53 5-2 Postulated reconstruction of former drainage associated with Finke River system 53 5-3 Effectively drained areas of Finke and Macumba subcatchments 56 5-4 Landsurfaces and relief in Finke-Macumba catchment 57 5-5 Stages of channel breakdown in Finke-Macumba system 60 5-6 Rainfall probability graph for Finke River catchment 64 5-7 Sectors of Finke River 66 5-8 Locations of surveyed cross-sections along Finke River 67 5-9 Graph showing change in bankful1 discharge along Finke River 67 5-10 Relationship between width/depth ratio and percentage silt and clay along Finke River 68 5-11 Floodout of Finke River 71 5-12 Graph of actual and theoretical mean segment lengths for Finke-Macumba channel systems 73 6-1 Location of Fowlers Creek and relationship to Lake Bancannia 76 6-2 Fowlers Creek catchment 77 6-3 Plan of alluvial channel of Fowlers Creek showing locations of measured cross-sections and three channel sectors 79 6-4 Cross-profiles of channel of Fowlers Creek 79 8-1 Southern Western Australia showing Yilgarn Plateau and drainage on Plateau 101 8-2 Reconstruction of drainage systems of Western Australia mainly after Beard (1968) 103 8-3 Lake Way-Lake Cowan drainage system 104 8-4 Areas of Lake Way-Lake Cowan system effectively drained 106 Following Number Title Page 8-5 Landsurfaces and relief in Lake Way-Lake Cowan catchment 108 8-6 Stages of channel breakdown in Lake Way- Lake Cowan catchment 109 8-7 Graph of actual and theoretical mean segment lengths for Lake Way-Lake Cowan channel systems 111 9-1 Graph of percentage of channel segment lengths missing from three sample catchments 124 LIST OF PLATES Following Number Title Page 4-1 Vertical air photograph of Diamantina River through Channel Country 42 5-1 Vertical air photographs of Finke River 66 5-2 Changes in channel cross-section down Finke River 70 5-3 Vegetation indicators of channel processes in lower Finke River 71 6-1 Vertical air photographs of Fowlers Creek 79 6-2 Changes in channel of Fowlers Creek 84 6-3 Choked distributary channel 85 8-1 Vertical air photographs of Lake Darlot system 109 1. CHAPTER 1 INTRODUCTION Drainage Disorganisation and its Causes This study is concerned with disorganised drainage within the Australian arid zone.