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Field Investigation on Point Bar Dynamics and Planform Evolution in Meandering Rivers

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Field Investigation on Point Bar Dynamics and Planform Evolution in Meandering Rivers FIELD INVESTIGATION ON POINT BAR DYNAMICS AND PLANFORM EVOLUTION IN MEANDERING RIVERS A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Geography and Anthropology by Taylor Rowley B.S., University of Oklahoma, 2012 M.S., Texas A&M University, 2016 May 2020 Acknowledgements First, I would like to thank my advisor, Kory Konsoer, for being excited about barchan dunes the first time we met. After my initial visit, I knew he would be able to guide me through the daunting PhD process with full support. I thank him for hours of help with fieldwork and troubleshooting, discussing data, seeing through my confusing questions, the trust to let me lead field campaigns and drive the boat with expensive instrumentation attached, and the forgiveness for surveying the wrong point bar and losing a crucial dataset. I thank him for introducing me to the multibeam community, without whom I would not have met the amazing researchers in the Grand Canyon Research and Monitoring Center and Mike Mutschler. I thank him for supporting my decision to work multiple jobs while completing my degree and never questioning that I would get the work done. I thank him for pushing me beyond my limits I didn’t know existed. Finally, I sincerely thank him for putting in the time and effort to get me to this point. I would also like to thank Mick Ursic and Eddy Langendoen for unwavering field help, support in data processing/analysis, and hours of phone calls discussing data. Derek Richards, Andrew Webb, and James Smith for providing field, equipment, and software assistance, including the time when James and I floated down the Pearl River for five hours troubleshooting equipment only to realize the I forgot to click a button. Dr. Samuel Bentley, Dr. Bret Collier, Dr. Juan Lorenzo, Dr. Steve Namikas, and Dr. Jill Trepanier, for serving on my committee, being flexible when scheduling, providing guidance through the PhD process, and to Dr. Collier for being my stand-in-the-corner buddy at TEDx. My coworkers at the U.S. Geological Survey and Uptown Climbing for being understanding of my schedule at times and for providing a life and perspective outside of the PhD. Robb Antrobus, Lee Guilbeau, and the late Karl Domangue, the brainchildren of Uptown Climbing, who saved me and inspire me regularly. The Bicycle Shop for providing me ii with my bike and fantastic company, without which I would not have made it this far. My undergraduate and graduate advisors and colleagues for planting the initial seed that let me know I was more than capable of completing a graduate degree. The Oklahoma Water Resources Board who unknowingly guided me down this path – I am forever grateful. The next thank you deserves a paragraph of its own. I would like to thank Clay Tucker, without whom I would not be writing any of this. No amount of writing can express the gratitude I have for the time he has given me. He was always there in times of venting, crying, discussing, laughing, more crying, presentation making, field help, all of it. Clay, this is as much yours as it is mine and I am forever thankful for you. Lastly, I would like to thank my friends and family, especially my parents who have never once questioned the decisions I have made, but are constantly patient, supportive, and proud of me. This research was funded by the Louisiana State University Board of Regents with a Research Competitiveness Subprogram grant, LEQSF(2016-19)-RD-A-06. Research was also funded by a 2017 West-Russell Research Award from the LSU Department of Geography and Anthropology and a 2018 Graduate Student Research Grant from the Geological Society of America. iii TABLE OF CONTENTS Acknowledgements ......................................................................................................................... ii List of Tables ................................................................................................................................. vi List of Figures ............................................................................................................................... vii Abstract ......................................................................................................................................... xii Chapter 1. Introduction ................................................................................................................... 1 1.1. Motivation ............................................................................................................................ 1 1.2. Research Questions and Objectives ..................................................................................... 5 1.3. Research Organization ......................................................................................................... 6 Chapter 2. Literature Review .......................................................................................................... 8 2.1. Meander Planforms .............................................................................................................. 8 2.2. Flow and Morphology in a Simple Meander ..................................................................... 10 2.3. Flow and Morphology in a Complex Meander .................................................................. 13 2.4. Surficial Point Bar Grain Size Distribution........................................................................ 16 2.5. Internal Point Bar Structure................................................................................................ 19 2.6. Methods to Determine Subsurface Point Bar Structure ..................................................... 20 Chapter 3. The Relationship of Point Bar Morphology to Channel Curvature and Planform Evolution ....................................................................................................................................... 24 3.1. Introduction ........................................................................................................................ 24 3.2. Study Area .......................................................................................................................... 28 3.3. Methods .............................................................................................................................. 31 3.4. Results ................................................................................................................................ 38 3.5. Discussion .......................................................................................................................... 52 3.6. Conclusions ........................................................................................................................ 68 Chapter 4. Three-Dimensional Flow Structure in Two Series of Consecutive Bends .................. 70 4.1. Introduction ........................................................................................................................ 70 4.2. Study Area .......................................................................................................................... 74 4.3. Methods .............................................................................................................................. 77 4.4. Results ................................................................................................................................ 80 4.5. Discussion ........................................................................................................................ 103 4.6. Conclusion ........................................................................................................................ 112 Chapter 5. The Relationship of Channel Planform and Point Bar Architecture on Meandering Rivers .......................................................................................................................................... 114 5.1. Introduction ...................................................................................................................... 114 5.2. Study Area ........................................................................................................................ 118 5.3. Methods ............................................................................................................................ 120 5.4. Results .............................................................................................................................. 124 5.5. Discussion ........................................................................................................................ 133 iv 5.6. Conclusion ........................................................................................................................ 141 Chapter 6. Conclusions ............................................................................................................... 143 6.1. Summary of Research Findings ....................................................................................... 143 6.2. Future Work ..................................................................................................................... 149 Works Cited ................................................................................................................................ 153 Vita .............................................................................................................................................
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