Fundamentals of Fluvial Geomorphology

275 Pages·2007·9.5 MB·English

by  Ro Charlton

FUNDAMENTALS OF FLUVIAL
GEOMORPHOLOGY

Fundamentals of Fluvial Geomorphology provides an accessible introduction to the study of river landforms and the
processes that shape them. Rivers are significant geomorphological agents which show an amazing diversity of form
and behaviour, reflecting the wide range of environments in which they are found. Highly dynamic in nature, river
channels adjust and evolve over timescales that range from seconds to tens of thousands of years. This book examines
how river systems operate and respond to change and why this understanding is needed for successful river
management.

The book provides a coherent overview of the main concepts in fluvial geomorphology, together with recent
developments in river channel management, clearly illustrating why an understanding of fluvial geomorphology
is vital in channel preservation, environmentally sensitive design and the restoration of degraded river channels.
Starting with an introduction to the fluvial system, the book moves on to cover:

●
Flow and sediment regimes: flow generation; flow regimes; sediment sources, transfer and yield.

●
Channel process: flow characteristics; processes of erosion and sediment transport; interactions between flow
and the channel boundary; deposition.

●
Channel form and behaviour: controls on channel form; channel adjustments; floodplain development; form
and behaviour of alluvial and bedrock-influenced channels.

●
Response to change: how the system responds to change; reconstructing past changes; impacts of climate
change, human activity, tectonics and base-level change.

●
River management: the fluvial hydrosystem; environmental degradation; environmentally sensitive engineering
techniques; river restoration; the role of the fluvial geomorphologist.

Fundamentals of Fluvial Geomorphology is an indispensable text for undergraduate students. It provides straightfor-
ward explanations for important concepts and mathematical formulae, backed up with conceptual diagrams and
appropriate examples from around the world to show what they actually mean and why they are important.
A colour plate section also shows spectacular examples of fluvial diversity.

Ro Charlton lectures in the Geography Department at the National University of Ireland, Maynooth, where she
teaches undergraduate and postgraduate courses in fluvial geomorphology and hydrology. Her research interests
include meandering river canyons in caves and the impact of climate change on water resources.

FUNDAMENTALS OF FLUVIAL
GEOMORPHOLOGY

Ro Charlton

First published 2008 by Routledge
2 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN

Simultaneously published in the USA and Canada
by Routledge
270 Madison Avenue, New York, NY 10016

Routledge is an imprint of the Taylor & Francis Group, an informa business

©2008 Rosemary Charlton

All rights reserved. No part of this book may be reprinted or reproduced or
utilised in any form or by any electronic, mechanical, or other means, now
known or hereafter invented, including photocopying and recording,
or in any information storage or retrieval system, without permission
in writing from the publishers.

British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library

Library of Congress Cataloging in Publication Data
Charlton, Ro.
Fundamentals of fluvial geomorphology/Ro Charlton.
p. cm.
Includes bibliographical references.
1. Fluvial geomorphology. I. Title.
GB561.C475 2007
551.3′55—dc22
2007014030

ISBN10: 0-415-33453-5 (hbk)
ISBN10: 0-415-33454-3 (pbk)
ISBN10: 0-203-37108-9 (ebk)

ISBN13: 978-0-415-33453-2 (hbk)
ISBN13: 978-0-415-33454-9 (pbk)
ISBN13: 978-0-203-37108-4 (ebk)

This edition published in the Taylor & Francis e-Library, 2007.

“To purchase your own copy of this or any of Taylor & Francis or Routledge’s
collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.”

ISBN 0-203-37108-9 Master e-book ISBN

To my parents

C O N T E N T S

List of figures
ix
List of boxes
xiii
List of plates
xv
List of colour plates
xvii
Aims and scope of the book
xviii
Acknowledgements
xxi

1 INTRODUCTION
1

2 THE FLUVIAL SYSTEM
10

3 THE FLOW REGIME
21

4 SEDIMENT SOURCES
37

5 LARGE-SCALE SEDIMENT TRANSFER
52

6 FLOW IN CHANNELS
69

7 PROCESSES OF EROSION, TRANSPORT AND DEPOSITION
93

8 CHANNEL FORM AND BEHAVIOUR
117

9 SYSTEM RESPONSE TO CHANGE
157

10
MANAGING RIVER CHANNELS
177

Notes
201
Glossary of terms
202
References
211
Index
224

L I S T O F F I G U R E S

1.1
Bedrock channels, alluvial channels and a cross-section of a mixed channel reach
2

1.2
The drainage basin
3

1.3
Elements of three-dimensional channel form
5

2.1
The fluvial system subdivided into three zones: the sediment production zone, sediment
transfer zone and sediment deposition zone
12

2.2
Simplified representation of the fluvial system
14

2.3
Schematic representation of complex response in a drainage system
16

2.4
Idealised sketch showing the components of the fluvial system. (a) Channel network.
(b) River reach. (c) Meander bend. (d) Bedforms. (e) Sedimentary structure.
(f) Sedimentary grain
18

2.5
Types of equilibrium observed over different time scales
19

3.1
Surface and subsurface hydrological pathways
22

3.2
(a) Typical annual hydrograph of a temperate zone river. (b) Characteristics of a storm hydrograph
27

3.3
Flow regimes for selected rivers
29

3.4
Regional growth curves, showing the relation between flood magnitude and frequency
34

4.1
Schematic illustration of different sediment sources
37

4.2
Driving and resisting forces acting on a block of slope material
40

4.3
Examples of mass movement. (a) Translational slide. (b) Rotational slide or slump.
(c) Debris flow. (d) Rockfall
41

4.4
Summary of the principal factors controlling water erosion on hillslopes and sediment
yield to river channels
43

4.5
Horton’s model of overland flow and rill formation
45

5.1
Modes of sediment transport
53

5.2
Sediment yield and specific sediment yield for the Hokitika River, New Zealand, and the
Santa Clara River in California, USA
55

5.3
Sediment stores
55

x
LIST OF FIGURES

5.4 Global patterns of suspended sediment yield
56

5.5 Climatic variation of sediment yield
57

5.6 Variation of sediment yield with basin area for seven topographic categories of river basin
58

5.7 The components of a sediment budget for a reach of channel
62

6.1 Basic channel parameters
70

6.2 The effect of channel shape on hydraulic radius
71

6.3 (a) Example of a vertical velocity profile, showing changes in time-averaged velocity with depth,
(b) Channel cross-sections illustrating the effect of channel shape on the velocity distribution
75

6.4 Illustration of the concept of flow continuity
76

6.5 Flow variations through time and space
77

6.6 Illustration of hydraulic drop and hydraulic jump
81

6.7 Flow separation around obstructions and at a channel bend
83

6.8 (a) Velocity profile and boundary layer for turbulent flow, (b) Fully developed flow profile
85

6.9 (a) Hydraulically smooth surface, (b) Hydraulically rough surface
86

6.10 Hydraulic parameters associated with overbank flow
91

7.1 Bank erosion processes
101

7.2 Driving and resisting forces acting on a grain of sediment resting on the bed of a channel
101

7.3 (a) The Hjulstrøm diagram, showing the mean flow velocity at which particles of a given
size are entrained, transported and deposited, (b) A Shields diagram showing the relationship
between the critical dimensionless bed shear stress and the boundary Reynolds number
102

7.4 Bed sediment characteristics. (a) Friction angle. (b) Sheltering. (c) Imbrication. (d) Armour layer.
104

7.5 Bedform variation in sand-bed channels
107

7.6 Idealised diagram of a cluster bedform
108

7.7 Characteristics of suspended sediment transport by rivers
112

8.1 The driving variables and boundary conditions that control the form of a channel reach
118

8.2 Interrelationships amongst form, flow and sediments in active gravel-bed river
119

8.3 Illustration of the Lane balance between stream power and sediment supply
120

8.4 (a) Schematic representation of the variation in channel properties through a drainage basin,
(b) Long profile of the River Ure, North Yorkshire, UK
127

8.5 Schematic diagram of the time scales of adjustment of various channel form components
with given length dimensions in a hypothetical basin of intermediate size
128

8.6 The development of meanders reduces channel slope
129

8.7 Types of channel bar
130

8.8 (a) Cross-sectional view of channel benches, (b) Concave bank bench, (c) Riffle-pool sequence,
(d) Step-pool sequence and (e) Bedrock bars
131

8.9 Some of the features associated with (a) medium-energy non-cohesive meandering floodplains and
(b) low-energy cohesive floodplains
135

8.10 The continuum of variants of channel planform
137

LIST OF FIGURES
xi

8.11 Sinuosity ratio definition
138

8.12 Aspects of meander geometry. (a) Meander wavelength. (b) Radius of curvature. (c) Typical channel
cross-sections
139

8.13 Transformation of a straight channel with a riffle-pool bed into a meandering channel
141

8.14 (a) Flow in a meander bend, (b) Styles of meander migration and cut-off formation
142

8.15 Mechanisms of braid development, based on flume experiments of Leopold and
Wolman (1957) and Ashmore (1991), and cartoons from Ferguson (1993)
147

9.1 Pulsed (top) and ramped (middle) disturbances
160

9.2 Palaeochannel patterns in the Prosna valley near Wieruszów, Poland
170

9.3 Sequence of development of channels in urban areas
172

9.4 Aggradation and degradation at a dam
173

9.5 (a) Schematic diagram showing the relation of the Indus valley profile and channel pattern
to tectonic elements, (b) Meander belt migration as a result of lateral (cross-valley) tilting
174

10.1 The fluvial hydrosystem
183

10.2 The habitat diversity provided by (a) natural and (b) engineered channels
187

10.3 Environmental management techniques. (a) Distant flood embankments. (b) Multi-stage channel.
(c) Bank protection using woven fencing
191

10.4 In-stream structures. (a) Weirs or low dams. (b) Flow deflectors. (c) Sills. (d) Aquatic ledge
195

L I S T O F B O X E S

1.1
Drainage network patterns
4

3.1
The measurement of streamflow
24

3.2
Calculating flood return periods
31

3.3
The frequency and magnitude of channel forming flows
33

5.1
Estimating the suspended sediment load of a river
54

5.2
Using sediment budgets to assess the impacts of land use change in the Coon Creek drainage basin
63

5.3
Case Study: Impacts of gold mining in the Sacramento Valley, California
66

6.1
The du Boys Equation
70

6.2
Energy relationships and the Bernoulli Equation
72

6.3
Flow resistance formulae
78

6.4
Grain Reynolds number
86

6.5
Shear stress distribution within the velocity profile
87

6.6
The logarithmic ‘law of the wall’ for calculating bed shear stress
89

7.1
Example application of the stream power equations
94

7.2
The Shields parameter
103

7.3
Describing the size distribution of bed sediment
105

7.4
Field techniques for assessing rates of bedload transport
109

7.5
Bedload transport formulae
110

8.1
Hydraulic geometry relationships
125

9.1
Predicting the response to changes in discharge and bedload supply
158

9.2
Terrace formation
164

10.1
Case Study: Experimental flooding in the Grand Canyon, USA
194

10.2
Case Study: The River Skerne restoration project
197