Promotion committee: prof. dr. ir. G.P.M.R. Dewulf University of Twente, chairman and secretary prof. dr. S.J.M.H. Hulscher University of Twente, promotor dr. ir. J.S. Ribberink University of Twente, co-promotor prof. dr. ir. L.C. van Rijn University of Utrecht prof. dr. ir. W.S.J. Uijttewaal University of Delft prof. dr. ir. C.H. Venner University of Twente dr. ir. C.M. Dohmen-Janssen University of Twente dr. ir. D. Hurther University of Grenoble, LEGI, CNRS dr. ir. A. Crosato UNESCO-IHE, Institute for Water Education This study is part of the project named Bed-FormFlood, supported by the Dutch Technology Foundation STW, the applied science division of NWO and the technology program of the Ministry of Economic Affairs, the Netherlands. Cover photo: Sediment transport over a mobile dune (by Suleyman Naqshband) Copyright © 2014 by Suleyman Naqshband, Enschede, The Netherlands All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the written permission of the author. Printed by Gildeprint Drukkerijen, Enschede, The Netherlands ISBN: 978-90-365-3813-8 DOI: 10.3990/1.9789036538138 URL: http://dx.doi.org/10.3990/1.9789036538138 MORPHODYNAMICS OF RIVER DUNES SUSPENDED SEDIMENT TRANSPORT ALONG MOBILE DUNES AND DUNE DEVELOPMENT TOWARDS UPPER STAGE PLANE BED     PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit Twente, op gezag van de rector magnificus, prof. dr. H. Brinksma, volgens besluit van het College voor Promoties in het openbaar te verdedigen op donderdag 18 december 2014 om 14.45 uur door Suleyman Naqshband geboren op 15 september 1985 te Kabul, Afghanistan This thesis is approved by: prof. dr. S.J.M.H. Hulscher promotor dr. ir. J.S. Ribberink co-promotor The inanimate, lifeless cloud that resembles carded cotton has of course no knowledge of us, when it comes to our aid, it is not because it takes pity on us. It cannot appear and disappear without receiving orders. Rather it acts in accordance with the orders of a most Powerful and Compassionate commander. ― Bediüzaman Said Nursî (1877-1960) The Supreme Sign; Observations of a traveller questioning creation CONTENTS Preface ................................................................................................................................ 11 Summary ............................................................................................................................ 13 Samenvatting ..................................................................................................................... 17 1. Introduction ........................................................................................................................ 21 1.1 Rivers, river bedforms and flood management ........................................................... 21 1.2 Controversy in processes controlling dune transition to upper stage plane bed.......... 24 1.3 Research objective ...................................................................................................... 26 1.4 Research questions ...................................................................................................... 26 1.5 Research approach ...................................................................................................... 26 1.6 Thesis outline .............................................................................................................. 28 2. The role of suspended sediment transport and free surface effect in dune transition to upper stage plane bed ................................................................................... 31 Abstract ............................................................................................................................... 31 2.1 Introduction ................................................................................................................. 33 2.2 Method ........................................................................................................................ 35 2.3 Results ......................................................................................................................... 39 2.3.1 Dune Height Evolution ................................................................................... 39 2.3.2 Dune Length Evolution ................................................................................... 41 2.4 Discussion and Conclusions ........................................................................................ 42 3. Contributions of bed load and suspended load transport to dune morphology and dune transition to upper stage plane bed ......................................................................... 45 Abstract ............................................................................................................................... 45 3.1 Introduction ................................................................................................................. 47 3.2 Flume experiments ...................................................................................................... 50 3.2.1 Experimental set-up and instrumentation ....................................................... 50 3.2.2 Experimental procedure .................................................................................. 53 3.2.3 Flow, sediment and bed conditions ................................................................. 56 7 Contents   3.3 Flow structure .............................................................................................................. 58 3.3.1 Mean flow field ............................................................................................... 59 3.3.2 Mean turbulent field ........................................................................................ 63 3.4 Sediment Transport Processes ..................................................................................... 67 3.4.1 Mean sediment concentration ......................................................................... 67 3.4.2 Mean sediment fluxes ..................................................................................... 69 3.4.3 Mean bed and suspended load transport ......................................................... 71 3.5 Discussion and recommendations ............................................................................... 76 3.6 Conclusions ................................................................................................................. 78 4. Contributions of turbulent and advective sediment fluxes to the total sediment fluxes along dunes .............................................................................................................. 81 Abstract ................................................................................................................................ 81 4.1 Introduction ................................................................................................................. 83 4.2 Flume experiments and instrumentation ..................................................................... 85 4.3 Results ......................................................................................................................... 87 4.3.1 Mean streamwise sediment fluxes .................................................................. 87 4.3.2 Mean vertical sediment fluxes ........................................................................ 91 4.4 Discussion and recommendations ............................................................................... 94 4.5 Conclusions ................................................................................................................. 94 5. Modeling river dune development and dune transition to upper stage plane bed ...... 97 Abstract ................................................................................................................................ 97 5.1 Introduction ................................................................................................................. 99 5.2 Dune evolution model ............................................................................................... 102 5.2.1 General description ....................................................................................... 102 5.2.2 Flow module ................................................................................................. 102 5.2.3 Sediment transport module ........................................................................... 104 5.2.4 Bed evolution ................................................................................................ 107 5.3 Flume experiments .................................................................................................... 108 5.3.1 Experimental set-up and procedure ............................................................... 108 5.3.2 Flow, sediment and bed conditions ............................................................... 109 5.4 Model results and comparison with experimental data ............................................. 113 5.4.1 Equilibrium dune development ..................................................................... 113 5.4.2 Dune transition to upper stage plane bed ...................................................... 116 5.5 Discussion and recommendations ............................................................................. 120 5.6 Conclusions ............................................................................................................... 121 6. Discussion .......................................................................................................................... 123 6.1 Dune geometry: low-angle dunes .............................................................................. 124 6.2 Flood management in the Netherlands: Dune – USPB transition? ........................... 125 6.3 Implications for dunes in a broad environment ......................................................... 126 7. Synthesis ............................................................................................................................ 129 7.1 Conclusions ............................................................................................................... 129 7.2 Recommendations ..................................................................................................... 132 References ................................................................................................................................. 135 Publications ............................................................................................................................... 147 About the author ...................................................................................................................... 149 9 10