Introduction to
Coastal Processes and
Geomorphology
Robin Davidson-Arnott
Cambridge University Press
Contents
Preface page ix
Acknowledgements xi
Part I Introduction 1
1 Introduction 3
1.1 Humans and the coastal zone 3
1.2 Approaches to the study of coasts 5
1.3 Information sources 6
1.4 Approach and organisation 7
2 Coastal geomorphology 10
2.1 Definition and scope of coastal geomorphology 10
2.2 The coastal zone: definition and nomenclature 11
2.3 Factors influencing coastal morphology and processes 13
References 15
Part II Coastal Processes 17
3 Sea level fluctuations and changes 19
3.1 Synopsis 19
3.2 Mean sea level, the geoid, and changes in mean sea level 19
3.3 Changes in mean sea level 23
3.4 Astronomical tides 29
3.5 Short-term dynamic changes in sea level 38
3.6 Climate change and sea level rise 45
References 48
4 Wind-generated waves 52
4.1 Synopsis 52
4.2 Definition and characteristics of waves 52
4.3 Measurement and description of waves 56
4.4 Wave generation 65
4.5 Wave prediction 70
4.6 Wave climate 74
Further reading 76
References 76
5 Waves wave theory and wave dynamics 78
5.1 Synopsis 78
5.2 Wave theories 78
5.3 Wave shoaling and refraction 85
5.4 Wave breaking 92
5.5 Wave groups and low-frequency energy in the surf
and swash zones 108
Further reading 112
References 112
6 Surf zone circulation 116
6.1 Synopsis 116
6.2 Undertow 116
6.3 Rip cells 121
6.4 Longshore currents 129
6.5 Wind and tidal currents 135
Further reading 135
References 135
7 Coastal sediment transport 139
7.1 Synopsis 139
7.2 Sediment transport mechanisms, boundary layers
and bedforms 139
7.3 On offshore sand transport 148
7.4 Longshore sand transport 155
7.5 Littoral sediment budget and littoral drift cells 166
Further reading 176
References 176
Part III Coastal Systems 181
8 Beach and nearshore systems 183
8.1 Synopsis 183
8.2 Beach and nearshore sediments and morphology 183
8.3 Nearshore morphodynamics 202
8.4 Beach morphodynamics 215
References 222
9 Coastal sand dunes 228
9.1 Synopsis 228
9.2 Morphological components of coastal dunes
and dune fields 229
9.3 Plant communities of coastal dunes 231
9.4 Aeolian processes in coastal dunes 235
9.5 Sand deposition 256
9.6 Beach/dune interaction and foredune evolution 258
9.7 Management of coastal dunes 268
References 273
10 Barrier systems 280
10.1 Synopsis 280
10.2 Barrier types and morphology 280
10.3 Barrier dynamics: overwash and inlets 287
10.4 Barrier spit morphodynamics 307
10.5 Barrier islands 312
10.6 Management of barrier systems 317
References 319
11 Saltmarshes and mangroves 325
11.1 Synopsis 325
11.2 Saltmarsh and mangrove ecosystems 325
11.3 Salt marshes 328
11.4 Mangroves 354
11.5 Conservation and management of saltmarshes and
mangroves 361
Further reading 362
References 362
12 Coral reefs and atolls 369
12.1 Synopsis 369
12.2 Corals and reef formation 370
12.3 Geomorphology and sedimentology of coral reefs 375
12.4 Impacts of disturbance on coral reefs 389
Further reading 393
References 393
13 Cliffed and rocky coasts 396
13.1 Synopsis 396
13.2 Cliffed coast morphology 396
13.3 Cliffed coast erosion system 400
13.4 Cohesive bluff coasts 409
13.5 Rock coasts 424
13.6 Shore platforms 427
13.7 Management of coastal cliff shorelines 430
Further reading 434
References 434
Index 439
Preface
This book is designed primarily as a textbook for an upper-level undergraduate course in coastal processes and geomorphology and it stems from a fourth-year course that I have taught for twenty- five years at the University of Guelph. Its primary objective is to provide students with a description of processes acting to erode, transport and deposit sediments in the coastal zone, and of the factors that act in concert with these to produce the infinite variety of features that characterise marine and freshwater coasts around the world. The intent is to provide sufficient information for the reader to be able to then tackle more detailed material available in primary sources such as refereed journal articles, monographs and the World Wide Web.
The students in the course I teach are primarily in the BSc programme in Physical Geography or Earth Surface Science, with a focus on geomorphology and hydrology, but students from a number of other disciplines, including Engineering, Marine Biology and the BA programme in Geography also take the course. In writing this book I have assumed some background in geomorphology or earth sciences and some level of comfort with mathematical equations and basic physics. However, it should still be readable for those who do not have these. It is my hope that the book will also provide a useful reference source for coastal managers and for other scientists and social scientists interested in the coastal zone.
While I have tried to be broad in my coverage and in the examples used, the book invariably reflects my own experiences and approach. This is biased somewhat towards field studies rather than numerical modelling, and to research carried out in Canada, the USA, the Caribbean and Western Europe, as well as travels to Australia and New Zealand. As much as possible I have drawn on the literature in peer-reviewed journals and some monographs, while acknowledging that there is now a wealth of information available on the web. The expectation is that material presented here will make it easier to find and interpret these sources.
Following the introductory two chapters, the book is divided into two roughly equal parts, the first intended to provide an understanding of coastal processes operating on all oceans and large lakes. The second deals with the geomorphology and morphodynamics of a number of coastal environments including beaches, barrier systems, cliffs, coral coasts and saltmarsh and mangrove coasts. A more comprehensive coverage might also include estuaries and deltas, but to treat them in the same level of detail as the other environments would have made the book too long and I was easily persuaded that these could equally be covered in a book dealing with fluvial geomorphology.
The intense media coverage of natural disasters in the coastal zone such as the December 2004 tsunami in the Pacific and Indian oceans, and Hurricane Katrina in the USA have served to focus attention on vulnerability and adaptation to these and other coastal hazards. This is reinforced by the ongoing debate over humaninduced climate change and particularly the predicted increase in the rate of sea level rise and the threat this may pose to populations living in the coastal zone. At the same time there is growing acknowledgement of the need for some comprehensive system of coastal zone management to facilitate adaptation to natural hazards and to reduce human impact on natural coastal systems. This book does deal explicitly with future sea level scenarios in the chapter on sea level and in Part III there is consideration of the potential impact of increasing rates of sea level rise in each of the coastal environments treated there. There are a multitude of good texts and monographs dealing with coastal management so, rather than treating it cursorily in a separate chapter, I have chosen to give some examples of application to specific problems for each coastal environment. It is hoped that the material presented here can be used to provide coastal managers with background on the physical processes and features of the coastal zone which need to be considered in developing management strategies and plans.
A variety of material is available online to supplement the material presented in the book. This includes colour versions of all photographs and diagrams and a consolidated list of references. Virtual field trips providing examples of the coastal environments described in Part III include supplementary photographs, maps diagrams and short videos. A number of key coastal processes are also illustrated with short videos. Finally, data from field experiments that can be used in laboratory exercises for students are included in separate spreadsheets. It is my intention to try to add to this list over the next two years.
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