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Developing a Form-Process Framework to Describe the Functioning of Semi-Arid Alluvial Fans in the Baviaanskloof Valley, South Africa

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Developing a Form-Process Framework to Describe the Functioning of Semi-Arid Alluvial Fans in the Baviaanskloof Valley, South Africa DEVELOPING A FORM-PROCESS FRAMEWORK TO DESCRIBE THE FUNCTIONING OF SEMI-ARID ALLUVIAL FANS IN THE BAVIAANSKLOOF VALLEY, SOUTH AFRICA A thesis submitted in the fulfilment of the requirements of the degree of MASTERS OF SCIENCE of RHODES UNIVERSITY By KERRY LEIGH BOBBINS December 2011 i Abstract The Baviaanskloof catchment is a semi - arid catchment located in the Cape Fold Mountains of South Africa. Little is known about the functioning of the complicated Baviaanskloof fluvial system, in particular the role of alluvial fans. This thesis will contribute to field of geomorphology and, more specifically, the field of fan morphometry, by producing a standalone fan framework outlining methods to investigate the influence of fan external and internal control variables. In this thesis, the framework is applied in the Baviaanskloof Valley alongside a case study and used to develop fan restoration guidelines. The framework incorporates external and internal fan control variables at a valley-wide and local fan scale. External control variables include accommodation space, base-level change, and drainage basin inputs. Internal control variables include fan style, morphometry and fan channels. The application of the framework required the creation of a spatial plan of fans and basins in the valley to measure morphometry data. Outcomes of the applied framework include; an understanding of base-level change on fans, relationships between fan basin characteristics and the fan surface and insight into fan channel processes. Results of the applied framework are investigated further using bivariate (correlation matrix) and multivariate (principle component analysis and regression analysis) analysis techniques. Significant relationships identified are: drainage basin area versus fan area, fan area and fan slope and drainage basin ruggedness and basin size. Primary outcomes of this thesis are an alluvial fan form-process framework, restoration guidelines and key considerations of alluvial fan restoration project which were developed using outcomes of the spatial plan, framework and case study thesis components. Contributions of this thesis to broader alluvial fan morphology science includes new insights into general fan literature by compiling a form- process alluvial fan classification framework to identify external and internal fan control variables and identify fan form. Additions have been made to Clarke’s (2010) evolutionary stages to describe stages 4 and 5 of fan evolution that has been adapted to describe fan evolution and differentiate between stages of mature fan evolution. This thesis has also contributed to the study of alluvial fans in South Africa, particularly in the Baviaanskloof Valley. The layout of the procedural guidelines and key considerations for an alluvial fan project provides a guide for rapid fan assessment for maximum cost and time benefits for stakeholders. ii Acknowledgements I am thankful to the National Research Fund (NRF), Department of Environmental Affairs via Working- for-Water in correspondence with the Gamtoos Irrigation Board (GIB) and LivingLands for funding my Masters research over the last two years. I thank my supervisor Professor Kate Rowntree for her interest and guidance and Professor Fred Ellery for his guidance and advice on field trip excursions. I extend my gratitude to Professor Ian Mieklejohn who has offered me guidance and GIS wisdom in times of need. I would like to thank Dieter van den Broek, Marijn Zwinkles, Julia Glenday, Siliva Weel, Odi Selomane, Bart van Eck and the students of the LivingLands team at the PRESENCE learning village for data, assistance, new insights and a good laugh. I would also like to extend my gratitude to Baviaanskloof farmers Piet Kruger and Willie van Rensburg who are always willing to chat and contribute to alluvial restoration projects. Without them, I would not have been able to gain a holistic perspective of fans in the valley and access my study sites. I am grateful to Lindie Smith - Adao and Julia Glenday for Bavaanskloof data used in my thesis and thank Mike Powell for Baviaanskloof literature. I would also like to thank the following people for their assistance with field work and laboratory work: Rebecca Joubert, Pearl Mzobe, Munyuaradzi Manjoro, Jo Millar, Bennie van der Waal and Glyn Armstrong. To all the Masters Anonymous (MA) members: Philippa Irvine, Pearl Mzobe, Breanne Robb and Jill Moeller thank you for your encouragement and support. I wish you all the best for your final Masters submission and your future ‘space and place’ careers. I will not forget our coffees and cocktails together. Furthermore, I would like to thank my family and friends for your support and encouragement. To Patrick Curran, thank you for being the best field assistant, laboratory assistant and proof-reader. I thank your support and encouragement through the difficult times. Unless otherwise stated, this thesis presents the authors own work. iii Table of Contents Abstract ......................................................................................................................................................................... ii Acknowledgements...................................................................................................................................................... iii Table of Contents ......................................................................................................................................................... iv List of Figures ............................................................................................................................................................... xi List of Tables................................................................................................................................................................ xv Appendices ................................................................................................................................................................. xvi Acronyms and Abbreviations .................................................................................................................................... xvi Chapter 1: Introduction............................................................................................................................................. 1 1.1. Introduction to research ............................................................................................................................... 1 1.2. Fluvial system restoration ............................................................................................................................ 3 1.3. Research Aim, research objectives, research design and project outcomes ................................................ 3 1.3.1. Research aim ....................................................................................................................................... 5 1.3.2. Research objectives ............................................................................................................................. 5 1.3.3. Research outcomes ............................................................................................................................. 5 1.3.4. Research design ................................................................................................................................... 5 1.3.4.i. Developing the alluvial fan framework (Part A) .............................................................................. 6 1.3.4.ii. Applying the framework (Part B) .................................................................................................... 6 Chapter 2: Literature Review .................................................................................................................................... 9 2.1. Introduction .................................................................................................................................................. 9 2.2. Alluvial fan theory ........................................................................................................................................ 9 2.2.1. Defining an alluvial fan ........................................................................................................................ 9 2.2.2. Fan Morphometry ............................................................................................................................. 10 2.2.3. Occurrence ........................................................................................................................................ 11 2.2.4. Alluvial fan control variables ............................................................................................................. 12 2.2.5. Fan morphometry.............................................................................................................................. 13 2.2.6. Alluvial fan evolution ......................................................................................................................... 14 iv 2.2.7. The role of alluvial fans in the landscape .......................................................................................... 15 2.2.7.i. Sediment buffering and coupling .................................................................................................. 16 2.2.7.ii. Fans as aquicludes........................................................................................................................
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