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Bedform Migration in Rivers

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Bedform Migration in Rivers BEDFORM MIGRATION IN RIVERS by Chan-Yi Martin Lin B.Sc., University of Victoria, 2006 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In the Department of Geography Faculty of Environment © Chan-Yi Martin Lin 2011 SIMON FRASER UNIVERSITY Summer 2011 All rights reserved. However, in accordance with the Copyright Act of Canada, this work may be reproduced, without authorization, under the conditions for Fair Dealing. Therefore, limited reproduction of this work for the purposes of private study, research, criticism, review and news reporting is likely to be in accordance with the law, particularly if cited appropriately. APPROVAL Name: Chan-Yi Martin Lin Degree: Master of Science Title of Thesis: Bedform migration in rivers Examining Committee: Chair: Dr. Owen Hertzman Senior Lecturer Department of Geography Simon Fraser University ______________________________________ Dr. Jeremy Venditti Senior Supervisor Assistant Professor Department of Geography Simon Fraser University ______________________________________ Dr. Edward Hickin Committee Member Professor Emeritus Department of Geography Simon Fraser University ______________________________________ Dr. Michael Church External Examiner Professor Emeritus Department of Geography University of British Columbia Date Defended/Approved: June 30th, 2011 ii ABSTRACT Bedform migration rate is important for estimating sediment transport in rivers. Migration rate is difficult to estimate because current theoretical approaches have limited practical use and empirical relations between migration rate and various flow parameters are not well defined. I examine field and flume data that contain information on migration rate and other flow and sediment parameters. I demonstrate an empirical relation between bedform migration rate and transport stage defined by the Shields number. I also report an investigation of the mechanisms of bedform migration in a laboratory experiment in which bed and water-surface topography data were collected under controlled conditions at different transport stages. The experiment shows migration is dominated by translation under bedload-dominated conditions, but bedform shape deformation increases with transport stage, which leads to greater variability in migration rate and bedform geometry. In addition, migration rate is conditioned by suspended- sediment transport mechanisms. Keywords: bedform; river; migration; transport stage; bedload; suspension iii DEDICATION To my Parents To Venerable Ajahn Brahmavamso Mahathera iv ACKNOWLEDGEMENTS I would like to thank my senior supervisor, Dr. Jeremy Venditti, who helped me tremendously. Your time and effort were very much appreciated. I would also like to thank Dr. Edward Hickin for being my on supervisory committee and all his helpful comments and suggestions. Dr. Michael Church offered many insightful critiques and recommendations. I would like to thank Robert Humphries and Natalia Domarad for helping at my experiment and providing intellectual support. I would also like to thank Moslem Kazemi for sharing his knowledge on programming and Dr. Brandon McElroy for providing MATLAB® codes for my data analysis. Lastly, I would like to thank Dr. Tracy Brennand for providing access to the Sedimentary Analysis Laboratory and Dr. Owen Hertzman for many insightful recommendations. I would like to thank all the faculty, staff and fellow students in the Department of Geography. I would especially like to thank, Megan Hendarshot, Elizabeth Baird, Liliana Hill, Marion Walter, Jessica Nelson, Joyce Chen, Chris Au-Yeung, B-Jae Kelly, John Ng, and Justin Song, for their support. v TABLE OF CONTENTS Approval ........................................................................................................................... ii Abstract ........................................................................................................................... iii Dedication ....................................................................................................................... iv Acknowledgements ........................................................................................................ v Table of Contents ........................................................................................................... vi List of Figures .............................................................................................................. viii List of Tables ................................................................................................................. xii List of Notations ........................................................................................................... xiii 1: Chapter 1 ..................................................................................................................... 1 1.1 Introduction ............................................................................................................... 1 1.2 Background ............................................................................................................... 2 1.2.1 Bedforms in river channels ............................................................................ 2 1.2.2 Bedform geometry and relation to transport stage ........................................ 4 1.2.3 Bedform migration and relation to transport stage ...................................... 10 1.2.4 Bedform kinematics ..................................................................................... 14 1.2.5 Linkage between migration rate and transport stage .................................. 17 1.2.6 Perspective ................................................................................................. 20 1.3 Objectives ............................................................................................................... 21 1.4 Thesis format .......................................................................................................... 22 2: Chapter 2 ................................................................................................................... 23 2.1 Introduction ............................................................................................................. 23 2.2 Methods .................................................................................................................. 26 2.3 Results .................................................................................................................... 29 2.3.1 Data assessment ........................................................................................ 29 2.3.2 Bedform geometry and its relation to the Shields number .......................... 30 2.3.3 Regression analysis of all the dune and ripple data .................................... 32 2.3.4 Regression analysis for dune data stratified by H/d .................................... 35 2.3.5 Regression analysis for dune data stratified by d/D .................................... 38 2.3.6 Regression intercepts and slopes ............................................................... 41 2.4 Discussion ............................................................................................................... 43 2.4.1 Bedform migration and its relation to sediment grain size .......................... 43 2.4.2 Application in natural river channels ........................................................... 46 2.5 Perspective ............................................................................................................. 49 vi 3: Chapter 3 ................................................................................................................... 51 3.1 Introduction ............................................................................................................. 51 3.2 Methods .................................................................................................................. 53 3.2.1 Swath Mapping System .............................................................................. 55 3.2.2 Experimental design .................................................................................... 59 3.2.3 Experimental procedure .............................................................................. 64 3.2.4 Data Processing .......................................................................................... 68 3.2.5 Data Analysis .............................................................................................. 70 3.3 Results .................................................................................................................... 84 3.3.1 Flow and sediment transport ....................................................................... 84 3.3.2 Bedform migration ....................................................................................... 88 3.3.3 Bedform characteristics ............................................................................... 98 3.3.4 Bedform translation rate ............................................................................ 109 3.3.5 Bedform translation and deformation ........................................................ 113 3.4 Discussion ............................................................................................................. 117 3.4.1 Effect of transport stage on bedform geometry ......................................... 117 3.4.2 Effect of transport stage on bedform migration ........................................
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