Geomorphology and Natural Hazards – Understanding Landscape Change for Disaster Mitigation

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 ix Acknowledgements xiii 1 Natural Disasters and Sustainable Development in Dynamic Landscapes 1 1.1 Breaking News 1 1.2 Dealing with Future Disasters: Potentials and Problems 4 1.3 The Sustainable Society 5 1.4 Benefits from Natural Disasters 7 1.5 Summary 10 2 Defining Natural Hazards, Risks, and Disasters 13 2.1 Hazard Is Tied To Assets 13 2.1.1 Frequency and magnitude 14 2.1.2 Hazard cascades 16 2.2 Defining and Measuring Disaster 17 2.3 Trends in Natural Disasters 18 2.4 Hazard is Part of Risk 19 2.4.1 Vulnerability 19 2.4.2 Elements at risk 21 2.4.3 Risk aversion 23 2.4.4 Risk is a multidisciplinary expectation of loss 23 2.5 Risk Management and the Risk Cycle 24 2.6 Uncertainties and Reality Check 25 2.7 A Future of More Extreme Events? 26 2.8 Read More About Natural Hazards and Disasters 28 3 Natural Hazards and Disasters through The Geomorphic Lens 33 3.1 Drivers of Earth Surface Processes 34 3.1.1 Gravity, solids, and fluids 34 3.1.2 Motion mainly driven by gravity 36 3.1.3 Motion mainly driven by water 37 3.1.4 Motion mainly driven by ice 39 3.1.5 Motion driven mainly by air 40 3.2 Natural Hazards and Geomorphic Concepts 40 3.2.1 Landscapes are open, nonlinear systems 40 3.2.2 Landscapes adjust to maximise sediment transport 41 3.2.3 Tectonically active landscapes approach a dynamic equilibrium 43 3.2.4 Landforms develop toward asymptotes 44 3.2.5 Landforms record recent most effective events 46 3.2.6 Disturbances travel through landscapes 46 3.2.7 Scaling relationships inform natural hazards 48 4 Geomorphology Informs Natural Hazard Assessment 51 4.1 Geomorphology Can Reduce Impacts from Natural Disasters 51 4.2 Aims of Applied Geomorphology 53 4.3 The Geomorphic Footprints of Natural Disasters 54 4.4 Examples of Hazard Cascades 56 4.4.1 Megathrust earthquakes, Cascadia subduction zone 56 4.4.2 Postseismic river aggradation, southwest New Zealand 58 4.4.3 Explosive eruptions and their geomorphic aftermath, Southern Volcanic Zone, Chile 59 4.4.4 Hotter droughts promote less stable landscapes, western United States 59 5 Tools for Predicting Natural Hazards 63 5.1 The Art of Prediction 63 5.2 Types of Models for Prediction 66 5.3 Empirical Models 67 5.3.1 Linking landforms and processes 68 5.3.2 Regression models 70 5.3.3 Classification models 72 5.4 Probabilistic Models 73 5.4.1 Probability expresses uncertainty 74 5.4.2 Probability is more than frequency 77 5.4.3 Extreme-value statistics 80 5.4.4 Stochastic processes 81 5.4.5 Hazard cascades, event trees, and network models 83 5.5 Prediction and Model Selection 84 5.6 Deterministic Models 85 5.6.1 Static models 85 5.6.2 Dynamic models 86 6 Earthquake Hazards 95 6.1 Frequency and Magnitude of Earthquakes 95 6.2 Geomorphic Impacts of Earthquakes 97 6.2.1 The seismic hazard cascade 97 6.2.2 Post-seismic and inter-seismic impacts 99 6.3 Geomorphic Tools for Reconstructing Past Earthquakes 100 6.3.1 Offset landforms 101 6.3.2 Fault trenching 102 6.3.3 Coseismic deposits 104 6.3.4 Buildings and trees 107 7 Volcanic Hazards 111 7.1 Frequency and Magnitude of Volcanic Eruptions 111 7.2 Geomorphic Impacts of Volcanic Eruptions 113 7.2.1 The volcanic hazard cascade 113 7.2.2 Geomorphic impacts during eruption 114 7.2.3 Impacts on the atmosphere 115 7.2.4 Geomorphic impacts following an eruption 116 7.3 Geomorphic Tools for Reconstructing Past Volcanic Impacts 118 7.3.1 Effusive eruptions 118 7.3.2 Explosive eruptions 120 7.4 Climate-Driven Changes in Crustal Loads 124 8 Landslides and Slope Instability 131 8.1 Frequency and Magnitude of Landslides 131 8.2 Geomorphic Impacts of Landslides 134 8.2.1 Landslides in the hazard cascade 134 8.2.2 Landslides on glaciers 136 8.2.3 Submarine landslides 137 8.3 Geomorphic Tools for Reconstructing Landslides 137 8.3.1 Landslide inventories 137 8.3.2 Reconstructing slope failures 138 8.4 Other Forms of Slope Instability: Soil Erosion and Land Subsidence 141 8.5 Climate Change and Landslides 143 9 Tsunami Hazards 151 9.1 Frequency and Magnitude of Tsunamis 151 9.2 Geomorphic Impacts of Tsunamis 153 9.2.1 Tsunamis in the hazard cascade 153 9.2.2 The role of coastal geomorphology 154 9.3 Geomorphic Tools for Reconstructing Past Tsunamis 155 9.4 Future Tsunami Hazards 162 10 Storm Hazards 165 10.1 Frequency and Magnitude of Storms 165 10.1.1 Tropical storms 165 10.1.2 Extratropical storms 166 10.2 Geomorphic Impacts of Storms 167 10.2.1 The coastal storm-hazards cascade 167 10.2.2 The inland storm-hazard cascade 171 10.3 Geomorphic Tools for Reconstructing Past Storms 172 10.3.1 Coastal settings 173 10.3.2 Inland settings 174 10.4 Naturally Oscillating Climate and Increasing Storminess 175 11 Flood Hazards 181 11.1 Frequency and Magnitude of Floods 182 11.2 Geomorphic Impacts of Floods 183 11.2.1 Floods in the hazard cascade 183 11.2.2 Natural dam-break floods 185 11.2.3 Channel avulsion 189 11.3 Geomorphic Tools for Reconstructing Past Floods 190 11.4 Lessons from Prehistoric Megafloods 194 11.5 Measures of Catchment Denudation 196 11.6 The Future of Flood Hazards 198 12 Drought Hazards 205 12.1 Frequency and Magnitude of Droughts 205 12.1.1 Defining drought 206 12.1.2 Measuring drought 207 12.2 Geomorphic Impacts of Droughts 208 12.2.1 Droughts in the hazard cascade 208 12.2.2 Soil erosion, dust storms, and dune building 208 12.2.3 Surface runoff and rivers 210 12.3 Geomorphic Tools for Reconstructing Past Drought Impacts 211 12.4 Towards More Megadroughts? 215 13 Wildfires 219 13.1 Frequency and Magnitude of Wildfires 219 13.2 Geomorphic Impacts of Wildfires 221 13.2.1 Wildfires in the hazard cascade 221 13.2.2 Direct fire impacts 221 13.2.3 Indirect and post-fire impacts 222 13.3 Geomorphic Tools for Reconstructing Past Wildfires 225 13.4 Towards More Megafires? 227 14 Snow and Ice Hazards 231 14.1 Frequency and Magnitude of Snow and Ice Hazards 231 14.2 Geomorphic Impact of Snow and Ice Hazards 232 14.2.1 Snow and ice in the hazard cascade 232 14.2.2 Snow and ice avalanches 233 14.2.3 Jokulhlaups 236 14.2.4 Degrading permafrost 237 14.2.5 Other ice hazards 239 14.3 Geomorphic Tools for Reconstructing Past Snow and Ice Processes 240 14.4 Atmospheric Warming and Cryospheric Hazards 241 15 Sea-Level Change and Coastal Hazards 247 15.1 Frequency and Magnitude of Sea-Level Change 248 15.2 Geomorphic Impacts of Sea-Level Change 250 15.2.1 Sea levels in the hazard cascade 250 15.2.2 Sedimentary coasts 251 15.2.3 Rocky coasts 253 15.3 Geomorphic Tools for Reconstructing Past Sea Levels 254 15.4 A Future of Rising Sea Levels 257 16 How Natural are Natural Hazards? 263 16.1 Enter the Anthropocene 263 16.2 Agriculture, Geomorphology, and Natural Hazards 266 16.3 Engineered Rivers 270 16.4 Engineered Coasts 272 16.5 Anthropogenic Sediments 274 16.6 The Urban Turn 277 16.7 Infrastructure’s Impacts on Landscapes 278 16.8 Humans and Atmospheric Warming 279 16.9 How Natural Are Natural Hazards and Disasters? 281 17 Feedbacks with the Biosphere 287 17.1 The Carbon Footprint of Natural Disasters 287 17.1.1 Erosion and intermittent burial 289 17.1.2 Organic carbon in river catchments 291 17.1.3 Climatic disturbances 293 17.2 Protective Functions 296 17.2.1 Forest ecosystems 296 17.2.2 Coastal ecosystems 299 18 The Scope of Geomorphology in Dealing with Natural Risks and Disasters 309 18.1 Motivation 310 18.2 The Geomorphologist’s Role 312 18.3 The Disaster Risk Management Process 313 18.3.1 Identify stakeholders 313 18.3.2 Know and share responsibilities 314 18.3.3 Understand that risk changes 315 18.3.4 Analyse risk 316 18.3.5 Communicate and deal with risk aversion 317 18.3.6 Evaluate risks 319 18.3.7 Share decision making 321 18.4 The Future–Beyond Risk? 322 18.4.1 Limitations of the risk approach 323 18.4.2 Local and regional disaster impact reduction 323 18.4.3 Relocation of assets 325 18.4.4 A way forward? 325 19 Conclusions 329 19.1 Natural Disasters Have Immediate and Protracted Geomorphic Consequences 329 19.2 Natural Disasters Motivate Predictive Geomorphology 329 19.3 Natural Disasters Disturb Sediment Fluxes 330 19.4 Geomorphology of Anthropocenic Disasters 331 References 332 20 Glossary 333