Preface ix
Part one Thinking globally: the global Earth surface system
1 Fundamentals of the Earth surface system 3
Chapter summary 3
1.1 Introduction 4
1.2 The Earth’s energy balance 5
1.3 The hydrological cycle 7
1.3.1 Role of the hydrological cycle in the global climate system 7
1.3.2 Global heat transfer 11
l.3.3 Ocean–atmosphere interaction: driving mechanisms 11
1.3.4 Summary: a global interactive model 19
1.3.5 Runoff 22
1.4 Role of the biosphere 29
1.4.1 The carbon cycle 31
1.5 Topography and bathymetry 33
1.5.1 The shape of the Earth 33
1.5.2 Isostatic topography 34
1.5.3 The bathymetry of the ocean floor 42
1.5.4 Dynamic topography 43
1.5.5 Continental hypsometries 45
Further reading 48
References 48
2 Environmental change: past, present and future 51
Chapter summary 51
2.1 Introduction: environmental change 52
2.1.1 Significance of the Quaternary 53
2.2 Environmental change associated with glaciation: the record of the Pleistocene 56
2.2.1 The northern hemisphere ice sheets and fringes 57
2.2.2 The marine stable isotope record 60
2.2.3 Information from ice cores 62
2.2.4 Wind-blown dust on land: loess 65
2.2.5 Wind-blown dust in the deep sea 68
2.2.6 Geomorphic change in low latitudes 71
2.3 Post-glacial changes up to the present day 76
2.3.1 Climatic changes in the Holocene 76
2.3.2 Effects of volcanic activity 77
2.4 Causes of past climate change 79
2.4.1 The forcing mechanisms of climate change 79
2.4.2 Sea level change 84
2.5 Human impact 88
2.5.1 Global warming 90
2.5.2 Natural hazards and global climate change 93
Further reading 94
References 94
3 Liberation and flux of sediment 96
Chapter summary 96
3.1 Introduction 97
3.2 Weathering and soils 98
3.2.1 Mechanical weathering 98
3.2.2 Chemical weathering 99
3.2.3 Soils 110
3.3 Sediment routing systems 114
3.3.1 The Indus sediment routing system 116
3.3.2 Modelling the erosional engine of the sediment routing system 117
3.4 Sediment and solute fluxes in drainage basins 128
3.4.1 Bedload 129
3.4.2 Suspended load 129
3.4.3 Solute load 130
3.4.4 Relation between solute and suspended load 131
3.4.5 Sediment rating curves 132
3.5 Sediment yield and landscape models 133
3.5.1 The relation between sediment yield and environmental factors 134
3.5.2 The importance of tectonic activity 135
3.6 Human impact on sediment yield 143
3.6.1 Human impact in the drainage basin 143
3.6.2 Deforestation 144
Further reading 146
References 146
Part two Acting locally: fluid and sediment dynamics
4 Some fluid mechanics 151
Chapter summary 151
4.1 Introduction: the mechanics of natural substances 152
4.1.1 Dimensional analysis 153
4.1.2 The mechanics of clear fluids undergoing shear 155
4.2 Settling of grains in a fluid 156
4.2.1 Fluid resistance or drag 156
4.2.2 Stokes’ law 157
4.2.3 Pressure and shear forces on a particle 159
4.3 Flow down an inclined plane 164
4.4 Turbulent flow 167
4.4.1 The experiments of Reynolds 167
4.4.2 The description of turbulence 167
4.4.3 Structure of turbulent boundary layers 170
4.4.4 Velocity profiles in turbulent flows 174
4.4.5 Flow separation 176
Further reading 178
References 178
5 Sediment transport 179
Chapter summary 179
5.1 Introduction 180
5.1.1 The sediment continuity equation 180
5.2 The threshold of sediment movement under unidirectional flows 181
5.2.1 Forces on a particle resting on a bed 181
5.2.2 Dimensional analysis of the threshold problem 183
5.2.3 The Shields diagram 184
5.3 Modes of sediment transport 186
5.3.1 Bedload 188
5.3.2 Flow resistance and palaeohydrology in bedload rivers 189
5.3.3 Suspended load 193
5.3.4 A diffusion model for suspended sediment concentrations 194
5.4 Bedforms in a cohesionless substrate 198
5.4.1 Froude number 198
5.4.2 Dimensional analysis of bedforms under a shear flow 200
5.4.3 The existence fields of bedforms 201
5.4.4 The flow regime concept 202
5.4.5 Flow over ripples and dunes 203
5.4.6 Stability theory 203
5.4.7 Defect propagation 205
5.4.8 Stratification caused by the migration of bedforms 205
Further reading 208
References 209
6 Hyperconcentrated and mass flows 211
Chapter summary 211
6.1 Introduction 212
6.1.1 Variability of mass flows and hyperconcentrated flows 212
6.2 Soil creep 218
6.3 The initiation of slope failure 219
6.3.1 Friction 219
6.3.2 Strength of natural materials 219
6.3.3 The Navier–Coulomb criterion of failure 220
6.3.4 Sliding on a slope 221
6.3.5 Rotational failures 222
6.3.6 The importance of fluid pressures 222
6.4 The Mechanics of debris flows 223
6.4.1 Bingham plastic model 223
6.4.2 Non-Newtonian fluid model 223
6.4.3 Turbulence in debris flows 224
6.5 Turbidity currents 227
6.5.1 Density currents in nature 227
6.5.2 The mechanics of turbidity currents 228
6.5.3 Deposition from turbidity currents 232
6.6 Pyroclastic density currents 235
Further reading 238
References 239
7 Jets, plumes and mixing at the coast 241
Chapter summary 241
7.1 Introduction to mixing phenomena 242
7.2 Model of a turbulent axisymmetric jet 242
7.3 River outflows 245
7.3.1 Dynamics at river mouths 245
7.3.2 Mississippi outflow case study 252
7.3.3 Modifying marine processes 256
7.3.4 A note on delta classification 257
7.4 Estuaries 258
7.4.1 Estuary types 258
7.4.2 The turbidity maximum and its controls 262
Further reading 265
References 265
8 Tides and waves 267
Chapter summary 267
8.1 Introduction to surface waves 268
8.2 Tidal observations 268
8.3 Ocean tides 270
8.3.1 Tide-generating forces 270
8.3.2 Kelvin waves in the open ocean 274
8.3.3 Tsunamis 275
8.4 Tides in shallow waters 276
8.4.1 Shoaling of ocean tides on the continental shelf 276
8.4.2 Tidal co-oscillation in a partially enclosed sea 277
8.4.3 Tidal currents in shallow waters 282
8.4.4 Tides in estuaries 284
8.4.5 Dissipation of tidal energy 285
8.5 Sediment transport under tidal flows 285
8.5.1 Tidal sandwaves 286
8.6 Wind-generated waves 289
8.6.1 Small-amplitude wave theory 290
8.6.2 Transformations in shallow water 294
8.7 Sediment transport under waves 299
8.7.1 The threshold of sediment movement under waves 299
8.7.2 Wave-generated bedforms 301
Further reading 304
References 304
9 Ocean currents and storms 307
Chapter summary 307
9.1 Introduction 308
9.2 Currents in the ocean 309
9.2.1 An intuitive description of the Coriolis force 309
9.2.2 The wind-driven circulation 310
9.2.3 Currents without friction: geostrophic flows 315
9.2.4 Coastal upwelling and downwelling 318
9.2.5 Effects of sea bed friction on a geostrophic current 319
9.2.6 Interaction between ocean currents and coastal waters 320
9.3 Deep water sediment drifts 321
9.4 Passage of a storm/cyclone 322
9.4.1 The barometric effect 323
9.4.2 Wind set-up 324
9.4.3 Wave set-up 325
9.4.4 The pressure gradient current 326
9.4.5 Sediment transport and bedforms under storms 327
9.5 Storms as hazards 337
Further reading 339
References 339
10 Wind 341
Chapter summary 341
10.1 Introduction 342
10.2 Atmospheric circulation 343
10.2.1 Atmospheric stability 343
10.2.2 The geostrophic wind 344
10.2.3 The planetary wind field 345
10.3 The atmospheric boundary layer 348
10.3.1 The velocity profile in the wind 348
10.3.2 The effect of topography 348
10.4 Sediment transport by the wind 350
10.4.1 Threshold of sediment motion 350
10.4.2 Modes of sediment transport 353
10.5 Aeolian bedforms and deposits 360
10.5.1 Lamination styles 361
10.5.2 Ripples 362
10.5.3 Dunes 365
10.6 Wind as a hazard 367
10.6.1 Strong winds and drought 367
10.6.2 Soil erosion by wind 369
Further reading 371
References 371
11 Glaciers 373
Chapter summary 373
11.1 Introduction: the cryosphere 374
11.2 The dynamics of ice 376
11.2.1 Introduction 376
11.2.2 Non-Newtonian fluid model 377
11.2.3 Ideal plastic model 383
11.2.4 Discharge variations in glaciers 384
11.3 Sediment transport by ice 387
11.3.1 Glacial erosion 387
11.3.2 Glacial deposition 388
11.3.3 Altitudinal zonation of surface process in glaciated landscapes 392
11.3.4 The sediment budget of the Raikot glacier 394
Further reading 396
References 397
Index 398
Philip A. Allen is the author of Earth Surface Processes, published by Wiley.
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