Tim R. Davies
University of Cantebury
New Zealand
Oliver Korup
Universität Potsdam
Germany
John J. Clague
Simon Fraser University
Canada
This Work is a co-publication of the American Geophysical Union and John Wiley and Sons Ltd.
This Work is a co-publication between the American Geophysical Union and John Wiley & Sons Ltd.
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Library of Congress Cataloging-in-Publication Data
Names: Davies, Tim R., 1970- author. | Korup, Oliver, author. | Clague, John, J., author.
Title: Geomorphology and Natural Hazards : Understanding Landscape Change for Disaster Mitigation / Tim R. Davies, Oliver Korup, John J. Clague
Description: First edition. | Hoboken, NJ : Wiley-American Geophysical Union, 2021. | Series: Advanced Textbook Series | Includes bibliographical references and index. | Description based on print version record and CIP data provided by publisher; resource not viewed.
Identifiers: LCCN 2020024258 (print) | LCCN 2020024259 (ebook) | ISBN 9781118648605 (epub) | ISBN 9781118648612 (adobe pdf) | ISBN 9781119990314 (paperback) |
Subjects: LCSH: Natural disasters–Research. | Geomorphology.
Classification: LCC GB5005 (ebook) | LCC GB5005 D38 2021 (print) | DDC 363.34–dc23
LC record available at https://lccn.loc.gov/2020024258 LC record available at https://lccn.loc.gov/2020024259
Cover Design: Wiley
Cover Image: Landslide in Cusco, Peru, 2018
Ministerio de Defensa del Perú (CC BY 2.0)
In spite of ever-increasing research into natural hazards, the reported damage from naturally-triggered continues to rise, increasingly disrupting human activities. We, as scientists who study the way in which the part of Earth most relevant to society—the surface—behaves, are disturbed and frustrated by this trend. It appears that the large amounts of funding devoted each year to research into reducing the impacts of natural disasters could be much more effective in producing useful results. At the same time we are aware that society, as represented by its decision makers, while increasingly concerned at the impacts of natural disasters on lives and economies, is reluctant to acknowledge the intrinsic activity of Earth's surface and to take steps to adapt societal behaviour to minimise the impacts of natural disasters. Understanding and managing natural hazards and disasters are beyond matters of applied earth science, and also involve considering human societal, economic and political decisions.
In this book we attempt to address this multidisciplinary problem directly, based on our experiences in earth science, and also in attempting to apply earth science to hazard and risk management in real-life situations. We acknowledge that other books offer exhaustive material on natural hazards and disasters, or manuals on integrated risk management. We recommend these alternatives for learning the basics about the many natural processes that may cause harm to human activity. Also, the breadth of textbooks devoted to specific natural hazards such as earthquakes, volcanoes, landslides, or floods motivates us to recapitulate only briefly key points from these works, while allowing us to focus more on their geomorphic consequences and implications. The same applies for the theoretical basics of geomorphological processes that are the focus of this book. Instead, we examine many practical issues that arise when dealing with potentially damaging geomorphic processes as a direct or indirect consequence of natural disasters. We choose this avenue because we feel that current textbooks on natural hazards and disasters fail to adopt a holistic and general focus. We find that little synthesised material comprehensively addresses geomorphic hazards and risks, and their mitigation.
Traditionally, and still to a large extent today, hazard management consists of constructing physical works or structural countermeasures to modify the troublesome and potentially destructive processes that operate at Earth's surface. The engineering profession is tasked with the design and construction of these works. Engineering—and in particular hazards engineering—is essentially a societal profession, in that engineers carry out their work in the service of society. When society is threatened or damaged by a natural event, engineers are paid to solve the problem so that societal activity can, as much as possible, continue uninterrupted and unchanged. For millennia, during which low human population levels meant overall lower levels of risk, the vulnerability and adaptive capacity of society to natural hazards may have been different. Still, engineering was dramatically successful in mitigating hazards: floodplains were drained, channelised, and settled; sea-walls kept extreme tides from inundating coastal flats; and river control works channelised sediment across inhabited fans.
Today this situation is changing markedly. Human numbers are continuously increasing and our species is increasingly modifying the planet's surface. Society is becoming increasingly complex and sophisticated and thus less able to adjust its behaviour; economic pressures reduce wasteful system redundancy; and society increasingly—and justifiably—expects the money it spends on risk reduction to protect it from disasters. Whether contemporary climate change is the dominant driver of the observed increase in disaster costs is unclear, but it is certainly a potentially important factor that is some extent also the result of human activity. It is clear that traditional hazard management strategies have become inadequate, and their adequacy will decrease further into the future. A key element of this situation is that society now is expanding into areas for which we have little or unreliable knowledge about the rates of geomorphic processes. These areas may be prone to large and commensurately rare events that, owing to their rarity, are less well described and understood than their more moderate and familiar counterparts. Such events are more powerful and harder to design against, so the reliability of engineering countermeasures is reduced, which must eventually lead to an increase in disasters.
In this book we go beyond the view that natural hazards and disasters have adverse implications for human assets by definition. We argue that understanding the forms and processes of Earth's surface—encapsulated in the science of geomorphology—is essential to assess natural hazards and gauge the consequences of natural disasters on Earth's surface. These consequences involve the often rapid erosion, transport, and deposition of rock debris, soil, biomass, human waste, nutrients, and pathogens, thereby changing or setting the boundary conditions for subsequent hazardous processes. We call for a more detailed view on natural disasters by identifying those processes in a chain of harmful events that produce most damage. Often we find that most damage by earthquakes or storms, for example, is due to landslides instead of seismic shaking or intensive rainfall. By doing so we acknowledge that Earth is an intrinsically active—and therefore hazardous—planet. Occasional intense events that disturb Earth's surface are inevitable, and if society ignores such events, natural disasters and catastrophes will inevitably and repeatedly happen.
We acknowledge that there must be a physical limit to the intensity of a given surface event that can be controlled reliably by engineering works, and therefore suggest that structural works stay within those limits. We particularly underline several lines of empirical evidence and reasons that show that structural interventions may make a disaster-prone situation worse. We also argue that in many situations an extraordinarily large or severe event, although unlikely, can happen, thus both procedures and structures must be put in place to reduce the death and damage that this event can cause. This last point is crucial and fundamental: the extreme events of nature cannot be controlled, but they can be avoided in some cases, and their negative consequences reduced in many cases. Therefore, to reduce the impacts of such events, society must adapt so that their damage is reduced to acceptable levels. This is our key message.
In pointing out some limitations of traditional engineering approaches to control hazards, we refrain from denigrating the engineering profession. One of us was trained and has practised as an engineer, and we understand and sympathise with the aspirations of engineering to improve the lot of society. Nevertheless, we encourage the engineering profession to seek to know and understand its limitations, and we encourage engineers and geomorphologists to understand how they can interact with each other, and with society, to provide better information on threatening events and the options available to manage the threats.
Acknowledging that natural hazards are by definition estimates that involve uncertainty requires that society wilfully adjust its behaviour to nature's. This, in turn, requires that natural systems be adequately known. We must be able to foresee what sizes and types of surface changes can potentially harm human assets (including our natural environment). And we need to know how to make that information available and useful to society. Whether, or to what extent, society acts on that knowledge depends on its nature and aspirations. We are uninformed, except through experience, about the nature and aspirations of society, but recognising that society does have a nature and aspirations is crucial to the way that information is acquired and presented.
In attempting to reduce the impact of hazardous surface processes, we must recognise that two systems interact to create a disaster: the powerful and complex surface geological processes of Earth; and the less powerful but also complex human system, which operates through society and occupies Earth's surface. We have only limited control over nature, and especially over its rare and highly energetic processes. However, we increasingly understand the rules by which the natural system operates, even though that understanding could lead more often to better predictions. In contrast, we have in principle a measure of control over the human system, although we have little understanding of its operation in social, cultural, political and economic terms. However, we believe that by approaching the problem from an applied geomorphological perspective, we can shed some light on what can and cannot be achieved in the way of hazard mitigation and disaster reduction in a range of situations in the future. Whether society has the will to respond to this illumination is beyond our influence, but we sincerely hope that, if future disasters are considered in terms of the concepts we set out herein, illumination might give rise to realisation, acceptance and ultimately action.
Reading through several thousand scientific publications to collect material for a book seems like a futile task in a time of rapidly increasing publication numbers. Deciding which publications to include here was tough, as was keeping track with the many new natural disasters that occurred when we were writing this book. By the time you are reading this book, many of the numbers, especially those concerning projections and predictions, will most likely have changed with new research results arriving, refining, or perhaps even refuting previous work. While you may find parts of this book outdated, perhaps consider it instead as a document of how swiftly our scientific understanding of the vibrant field of geomorphic footprints of natural hazards and disasters changes. At the very least, we hope that the contents of this book distill some of the more persistent findings that a solid understanding of the geomorphic footprints of natural hazards and disasters rests on.
We acknowledge all the hard work that researchers have carried out to better understand natural hazards and to reduce the risks from natural disasters. We have also been involved with many communities, government officials, scientists, technologists, planners, and people affected over several decades in hazard assessment and planning to mitigate disasters. We have learned much from these interactions, and express our gratitude to all involved.