Gerald Nanson Research

Gerald Nanson Home Page

Introduction
Current Research
Research Students
Progress Report - Large ARC grant

 

1)Western Tasmanian Rivers

2) Extreme Floods in the Illawarra region

3) Kimberley Rivers and late Quaternary palaeoclimate of northwest Australia

4) Lake Eyre and the "drying-out" of Australia

5) Aeolian dunes of central Australia

6) Cooper Creek and Channel Country

7) Dryland rivers of central Australia

8) Tropical Rivers of northern Australia

Quaternary climate and flow regime changes

Anabranching Rivers

Floodplain evolution

INTRODUCTION

Dr Gerald Nanson is a Professor in the School of Geosciences. He has research interests in river channel erosion and floodplain formation of rivers in arid, tropical and temperate-humid regions, anabranching rivers, river rehabilitation and management, deserts and desert dunes and theoretical fluvial geomorphology. He is an active member of the GeoQuEST, with special interests in luminescence dating. His research areas include the Kimberley, Magela Creek in Northern Australia (Arnhem land and the Gulf of Carpentaria), Cooper Creek, Lake Eyre, Central Australian, western Tasmania, and rivers of inland and coastal New South Wales.

Within the School of Geosciences Gerald's undergraduate teaching interests lie in Physical Environments), Fluvial Geomorphology and Field Studies in Physical Geography .

Professor Gerald Nanson has published widely in the fields of fluvial geomorphology, river management, alluvial sedimentation, theoretical geomorphology, flow hydraulics, Quaternary studies and desert geomorphology. He has over 80 refereed scientific publications, mostly in international journals, and presents invited keynote addresses at international scientific meetings Curriculum Vitae. His two primary areas of fluvial research at present are the cause and character of anabranching channels, and investigation of the Principle of Least Action (Maximum Flow Efficiency) as a fundamental of control hydraulic geometry and planform in alluvial rivers (with Dr H.Q. Huang, University of Oxford). The objectives of these two research areas are to explain why, in certain circumstances, stable rivers operate multiple channels, and why alluvial rivers exhibit remarkably consistent and maximally efficient channels over a very wide range of natural environments.

Gerald Nanson has undertaken substantial research into the Quaternary history of the Australian rivers and dunefields. Prior to his work in the Lake Eyre basin (with numerous collaborators) and on the Riverine Plain (with Dr Ken Page of Charles Sturt University), little was known of the huge changes in climate and river regime in the interior of the continent over the past several glacial cycles (about 800,000 years). He has made a particularly contribution to the application of luminescence dating to a wide range of Australian terrestrial environments.

Gerald Nanson is very active in the area of research-student and post-doctoral training, having graduated numerous PhD, MSc and BSc Hons students and supervised several postdoctoral fellows. Since 1995 he has been a distinguished visitor in Geography at the University of Auckland (NZ), the University of Sheffield (UK) and University College, London (UK). By way of competitive research grants, he has been awarded over A$1.5M from the Australian Research Council and the University of Wollongong for Quaternary and fluvial research. He played a pivotal role in fostering geomorphology in Australia, having founded the successful Australian and New Zealand Geomorphology Group, and he was previously Australia's delegate in the International Association of Geomorphologists. He presently serves as a member of the Alligator Rivers Region Technical Committee that advises the Federal Government on the quality of environmental research into the Ranger and Jabiluka uranium mine sites near Jabiru in the Northern Territory.

 

 

CURRENT RESEARCH

Principle of Least Action

In association with his recent postdoctoral fellow, Dr H. Q. Huang (now at the University of Oxford), Professor Nanson is investigating the physical Principle of Least Action that appears to control alluvial channel evolution and equilibrium channel morphology. Theoretical analyses and case studies show that Least Action occurs when fluvial systems operate under conditions determined by the principle of Maximum Flow Efficiency (maximum sediment transport capacity per unit of stream power). In other words, alluvial channels adjust their form to be maximally efficient. In an on going investigation of what controls anabranching rivers in dryland settings, Professor Nanson is completing research into ridge-form anabranching rivers in central Australia with Dr Stephen Tooth (University of Wales, Aberystwyth) looking at the role of vegetation along these stream channels, and the contrasting sedimentological and hydraulic conditions on adjacent single-thread and anabranching systems. Least action has recently been tested in flume study and on an anabranching river in Kakadu National Park (Magela Creek) in collaboration with Dr John Jansen.

Anabranching Rivers

Professor Nanson is a recipient of a 3-year ARC program grant to investigate the processes that form anabranching rivers. This is are the last major river category to be thoroughly described and explained. Less common elsewhere, they are prolific in subhumid, semiarid and tropical regions of Australia where their diversity encourages detailed comparative research. Most previous studies have been sedimentologically based, providing little information suitable for either river management or for palaeo-environmental estimations of flow regime and climate change. This project will expand his recent research into flow efficiency and the principle of least action as the self-adjustment mechanisms controlling alluvial channel form, including the formation of multiple channels. It will also identify best management practices for this characteristically Australian type of river. Postdoctoral research fellow, Dr John Jansen, has undertaken a detailed comparison of the sediment transport efficiency of the anabranching and single-thread reaches of Magela Creek in the Kakadu National Park of the Northern Territory. A flume study has been undertaken to compare anabranching and single-thread rivers under controlled laboratory conditions.

Rapid Induration of Alluvium - Gilbert River

In an investigation of tropical river systems, Professor Nanson, in collaboration with Associate Professor Brian Jones, is investigating the rapid late Quaternary induration of alluvial sediments, and the resultant distortion of channel form and triggering of avulsion events, on the Gilbert River adjacent to the Gulf of Carpentaria. His interests in tropical rivers extend to a recent investigation of the late Quaternary history of fluvial and coastal sequences in southern Vietnam (with Associate Professors Colin Murray-Wallace and Brian Jones).

Quaternary Flow Regime and Climate Change in Australia:- Cooper Creek

Professor Nanson is continuing to pool the alluvial stratigraphic and luminescence information from the Wet-Dry tropics of northern Australia, the Channel Country of the Lake Eyre basin, the coastal rivers of New South Wales and the Riverine Plain of inland souteastern Australia, in order to synthesise an overall picture of flow regime changes across the eastern half of Australia during the past 300,000 years (three glacial cycles). His work shows that Australia had been passing through a sequence of dry and wet episodes associated with the global glacial cycles during the Mid to Late Quaternary. However, superimposed on these oscillations has been a progressive drying trend over this period. The rivers are now only a vestige of their pre-Holocene condition. The Holocene appears to represent an extraordinarily dry interglacial, quite unlike the past two interglacials, and significantly drier than the last interstadial (Stage 3). This work has been conducted in close collaboration with David Price who has undertaken the thermoluminescence dating.

Dryland Rivers

In collaboration with colleagues Dr Stephen Tooth of The University of Wales, Aberystwyth, Dr David Knighton of the University of Sheffield (retired) and Dr Simon Fagan of the University of Aberdeen, Professor Nanson is undertaking research into contemporary dryland river processes. The work is focusing on the muddy rivers and floodplains of the low gradient Cooper Creek in western Queensland and on ridge-form anabranching on the sand load rivers of the moderate-gradient Northern Plains of central Australia NW of Alice Springs. Recent papers have been published on dryland river hydrology, the role of vegetation on dryland rivers, and the formation and maintenance of waterholes.

Mud Aggregates

In collaboration with the late Professor Brian Rust and more recently with Dr Jerry Maroulis, Gerald Nanson has undertaken extensive research into the formation and transport of mud aggregates as sand-sized traction load on the Cooper Creek floodplain. The conditions of transport were replicated in a laboratory flume.

 

RESEARCH STUDENTS (Graduate Students)

Gerald Nanson has an active group of current research students and recent graduates pursuing a variety of research topics around Australia.

Dr Jerry Maroulis (now at University of Southern Queensland) recently completed his PhD thesis (2001) on the stratigraphy and depositional chronology of the Cooper Creek floodplain in southwestern Queensland. His TL dated sections reveal vertically accreting sequences of fluvial and aeolian sediments ranging in age from ~800,000 years at about 30m to modern at the surface. Source bordering dunes and fluvial sediments provide evidence of dramatic Mid to Late Quaternary climate and flow-regime changes in northern and central Australia and yield a sedimentary picture of the evolution of the semi-arid environment of Cooper Creek over this period. Dr Maroulis, Professor Nanson and Professor Gibling (Dalhousie University, Novia Scotia, Canada) are collaborating on a major interpretation of the sedimentology and stratigraphy of Australias low-gradient arid-zone rivers.Particular attention has been paid to the transport and deposition of mud aggregates.

Dr Simon Fagan (now at University of Aberdeen) has recently completed his PhD thesis (2001) on a detailed assessment of the highly variable channel patterns that characterise the Cooper Creek floodplain, focusing particularly on the confluence and bifurcation of the systems multiple channels. He has described an unusual type of levee formation as water is entering rather than leaving large channels. His work follows on from the analyses of the discontinuous distribution of waterholes on the Cooper floodplain and the interpretation of the anabranching and braided nature of rivers in general by Professor Nanson and Dr David Knighton (University of Sheffield) over the past several years.

Dr Maria Coleman has completed her PhD thesis (2002) on the detailed chronology, stratigraphy and history of geomorphological interaction of river and aeolian dune deposits on the Cooper Fan immediately downstream of the Innamincka Dome in South Australia. This region is particularly important for at this point Cooper Creek can switch north to Coongie Lakes (most common at present), south down the Strzelecki Creek to Lake Frome (rarely at present), or due west to Lake Eyre via Lake Hope (every decade or so). The last of these options may have been prevented at various times in the past by the migration of large longitudinal dunes across the path of the Cooper. In the past the southern option has resulted in the filling of Lake Frome and the overflow of Frome northwards into Lake Eyre via the newly discovered (Warrawoocara) overflow channel between Lakes Gregory and Eyre.

Dr Chris Doyle has completed his PhD on the geomorphic Quaternary history, post-European river degradation and proposed rehabilitation of the Nambucca catchment of northern coastal New South Wales. This research has resulted in the completion of a major constancy on the effects of land clearance and gravel extraction along the coastal rivers of this region.

Dr Tim Cohen has completed his PhD (2003) on the geomorphic Quaternary history, floodplain formation, bench formation, and post-European river degradation of the Bellinger River catchment of northern coastal New South Wales.

Dr Ingrid Ward (co-supervised by Assoc. Professor Lesley Head) has completed a PhD on the geomorphic evolution of the archaeologically in the important Keep River region of northern Western Australia in the Kimberley of the monsoon tropics. The work involves establishing the rates of sediment accretion on the extensive sand aprons that flank the sandstone escarpments, outliers and associated Aboriginal rock shelters of this region. She is also examining the rates of upland erosion and sediment supply to these surfaces.

Tim Pietsch is completing a PhD thesis on the Gwyder River on the Western Slopes and Plains of NSW. Part of this project is analysing an extensive system of anabranching rivers in order to determine what causes these very low gradient and fine-grained systems to form multiple channels. The second component is an investigation of the Quaternary history of these rivers, a northern extension of work published recently by Professor Nanson and Dr Ken Page (Charles Sturt University) relating to the Riverine Plain in southern NSW and Victoria.

Graham Grootemaat is undertaking his PhD on the synoptic conditions that have lead to the occurrence of exceptionally large floods in Australia generally, but focusing in particular on central and tropical Australia. The objective is to better understand the climatic conditions that will lead to extreme flood events, and also to understand the conditions that caused major shifts in the hydrology of the continent during the Quaternary.

Kevin Pucillo (co-supervised by Assoc. Professor Brian Jones) is undertaking his PhD on the influence of palaeochannels on groundwater access and movement in the Coleambally Irrigation District. The project involves integrating data from several sources, including a vast amount of borehole data and groundwater measurements from the last 30 years, which will be used to model the effects of different palaeochannel structures on groundwater flow. The work draws on a detailed investigation of the late Quaternary-age Riverine Plain palaeochannel system by Dr Ken Page and Professor Gerald Nanson in the 1990s. A better understanding of groundwater systems in heavily irrigated areas such as Coleambally will provide useful tools for dealing with management issues such as rising water tables and salinity but also help to streamline the efficient use of one of the Riverine Plain’s most valuable resources, water.

Cameron Hollands last year completed a B.Sc Hons thesis on the interaction between aeolian dunes and associated palaeochannels at Camel Flat (southeast of Alice Springs). With Gerald Nanson, he is in the process of publishing two journal articles from this study. With this experience he is undertaking his PhD in the examination of stratigraphy and chronology of the aeolian dunes derived from the Strzelecki Creek, the Mega-Frome beach ridge, and the Warrawoocara Channel. This project will elucidate details of Late Quaternary hydroclimatic changes associated with large-scale drainage disruption of the Lake Eyre Basin of Central Australia.

Earlier reseach students include Dr. Richard (Bert) Roberts (University of Wollongong) of archaeological luminescence dating fame, Dr Ken Page (Charles Sturt University) who has worked extensively on the Riverine Plain of New South Wales, and Dr H.Q Huang (University of Oxford) who is very active in theoretical geomorphology (Principal of least action) and Dr Stephen Tooth (University of Aberystwyth) who is now internationally known for his work on dryland rivers and bedrock channels.

 

 

PROGRESS REPORT: ARC Grant AS39804185.

Chief Investigator: Prof. G.C. Nanson

Anabranching rivers, their causes, characteristics and management (1998-2000)

1) Flume experiments were undertaken in late 1998 and early 1999. They replicate morphological channel changes occurring in straight ridge-form anabranching channels, identified by us in central Australia and the least complex form of anabranching. The first set of runs replicated a river upstream of an anabranching reach and was conducted using the full 450mm wide, sandy bedload flume. The second set was conducted using the same discharge and slope but with channel width reduced by one third to 300mm. The final set was conducted with the same discharge, slope and 300mm total width, but with the flume divided by elongated ridges into three 100mm wide channels. The experiments simulated an enforced width reduction caused in the field by the introduction of cohesive vegetated banks constricting a single channel, or the introduction of cohesive islands producing several constricted channels, with the same water discharge and slope. They produced a ~60% increase in bedload concentration, regardless of whether the channel was divided or not. We now need to undertake further experiments, replicating the introduction of vegetation and associated roughness, to see why it may be advantageous for some rivers to form multiple narrow channels rather than a single narrow channel.

2) The hydraulic models we have developed have been a major outcome of this research project thus far. Constructing a mathematical model we have shown that, where hydraulic gradients cannot be increased, division of a single wide and shallow channel into several narrow and deep channels with a reduced total width will maintain or even enhance sediment flux through a reach where a river may otherwise loose sediment capacity and competence (Nanson and Huang, 1999). This preliminary work on multiple channels lead from necessity to our undertaking detailed mathematical analyses of flow in single channels and a demonstration that rivers operate in such a way as to maximise flow efficiency (MFE) (sediment transported per unit of total stream power). This we have shown to be a product of the general physical principle of least action, and our research offers support for the existing extreme hypotheses of maximum sediment transporting capacity and minimum stream power (Huang and Nanson, 2000). Our most recent research using a wide range of flow resistance and sediment transport functions show that widely observed hydraulic geometry relations (regime channels) reflect conditions of MFE (Huang and Nanson, in review). Because our work on MFE has, for simplicity, been restricted to studying single relatively channels we therefore propose over the three years to examine the role of variations in channel planform, including MFE in multichannelled systems.

3) Flood routing and field morphology studies: Flow during the past two years has been relatively low and the flow measurements were therefore obtained only up to bankfull in 1998. However, from detailed field surveys of channel and waterhole morphology in 1998 and 1999, and access to a large quantity of precise floodplain topographic data from Santos Pty, we have undertaken an analysis of the hydraulic geometry of the anabranching network of minor channels, major channels and waterholes (Knighton and Nanson, in review). Our results show that the channels and waterholes are related to slight variations in floodplain elevation. The present system of channels is very much in equilibrium with the contemporary flow regime (i.e. is not an inherited feature) and velocities in the largest channels rarely exceed 1m/s. Channel cross-sectional area adjusts much more readily than does flow velocity to increases in discharge, and waterholes are flow expansions probably unrelated to pools and riffles but similar to chains-of-ponds (Eyles, 1977). On the Northern Plains (NW of Alice Springs) we have completed a detailed study of ridge-form anabranches that appear to result from within-channel vegetation growth associated with local irrigation from tributaries in this arid region (Tooth and Nanson, 1999). Last year we specifically focused on the role of vegetation in the formation of ridges (Tooth and Nanson, 2000). We have recently submitted our findings on anabranching as an equilibrium channel style (Tooth and Nanson, in review) from which climate change can be evaluated (Nanson and Tooth, 1999). Our most recent work on channel patterns is discussed in Sections 2 ii d and Study Areas of the application, and it is this that will be the focus of the next three years research.

Conclusion:This project has supported three PhD students (Coleman, Fagan and Pietsch), a full time research associate (Huang) and two part time research associates (Tooth and Wende).