Geomorphology and Natural Hazards

Tim Davies is Professor in the School of Earth and Environment at University of Canterbury, New Zealand. Educated in Civil Engineering in UK in the 1970s, he taught in Agricultural Engineering and subsequently Natural Resources Engineering at Lincoln University, New Zealand before transferring to University of Canterbury in the present millennium to teach into Engineering Geology and Disaster Risk and Resilience. He has published a total of over 140 papers on a range of pure and applied geomorphology topics including river mechanics and management, debris-flow hazards and management, landslides, earthquakes and fault mechanics, rock mechanics and alluvial fans; natural hazard and disaster risk and resilience. Oliver Korup is Professor in the Institute of Environmental Sciences and Geography and the Institute of Geosciences, University of Potsdam, Germany. Following an academic training in Germany and New Zealand, his research and teaching is now at the interface between geomorphology, natural hazards, and data science. He has worked on catastrophic erosion and disturbances in mountain belts, particularly on landslides, natural dams, river-channel changes, and glacial lake outburst floods. John J. Clague is Emeritus Professor at Simon Fraser University. He was educated at Occidental College, the University of California Berkeley, and the University of British Columbia. He worked as a Research Scientist with the Geological Survey of Canada from 1975 until 1998, and in Department of Earth Sciences at Simon Fraser University from 1998 until 2016. Clague is a Quaternary geologist with research specializations in glacial geology, geomorphology, natural hazards, and climate change, and has authored over 200 papers on these topics. He is a Fellow of the Royal Society of Canada and an Officer of the Order of Canada.

Preface xi

Acknowledgements xv

1 Natural Disasters and Sustainable Development in Dynamic Landscapes 1

1.1 Breaking News 1

1.2 Dealing with Future Disasters: Potentials and Problems 5

1.3 The Sustainable Society 10

1.4 Benefits from Natural Disasters 12

1.5 Summary 16

References 16

2 Defining Natural Hazards, Risks, and Disasters 19

2.1 Hazard Is Tied To Assets 19

2.1.1 Frequency and Magnitude 20

2.1.2 Hazard Cascades 24

2.2 Defining and Measuring Disaster 25

2.3 Trends in Natural Disasters 26

2.4 Hazard is Part of Risk 27

2.4.1 Vulnerability 28

2.4.2 Elements at Risk 32

2.4.3 Risk Aversion 35

2.4.4 Risk is a Multidisciplinary Expectation of Loss 36

2.5 Risk Management and the Risk Cycle 37

2.6 Uncertainties and Reality Check 39

2.7 A Future of More Extreme Events? 41

2.8 Read More About Natural Hazards and Disasters 43

References 46

3 Natural Hazards and Disasters Through the Geomorphic Lens 49

3.1 Drivers of Earth Surface Processes 50

3.1.1 Gravity, Solids, and Fluids 50

3.1.2 Motion Mainly Driven by Gravity 52

3.1.3 Motion Mainly Driven by Water 54

3.1.4 Motion Mainly Driven by Ice 56

3.1.5 Motion Driven Mainly by Air 56

3.2 Natural Hazards and Geomorphic Concepts 57

3.2.1 Landscapes are Open, Nonlinear Systems 57

3.2.2 Landscapes Adjust to Maximize Sediment Transport 59

3.2.3 Tectonically Active Landscapes Approach a Dynamic Equilibrium 62

3.2.4 Landforms Develop Toward Asymptotes 65

3.2.5 Landforms Record Recent Most Effective Events 68

3.2.6 Disturbances Travel Through Landscapes 69

3.2.7 Scaling Relationships Inform Natural Hazards 71

References 73

4 Geomorphology Informs Natural Hazard Assessment 77

4.1 Geomorphology Can Reduce Impacts from Natural Disasters 77

4.2 Aims of Applied Geomorphology 80

4.3 The Geomorphic Footprints of Natural Disasters 81

4.4 Examples of Hazard Cascades 86

4.4.1 Megathrust Earthquakes, Cascadia Subduction Zone 86

4.4.2 Postseismic River Aggradation, Southwest New Zealand 90

4.4.3 Explosive Eruptions and their Geomorphic Aftermath, Southern Volcanic Zone, Chile 93

4.4.4 Hotter Droughts Promote Less Stable Landscapes, Western United States 93

References 94

5 Tools for Predicting Natural Hazards 97

5.1 The Art of Prediction 97

5.2 Types of Models for Prediction 100

5.3 Empirical Models 102

5.3.1 Linking Landforms and Processes 102

5.3.2 Regression Models 107

5.3.3 Classification Models 109

5.4 Probabilistic Models 111

5.4.1 Probability Expresses Uncertainty 111

5.4.2 Probability Is More than Frequency 115

5.4.3 Extreme-value Statistics 119

5.4.4 Stochastic Processes 121

5.4.5 Hazard Cascades, Event Trees, and Network Models 122

5.5 Prediction and Model Selection 124

5.6 Deterministic Models 126

5.6.1 Static Stability Models 126

5.6.2 Dynamic Models 127

References 137

6 Earthquake Hazards 145

6.1 Frequency and Magnitude of Earthquakes 145

6.2 Geomorphic Impacts of Earthquakes 148

6.2.1 The Seismic Hazard Cascade 148

6.2.2 Postseismic and Interseismic Impacts 152

6.3 Geomorphic Tools for Reconstructing Past Earthquakes 154

6.3.1 Offset Landforms 155

6.3.2 Fault Trenching 158

6.3.3 Coseismic Deposits 161

6.3.4 Buildings and Trees 166

References 167

7 Volcanic Hazards 173

7.1 Frequency and Magnitude of Volcanic Eruptions 173

7.2 Geomorphic Impacts of Volcanic Eruptions 177

7.2.1 The Volcanic Hazard Cascade 177

7.2.2 Geomorphic Impacts During Eruption 177

7.2.3 Impacts on the Atmosphere 180

7.2.4 Geomorphic Impacts Following an Eruption 181

7.3 Geomorphic Tools for Reconstructing Past Volcanic Impacts 188

7.3.1 Effusive Eruptions 188

7.3.2 Explosive Eruptions 191

7.4 Climate-Driven Changes in Crustal Loads 195

References 197

8 Landslides and Slope Instability 203

8.1 Frequency and Magnitude of Landslides 203

8.2 Geomorphic Impacts of Landslides 210

8.2.1 Landslides in the Hazard Cascade 210

8.2.2 Landslides on Glaciers 212

8.2.3 Submarine Landslides 213

8.3 Geomorphic Tools for Reconstructing Landslides 213

8.3.1 Landslide Inventories 213

8.3.2 Reconstructing Slope Failures 215

8.4 Other Forms of Slope Instability: Soil Erosion and Land Subsidence 218

8.5 Climate Change and Landslides 220

References 225

9 Tsunami Hazards 233

9.1 Frequency and Magnitude of Tsunamis 233

9.2 Geomorphic Impacts of Tsunamis 236

9.2.1 Tsunamis in the Hazard Cascade 236

9.2.2 The Role of Coastal Geomorphology 237

9.3 Geomorphic Tools for Reconstructing Past Tsunamis 241

9.4 Future Tsunami Hazards 252

References 253

10 Storm Hazards 257

10.1 Frequency and Magnitude of Storms 257

10.1.1 Tropical Storms 257

10.1.2 Extratropical Storms 259

10.2 Geomorphic Impacts of Storms 261

10.2.1 The Coastal Storm-Hazards Cascade 261

10.2.2 The Inland Storm-Hazard Cascade 266

10.3 Geomorphic Tools for Reconstructing Past Storms 269

10.3.1 Coastal Settings 270

10.3.2 Inland Settings 273

10.4 Naturally Oscillating Climate and Increasing Storminess 275

References 280

11 Flood Hazards 285

11.1 Frequency and Magnitude of Floods 286

11.2 Geomorphic Impacts of Floods 289

11.2.1 Floods in the Hazard Cascade 289

11.2.2 Natural Dam-break Floods 291

11.2.3 Channel Avulsion 297

11.3 Geomorphic Tools for Reconstructing Past Floods 298

11.4 Lessons from Prehistoric Megafloods 306

11.5 Measures of Catchment Denudation 308

11.6 The Future of Flood Hazards 311

References 315

12 Drought Hazards 323

12.1 Frequency and Magnitude of Droughts 323

12.1.1 Defining Drought 324

12.1.2 Measuring Drought 325

12.2 Geomorphic Impacts of Droughts 326

12.2.1 Droughts in the Hazard Cascade 326

12.2.2 Soil Erosion, Dust Storms, and Dune Building 327

12.2.3 Surface Runoff and Rivers 332

12.3 Geomorphic Tools for Reconstructing Past Drought Impacts 334

12.4 Towards More Megadroughts? 339

References 342

13 Wildfire Hazards 345

13.1 Frequency and Magnitude of Wildfires 345

13.2 Geomorphic Impacts of Wildfires 348

13.2.1 Wildfires in the Hazard Cascade 348

13.2.2 Direct Fire Impacts 348

13.2.3 Indirect and Postfire Impacts 350

13.3 Geomorphic Tools for Reconstructing Past Wildfires 354

13.4 Towards More Megafires? 359

References 361

14 Snow and Ice Hazards 365

14.1 Frequency and Magnitude of Snow and Ice Hazards 365

14.2 Geomorphic Impact of Snow and Ice Hazards 367

14.2.1 Snow and Ice in the Hazard Cascade 367

14.2.2 Snow and Ice Avalanches 367

14.2.3 Jökulhlaups 374

14.2.4 Degrading Permafrost 375

14.2.5 Other Ice Hazards 379

14.3 Geomorphic Tools for Reconstructing Past Snow and Ice Processes 380

14.4 Atmospheric Warming and Cryospheric Hazards 384

References 389

15 Sea-Level Change and Coastal Hazards 395

15.1 Frequency and Magnitude of Sea-Level Change 399

15.2 Geomorphic Impacts of Sea-Level Change 404

15.2.1 Sea Levels in the Hazard Cascade 404

15.2.2 Sedimentary Coasts 404

15.2.3 Rocky Coasts 407

15.3 Geomorphic Tools for Reconstructing Past Sea Levels 408

15.4 A Future of Rising Sea Levels 411

References 414

16 How Natural are Natural Hazards? 419

16.1 Enter the Anthropocene 419

16.2 Agriculture, Geomorphology, and Natural Hazards 424

16.3 Engineered Rivers 430

16.4 Engineered Coasts 435

16.5 Anthropogenic Sediments 438

16.6 The Urban Turn 443

16.7 Infrastructure’s Impacts on Landscapes 445

16.8 Humans and Atmospheric Warming 446

16.9 How Natural Are Natural Hazards and Disasters? 448

References 450

17 Feedbacks with the Biosphere 457

17.1 The Carbon Footprint of Natural Disasters 457

17.1.1 Erosion and Intermittent Burial 460

17.1.2 Organic Carbon in River Catchments 466

17.1.3 Climatic Disturbances 469

17.2 Protective Functions 473

17.2.1 Forest Ecosystems 473

17.2.2 Coastal Ecosystems 478

References 485

18 The Scope of Geomorphology in Dealing with Natural Risks and Disasters 495

18.1 Motivation 496

18.2 The Geomorphologist’s Role 498

18.3 The Disaster Risk Management Process 499

18.3.1 Identify Stakeholders 500

18.3.2 Know and Share Responsibilities 501

18.3.3 Understand that Risk Changes 503

18.3.4 Analyse Risk 504

18.3.5 Communicate and Deal with Risk Aversion 505

18.3.6 Evaluate Risks 507

18.3.7 Share Decision Making 509

18.4 The Future – Beyond Risk? 511

18.4.1 Limitations of the Risk Approach 511

18.4.2 Local and Regional Disaster Impact Reduction 511

18.4.3 Relocation of Assets 513

18.4.4 A Way Forward? 514

References 516

19 Geomorphology as a Tool for Predicting and Reducing Impacts from Natural Disasters 519

19.1 Natural Disasters Have Immediate and Protracted Geomorphic Consequences 519

19.2 Natural Disasters Motivate Predictive Geomorphology 520

19.3 Natural Disasters Disturb Sediment Fluxes 521

19.4 Geomorphology of Anthropocenic Disasters 521

References 523

Glossary 525

Index 531