Gravel Bed Rivers E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 1693

Veröffentlichungsjahr: 2012

Beschreibung

Gravel-Bed Rivers: Processes, Tools, Environments presents a definitive review of current knowledge of gravel-bed rivers, derived from the 7th International Gravel-bed Rivers Workshop, the 5-yearly meeting of the world's leading authorities in the field. Each chapter in the book has been specifically commissioned to represent areas in which recent progress has been made in the field. The topics covered also represent a coherent progression through the principal areas of the subject (hydraulics; sediment transport; river morphology; tools and methods; applications of science). * Definitive review of the current knowledge of gravel-bed rivers * Coverage of both fundamental and applied topics * Edited by leading academics with contributions from key researchers * Thoroughly edited for quality and consistency to provide coherent and logical progression through the principal areas of the subject.

Leseprobe

Contents

Cover

Title Page

Copyright

List of Contributing Authors

Preface

Secondary Flows in Rivers

Chapter 1: Secondary Flows in Rivers: Theoretical Framework, Recent Advances, and Current Challenges

1.1 Introduction

1.2 Theoretical Framework

1.3 Secondary Currents and Turbulence

1.4 Secondary Currents and Hydraulic Resistance

1.5 Secondary Currents, Sediments and Morphodynamics

1.6 Secondary Currents and Mixing Processes

1.7 Conclusions

1.8 Acknowledgements

1.9 References

1.10 Discussion

Chapter 2: Secondary Flows in Rivers: The Effect of Complex Geometry

2.1 Introduction

2.2 Background

2.3 Channel non-Uniformity and Secondary Flows

2.4 Discussion

2.5 References

Chapter 3: Aspects of Secondary Flow in Open Channels: A Critical Literature Review

3.1 Introduction

3.2 Secondary Flows and Channel Form

3.3 Secondary Flows and Channel Roughness

3.4 Secondary Flows and River Morphodynamics

3.5 Conclusions

3.6 References

Sediment Transport

Chapter 4: Gravel Transport in Granular Perspective

4.1 Introduction

4.2 Granular Flows

4.3 Full Mobility Transport

4.4 Surface Processes

4.5 Bedload Fluctuations, Sheets, and Patches

4.6 Perspectives and Conclusions

4.7 Acknowledgements

4.8 References

4.9 Discussion

4.10 Discussion References

Chapter 5: On Gravel Exchange in Natural Channels

5.1 Introduction

5.2 Geometric Limits to Exchange Sites

5.3 Gravel Exchange

5.4 Exchange Depths

5.5 Exchange and Size Segregation

5.6 Conclusions

5.7 Acknowledgements

5.8 References

5.9 Discussion

5.10 Discussion References

Modelling Morphodynamics

Chapter 6: Morphodynamics of Bars in Gravel-bed Rivers: Bridging Analytical Models and Field Observations

6.1 Introduction

6.2 Analytical Models of Bars in Gravel Bed Rivers: Formulation, Terminology, and Solution Approach

6.3 Morphodynamics of Steady Bars in Single-Thread Channels

6.4 Analytical Bar Models and Multiple-Thread Channel Morphodynamics

6.5 Conclusions and Research Perspectives

6.6 Acknowledgements

6.7 References

6.8 Discussion

6.9 Discussion References

Chapter 7: Field Observations of Gravel-bed River Morphodynamics: Perspectives and Critical Issues for Testing of Models

7.1 Introduction

7.2 Field Studies on Bar Dynamics: New Perspectives from Remote-Sensing Techniques?

7.3 Selection of Test Reaches: Equilibrium and Unstable Condition of River Channels

7.4 Active Channel Width in Braided Rivers

7.5 Final Remarks

7.6 Acknowledgements

7.7 References

Chapter 8: Morphodynamics of Bars in Gravel-bed Rivers: Coupling Hydraulic Geometry and Analytical Models

8.1 Introduction

8.2 Prediction of Channel Patterns

8.3 Summary and Conclusions

8.4 References

Chapter 9: Modelling Sediment Transport and Morphodynamics of Gravel-bed Rivers

9.1 Introduction

9.2 Erosion, Transport, and Deposition of Non-Uniform Sediment

9.3 Analytical Solutions

9.4 Bank Erosion and Bank Accretion

9.5 Vegetation Dynamics and Ecomorphology

9.6 Validation

9.7 Conclusions

9.8 Acknowledgements

9.9 References

9.10 Discussion

Chapter 10: The Potential of using High-resolution Process Models to Inform Parameterizations of Morphodynamic Models

10.1 Introduction

10.2 Process Modelling of Gravel Bed Rivers

10.3 Modelling Flow in a Gravel Bed River using a Computational Fluid Dynamics Approach

10.4 Is discrete particle modelLing an underused method in gravel-bed rivers?

10.5 Sediment transport predictions with high-resolution hydraulics

10.6 How can this information be used to scale up?

10.7 Discussion and Conclusions

10.8 References

Chapter 11: The Importance of Off-channel Sediment Storage in 1-D Morphodynamic Modelling

11.1 Introduction

11.2 Review of 1-D Profile Modelling Approaches

11.3 Inferences Based on Planimetric Centreline Evolution Models

11.4 1-D Profile Modelling with Active Reservoirs for Channel and Lateral Storage

11.5 A Simple 1-D Model with Off-Channel Storage

11.6 Conclusions

11.7 Acknowledgements

11.8 References

11.9 Notation

River Restoration and Regulation

Chapter 12: Stream Restoration in Gravel-bed Rivers

12.1 Introduction

12.2 Restoration Practice and the Research Perspective

12.3 Elements of A Successful Stream Restoration Profession

12.4 Challenges

12.5 Conclusions

12.6 References

12.7 Discussion

Chapter 13: River Restoration: Widening Perspectives

13.1 Introduction

13.2 Matters of Definition

13.3 Towards Intelligent Design: Sorting form from Functionand Alternatives to the Alluvial Paradigm

13.4 Improving Inventory from the Stock of Altered River Systems

13.5 The Societal and Social Dimensions

13.6 Conclusions

13.7 Acknowledgements

13.8 References

13.9 Discussion

Chapter 14: Restoring Geomorphic Resilience in Streams

14.1 Introduction

14.2 Reactions to the Wilcock Review

14.3 Restoration of Stream Geomorphic Resilience

14.4 Summary and Conclusions

14.5 Acknowledgements

14.6 References

Chapter 15: The Geomorphic Response of Gravel-bed Rivers to Dams: Perspectives and Prospects

15.1 Introduction

15.2 A Global Paucity of Data

15.3 Characterizing the Geomorphic Response of Rivers to Impoundment

15.4 Some Perspectives and Conclusions

15.5 Acknowledgements

15.6 References

15.7 Discussion

Chapter 16: Mitigating Downstream Effects of Dams

16.1 Introduction

16.2 Gravel Augmentation Downstream from Dams

16.3 Downstream Propagation and Response Time

16.4 Summary

16.5 References

Ecological Aspects of Gravel-Bed Rivers

Chapter 17: River Geomorphology and Salmonid Habitat: Some Examples Illustrating their Complex Association, from Redd to Riverscape Scales

17.1 Introduction

17.2 Salmonid Spawning Habitat

17.3 A “Riverscape” Perspective into Salmonid Habitat Science

17.4 Acknowledgements

17.5 References

Chapter 18: Incorporating Spatial Context into the Analysis of Salmonid–Habitat Relations

18.1 Introduction

18.2 Uncertainty in Fish–Habitat Relations

18.3 Problems with Density as a Measure of Abundance

18.4 Predicting the Locations of Areas with Locally High Abundance

18.5 Scaling up for Greater Predictive Power

18.6 Acknowledgements

18.7 References

Chapter 19: Animals and the Geomorphology of Gravel-bed Rivers

19.1 Introduction

19.2 It is not only “Habitat” that Matters

19.3 Geomorphological Impacts of Animals in Gravel-Bed Rivers

19.4 Understanding the Mechanisms of Animal Impacts: Laboratory and Field Experiments with Signal Crayfish

19.5 Conclusions

19.6 References

19.7 Discussion

Chapter 20: Geomorphology and Gravel-bed River Ecosystem Services: Workshop Outcomes

20.1 Introduction

20.2 Workshop Structure

20.3 Workshop Outcomes

20.4 Future Research and Challenges

20.5 Acknowledgements

20.6 References

20.7 Appendix A: Program of The Gbr7 Workshop on Gravel-Bed River Ecosystem Services Held 8 September, 2010 In Tadoussac, Québec (Canada)

20.8 Appendix B: Working List of Final Ecosystem Services Associated with Rivers

20.9 Appendix C: Working List of Geomorphological Intermediate Ecosystem Services Associated with Rivers

Tools for Study

Chapter 21: Remote Sensing of the Hydraulic Environment in Gravel-bed Rivers

21.1 Introduction

21.2 The Plan View of the River

21.3 The Vertical Dimension

21.4 Bed Sediment Size

21.5 Other Variables and Platforms

21.6 Future Needs and Directions

21.7 Acknowledgments

21.8 References

21.9 Discussion

21.10 Discussion References

Chapter 22: LiDAR and ADCP Use in Gravel-bed Rivers: Advances Since GBR6

22.1 Introduction

22.2 LIDAR

22.3 Application of ADCP for Combined Depth and Velocity Survey

22.4 Example Studies

22.5 Future Developments Towards GBR8

22.6 References

22.7 Discussion

22.8 Discussion References

Chapter 23: Remotely Sensed Topographic Change in Gravel Riverbeds with Flowing Channels

23.1 Introduction

23.2 The wetted channel problem

23.3 Extracting Meaningful Change in Bed Level and Volume from Remotely Sensed Surveys

23.4 Balancing Spatial Detail Against Vertical Accuracy

23.5 Conclusions

23.6 Acknowledgments

23.7 References

Chapter 24: Modern Digital Instruments and Techniques for Hydrodynamic and Morphologic Characterization of River Channels

24.1 Introduction

24.2 Acoustic River Instrumentation

24.3 Close-Range Remote-Sensing River Instrumentation

24.4 Demonstration of Instrument Capabilities

24.5 Discussion and Conclusions

24.6 Acknowledgements

24.7 References

24.8 Discussion

24.9 Discussion References

Chapter 25: Mapping Water and Sediment Flux Distributions in Gravel-bed Rivers Using ADCPs

25.1 Introduction

25.2 Gravel-Bed Versus Sand-Bed ADCP Measurements

25.3 Gravel-Bed Spatial Distributions

25.4 Discussion and Conclusions

25.5 References

Steep Channels

Chapter 26: Recent Advances in the Dynamics of Steep Channels

26.1 Definition of Steep Channels

26.2 Channel Morphology

26.3 Hydrodynamics and Flow Resistance in Steep Channels

26.4 Sediment Transport

26.5 Conclusions

26.6 Acknowledgements

26.7 References

26.8 Discussion

26.9 Discussion References

Chapter 27: Examining Individual Step Stability within Step-pool Sequences

27.1 Introduction

27.2 Current Research

27.3 New Analyses

27.4 Summary

27.5 Acknowledgements

27.6 References

Chapter 28: Alluvial Steep Channels: Flow Resistance, Bedload Transport Prediction, and Transition to Debris Flows

28.1 Introduction

28.2 Flow Resistance and Bedload Transport

28.3 Transition from Bedload Transport to Debris Floods and Debris Flows

28.4 Conclusions

28.5 Acknowledgements

28.6 References

Semi-Alluvial Channels

Chapter 29: Semi-alluvial Channels and Sediment-Flux-Driven Bedrock Erosion

29.1 Introduction

29.2 Controls on Channel Morphology and Steady State

29.3 Processes of Bedrock Erosion

29.4 Erosion Models

29.5 Bedrock Channels in The Stream Power Model Framework

29.6 The Role of Sediment

29.7 Conclusions and Research Needs

29.8 Acknowledgements

29.9 References

29.10 Discussion

29.11 Discussion References

Chapter 30: Transport Capacity, Bedrock Exposure, and Process Domains

30.1 Introduction

30.2 Transport Capacity in the Fluvial Zone

30.3 Upstream of the Fluvial Zone

30.4 References

Chapter 31: Nomenclature, Complexity, Semi-alluvial Channels and Sediment-flux-driven Bedrock Erosion

31.1 Introduction

31.2 Definition of Channel Types

31.3 Steady-State, Dynamic Equilibrium and the Role of Sediment

31.4 New Concepts

31.5 Acknowledgements

31.6 References

River Channel Change

Chapter 32: Changes in Channel Morphology Over Human Time Scales

32.1 Introduction

32.2 Scales of Channel Change

32.3 Spatial and Temporal Variability of Channel Change

32.4 Predicting Channel Change

32.5 Channel Stability and Hydroclimate

32.6 Conclusion

32.7 Acknowledgements

32.8 References

32.9 Appendix

32.10 References for Appendix

32.11 Discussion

32.12 Discussion References

Chapter 33: Channel Response and Recovery to Changes in Sediment Supply

33.1 Introduction

33.2 Magnitude, Frequency, and Effectiveness of Sediment Transport in Non-Equilibrium Systems

33.3 Case Studies

33.4 Closing Remarks: A Practical Case

33.5 Acknowledgements

33.6 References

Chapter 34: Alluvial Landscape Evolution: What Do We Know About Metamorphosis of Gravel-bed Meandering and Braided Streams?

34.1 Introduction

34.2 Data Sources

34.3 Defining Meandering and Braided Streams

34.4 Hydraulic Geometry and the Respective Influence of Water and Sediment Inputs

34.5 The Role of Soil Properties and Vegetation on Bank Stability

34.6 The Record of Channel Metamorphosis

34.7 Discussion and Concluding Remarks

34.8 Acknowledgements

34.9 References

34.10 Discussion

34.11 Discussion References

Chapter 35: Differences in Sediment Supply to Braided and Single-Thread River Channels: What Do the Data Tell Us?

35.1 Introduction

35.2 Key Variables for Estimating Bedload Transport Capacity

35.3 What do the Data and Observations tell us?

35.4 Conclusions

35.5 Acknowledgements

35.6 References

Chapter 36: Can We Link Cause and Effect in Landscape Evolution?

36.1 Introduction

36.2 Non-Linearity in Numerical Modelling

36.3 Model Investigations

36.4 Discussion

36.5 Conclusion

36.6 References

36.7 Discussion

Ice In Gravel-Bed Rivers

Chapter 37: River-Ice Effects on Gravel-Bed Channels

37.1 Introduction

37.2 Thermal Processes

37.3 Aufeis

37.4 Length, Time, and Dynamic Scales

37.5 Bed Material Transport

37.6 Channel Responses to Ice

37.7 Channel Banks

37.8 Defining Effects of Ice

37.9 Concluding Comments

37.10 References

Chapter 38: Is There a Northern Signature on Fluvial Form?

38.1 Introduction

38.2 Driving and Resisting Forces for Sediment Entrainment in Ice-Affected Rivers

38.3 River Ice and Geomorphologic Work

38.4 Universality of Fluvial Form in Ice-Affected Rivers

38.5 Concluding Remarks

38.6 References

Chapter 39: Long-term and Large-scale River-ice Processes in Cold-region Watersheds

39.1 Introduction

39.2 The Necopastic River Data Set

39.3 Some Perspectives on Long-Term and Large-Scale River-Ice Jam Dynamics

39.4 Conclusions

39.5 References

Index

Colour Plates

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Library of Congress Cataloging-in-Publication Data

Gravel bed rivers: processes, tools, environments / edited by Michael Church, Pascale Biron, André G. Roy; with associate editors Peter Ashmore . . . [et al.].

p. cm.

ISBN 978-0-470-68890-8 (cloth)

1. River channels. I. Church, Michael Anthony, 1942- II. Biron, Pascale. III. Roy, André G. IV. Ashmore, Peter.

TC175.G765 2012

551.48′3–dc23                                                                   2011025981

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

List of Contributing Authors

Note: Bold names indicate the corresponding authors

Dominique Arseneault

Département de biologie, chimie et géographie, Université du Québec à Rimouski, Rimouski, Québec, Canada. [email protected]

Laurie Barrier

Institut du Physique du Globe de Paris, Jussieu, Paris, France. [email protected]

Colden V. Baxter

Idaho State University, Pocatello, Idaho, USA. [email protected]

Yves Bégin

Institut National de la Recherche Scientifique, Centre Eau-Terre-Environnement, St.Foy, Québec, Canada. [email protected]

Normand Bergeron

Institut national de la recherche scientifique, Centre Eau-Terre-Environnement, Québec, Canada [email protected]

Walter Bertoldi

School of Geography, Queen Mary University of London, London, UK and Dipartimento di Ingegneria Civile e Ambientale, University of Trento, Trento Italy. [email protected]

Pascale M. Biron

Department of Geography, Planning and Environment, Concordia University, Montreal, Quebec, Canada

Etienne Boucher

CEREGE, Europole Mediterranéen de l'Arbois, Aix-en-Provence, France. [email protected]

Thomas Buffin-Bélanger

Département de biologie, chimie et géographie, Université du Québec à Rimouski, Rimouski, Québec, Canada. [email protected]

John M. Buffington

USDA Forest Service, Rocky Mountain Research Station, Boise, Idaho, USA. [email protected]

Paul A. Carling

Geography and Environment, University of Southampton, Southampton, UK. [email protected]

Michael Church

Department of Geography, The University of British Columbia, Vancouver, British Columbia, Canada. [email protected]

Nicholas J. Clifford

Department of Geography, King's College, London, UK. [email protected]

Francesco Comiti

Faculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, Italy. [email protected]

Thomas J. Coulthard

Department of Geography, University of Hull, Hull, UK. [email protected]

Joanna Crowe Curran

Department of Civil and Environmental Engineering, University of Virginia, Charlottesville, Virginia, USA. [email protected]

Joseph L. Ebersole

US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, Corvallis, Oregon, USA. [email protected]

Robert Ettema

Civil and Architectural Engineering Department, University of Wyoming, Laramie, Wyoming USA. [email protected]

Joanna Eyquem

Parish Geomorphic Ltd., Mississauga, Ontario, Canada. [email protected]

Philippe Frey

CEMAGREF, Unité de recherche Erosion Torrentielle, Neige et Avalanches, Saint-Martin-d'Hères, France. [email protected]

David Gaeuman

Trinity River Restoration Program, Weaverville California, USA. [email protected]

Gordon E. Grant

USDA Forest Service, Pacific Northwest Research Station, Corvalllis, Oregon, USA. [email protected]

Robert E. Gresswell

US Geological Survey, Northern Rocky Mountain Science Center, Bozeman, Montana, USA. [email protected]

Richard J. Hardy

Department of Geography, Durham University, Durham, UK. [email protected]

Judith K. Haschenburger

Department of Geological Sciences, University of Texas at San Antonio, San Antonio, Texas, USA. [email protected]

Marwan A. Hassan

Department of Geography, The University of British Columbia, Vancouver, British Columbia, Canada. [email protected]

George L. Heritage

JBA Consulting, The Bank Quay House, Sankey St., Warrington, UK. [email protected]

D. Murray Hicks

NIWA, Christchurch, New Zealand. [email protected]

Matthew F. Johnson

Department of Geography, Loughborough University, Loughborough, Leicestershire, UK. [email protected]

Edward W. Kempema

Civil and Architectural Engineering Department, University of Wyoming, Laramie, Wyoming USA. [email protected]

Dongsu Kim

Department of Civil and Environmental Engineering, Dankook University, Kyunggido, Korea. [email protected]

Michel Lapointe

Department of Geography, McGill University, Montreal, Québec, Canada. [email protected]

J. Wesley Lauer

Department of Civil and Environmental Engineering, Seattle University, Seattle, Washington, USA. [email protected]

Thomas E. Lisle

USDA Forest Service, Redwood Sciences Laboratory, Arcata, California, USA. [email protected]

Bruce MacVicar

Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada. [email protected]

Luca Mao

Faculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, Italy. [email protected]

W. Andrew Marcus

Department of Geography, University of Oregon, Eugene, Oregon, USA. [email protected]

James P. McNamara

Department of Geosciences, Boise State University, Boise, Idaho, USA. [email protected]

Venkatesh Merwade

School of Civil Engineering, Purdue University, West Lafayette, Indiana, USA. [email protected]

Lyubov V. Meshkova

Geography and Environment, University of Southampton, Southampton, UK. [email protected]

François Métivier

Institut du Physique du Globe de Paris, Jussieu, Paris, France. [email protected]

David J. Milan

Department of Natural and Social Sciences, University of Gloucestershire, Cheltenham, Gloucestershire, UK. [email protected]

Robert G. Millar

Department of Civil Engineering, The University of British Columbia, Vancouver, British Columbia, Canada. [email protected]

Erik Mosselman

Inland Water Systems Unit, Deltares and Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands. [email protected]

Erich R. Mueller

Geography Department, University of Colorado, Boulder, Colorado, USA. [email protected]

Marian Muste

IIHR-Hydroscience & Engineering and Civil & Environmental Engineering Department, The University of Iowa, Iowa City, Iowa, USA. [email protected]

Vladimir Nikora

School of Engineering, Kings College, Aberdeen, UK. [email protected]

Taha B.M.J. Ouarda

Institut National de la Recherche Scientifique, Centre Eau-Terre-Environnement, Québec, Canada. [email protected]

Athanasios (Thanos) N. Papanicolaou

IIHR-Hydroscience & Engineering and Civil & Environmental Engineering Department, The University of Iowa, Iowa City, Iowa, USA. [email protected]

John Pitlick

Geography Department, University of Colorado, Boulder, Colorado, USA. [email protected]

Ian Reid

Department of Geography, Loughborough University, Loughborough, Leicestershire, UK. [email protected]

Colin D. Rennie

Department of Civil Engineering, University of Ottawa, Ottawa, Ontario, Canada. [email protected]

Stephen P. Rice

Department of Geography, Loughborough University, Loughborough, Leicestershire, UK. [email protected]

Dieter Rickenmann

Swiss Federal Research Institute WSL, Birmensdorf, Switzerland. [email protected]

André G. Roy

Département de géographie, Université de Montréal, Montréal, Québec, Canada. [email protected]

Catalina Segura

Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina, USA. [email protected]

Noah P. Snyder

Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, Massachusetts, USA. [email protected]

Nicola Surian

Dipartimento di Geografia, Università di Padova, Padova, Italy. [email protected]

Christian E. Torgersen

US Geological Survey, Forest and Rangeland Ecosystem Science Center, Cascadia Field Station, University of Washington, School of Forest Resources, Seattle, Washington, USA. [email protected]

Marco Tubino

Dipartimento di Ingegneria Civile e Ambientale, University of Trento, Trento Italy. [email protected]

Jens M. Turowski

Swiss Federal Research Institute WSL, Birmensdorf, Switzerland. [email protected]

Marco J. Van De Wiel

Department of Geography, University of Western Ontario, London, Ontario, Canada. [email protected]

Peter R. Wilcock

Department of Geography & Environmental Engineering, Johns Hopkins University, Baltimore Maryland, USA. [email protected]

André E. Zimmermann

Northwest Hydraulics Consultants, Ltd., North Vancouver, British Columbia, Canada. [email protected]

Guido Zolezzi

Dipartimento di Ingegneria Civile e Ambientale, University of Trento, Trento Italy. [email protected]

Preface

The 7th International Gravel Bed Rivers Workshop was held in Canada at Tadoussac, Québec, between 6 and 10 September, 2010. Tadoussac, located on the north shore of the St Lawrence River at the mouth of the Saguenay Fjord, is the oldest settlement in British North America to have been continually occupied by European settlers and their descendents, dating from the establishment of a fur trading station by French colonists in 1600 (the site of a Basque whaling station, intermittently occupied in the late 16th century, is located immediately to the east of Tadoussac). It is still a relatively quiet village and so well fits the tradition of the Gravel Bed Rivers workshops to seek meeting places that permit concentrated discussion, some relaxation, and good meals.

In further keeping with that tradition, the workshop was designed to present an authoritative review of recent progress in understanding the morphology and processes in gravel bed rivers, a review that you have in your hands. Accordingly, the workshop was constructed around a series of invited keynote presentations that reviewed the principal themes selected for the meeting. The format of the workshop was, however, varied from that of past meetings to the extent that formal discussion papers were invited to accompany each keynote paper, the authors of which were the referees of the keynote paper to which they were invited to respond. Those discussions appear in the book as regular chapters.

The themes of the conference, reflected in the title of the book, were processes, tools, and environments. Processes, to provide for reviews of progress in fundamental understanding of gravel bed rivers; tools, to emphasize the important advances of recent years in observing and measuring instruments and methods – particularly advances in remote-sensing methods; environments, to emphasize the diverse conditions that give rise to rivers flowing over coarse-grained materials.

We have, however, introduced some new themes into this conference, in part in recognition of the meeting in Canada, a cold, northern country with abundant rock and fast-flowing rivers, and in part to address emerging topics of high interest. There was a session on ice in gravel bed rivers. Recognizing the importance of hydroelectric power in Canada, a keynote paper specifically considered dams on gravel bed rivers within the larger context of river channel regulation and restoration. In a session on riverine ecology, rivers as the environment for salmonid fishes – a major Canadian resource – was emphasized. Semi-alluvial channels, ones flowing partly on rock, were for the first time considered in a keynote session. At a more fundamental level, the opening theme session was dedicated to secondary flows, an important mediator of river morphology that has not previously been emphasized in the workshops (nor, indeed, sufficiently considered in the discipline). Numerical modelling of gravel bed river morphodynamics, a rapidly advancing art, was featured in another session. River channel change over extended periods was also given theme attention. Sessions on steep channels and on sediment transport – perhaps the most fundamental theme of all – rounded out the meeting.

Our traditional “practical” exercise was also different at this meeting. Always devoted to field work in the past, we felt a bit overwhelmed at the scale of Canadian rivers as a site for a part-day excursion (the St Lawrence opposite Tadoussac is actually a part of an inland sea that occupies a tectonic basin – not gumboot and measuring tape territory). Therefore, we remained in our comfortable hotel and conducted a workshop facilitated by Normand Bergeron and Joanna Eyquem on ecosystem services provided by gravel bed rivers. Again, a new topic for the workshops, but an important and timely one, reported as a full chapter in this volume.

In addition to the keynote and formal discussion papers presented in this book, the meeting attracted 75 poster presentations, many of them by the graduate student contingent, as usual a highly motivated and enthusiastic group. A selection of those posters has become a formal collection presented in a special edition of Earth Surface Processes and Landforms, edited by Peter Ashmore and Colin Rennie.

The meeting, as usual, featured field trips before and after the meeting. Thomas Buffin-Bélanger and André Roy conducted a three-day excursion before the meeting that commenced at Rimouski, on the south shore of the St Lawrence and spent two days investigating the rivers of the Gaspésie region – steep, gravel bed rivers significantly influenced by seasonal ice and subjected to a recent history of intensive log-drives to sawmills at the river mouths. On Saturday evening we made the 62 km crossing of the Gulf of St Lawrence between Matane, in Gaspésie, and Baie-Comeau on the north shore, where hydropower rivers were investigated on the third day. After the conference, Normand Bergeron and Michel Lapointe led a trip from Tadoussac to Québec City that examined river habitat in gravel bed salmon rivers, intensively investigated in recent years by members of the Centre Interuniversitaire de Recherche sur le Saumon Atlantique (CIRSA).

There are many people to thank for the success of the meeting. First, our sponsors, Hydro-Québec and Parish Geomorphic; GEOIDE, the Canadian Research Network of Excellence in Geomatics; Boréas, groupe de recherche sur les environnements nordiques; la Chaire de recherche du Canada en dynamique fluviale; Concordia University; l'Institut National de la Recherche Scientifique: Eau, Terre et Environnement (INRS-ETE); McGill University; The University of British Columbia; l'Université de Montréal; The University of Ottawa; l'Université du Québec à Rimouski (UQAR); The University of Western Ontario. Thanks to Laurence Therrien and Hélène Lamarre who greatly helped with the organization and management of the conference, Linda Lamarre who gave organizational and financial advice, the staff of the Tadoussac Hotel, especially Véronique Gaudreault, who delivered highly professional support through all stages of preparing and conducting the meeting. Maxime Boivin, Laurence Chaput-Desrosiers, Sylvio Demers, Geneviève Marquis, Taylor Olsen, and Michèle Tremblay prepared and helped to conduct the field trips and managed the poster sessions. Eric Leinberger, cartographer at the University of British Columbia Department of Geography, made heroic efforts to standardize the presentation of the figures in the book. Finally, the staff at John Wiley & Sons, especially Rachael Ballard and Fiona Woods have been wonderfully helpful in bringing to publication this most important aspect of the meeting – the permanent record. Finally, we must thank our four editorial associates, who have done so much to ensure the timely production of the book.

Thanks also to Professor Rob Ferguson, who entertained the meeting as its featured banquet speaker with the unofficial and nearly entirely correct history of GBR.

We trust that this book, like its predecessors, will become part of the authoritative record of advances in knowledge and understanding of gravel bed rivers. And we wish the hosts of the next meeting, GBR8, to be held in Japan, as much success as we have enjoyed.

Mike Church

Secondary Flows in Rivers

Chapter 1

Secondary Flows in Rivers: Theoretical Framework, Recent Advances, and Current Challenges

Vladimir Nikora and André G. Roy

1.1 Introduction

Water currents in rivers have fascinated and inspired researchers (and artists) for centuries, as reflected in numerous observations and paintings from ancient times (e.g., 1963; 1995). Leonardo da Vinci's famous drawings are probably the most impressive and insightful examples of such observations. In his sketches and notes he highlighted a number of features of river flows whose signatures could be clearly observed at the water surface, especially behind obstacles and at stream confluences (Figure 1.1). ‘Spiral’ currents are particularly profound among these features and represent a key facet of nearly all of his water drawings. Using an analogy with curling hair, Leonardo summarized his observations as “Observe the motion of the surface of the water, how it resembles that of hair, which has two motions – one depends on the weight of the hair, the other on the direction of the curls; thus the water forms whirling eddies, one part following the impetus of the chief current, and the other following the incidental motion and return flow” (his written comment in Figure 1.1). It is fascinating how this description, given 500 years ago, is similar to a modern view of the mean flow structure as a superposition of the primary flow and the orthogonal secondary flows. Alternatively, Leonardo's comment may also be interpreted as the Reynolds decomposition of the instantaneous velocity into mean (i.e., time-averaged) and fluctuating turbulent components (2009), although the first interpretation seems better justified.