Morphodynamics of river dunes: suspended sediment transport along mobile dunes and dune ...

149 Pages·2014·7.13 MB·English

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
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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

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