Floods, whether measured in terms of the direct damage to infrastructure, losses to economy or the toll on human health, remain some of the costliest natural disasters in the world. Engineers and other scientists have historically attempted to analyze risk using available historic data and accepted statistical methods. This approach implicitly assumes that past climate conditions will persist within the time frame of interest. Recent flood events worldwide challenge this conceptual approach.
More recently, hydrologic and hydraulic modelling have developed to the point where they have become viable tools to simulate flow events. Whatever method is applied to estimate flood magnitude, there is a degree of uncertainty in the estimate and this has become larger as the effects of climate change alter what we have come to accept as regional hydrologic norms, parameters and relationships.
Floods in a changing climate: risk management is the fourth in a collection of four books on flood disaster management, theory and practice within the context of anthropogenically induced climate change. This book provides approaches to evaluate flood risk in a more systematic manner than is generally employed, and also provides approaches to factor the uncertainty of climate change into the evaluation of flood risk management in a rational and conservative manner. The book has also been structured so that it can be used as the basis for an undergraduate course on the subject of risk management, with example questions at the end of chapters.
The book is logically structured into four main sections, with the first being “Setting the stage” which provides a good background to the subject, Part II and Part III being approaches to analysis and Part IV wrapping up with “Future perspectives”.
The first chapter of Part I is a primer on the subject of flood risk management. The essential concepts in this chapter would be informative for any politician or bureaucrat responsible for flood management. The issue of flood management is put into a worldwide context including striking examples of past disasters. It also provides sobering statistics on the increasing frequency of flood events, cost of damages and increases in the number of deaths over the last half century. The second chapter opens by reviewing the primary mechanisms generating floods around the world, so that the potential impact of climate change can be presented in an adequate context. Although this is a cursory examination of a complex topic, it provides an adequate basis for introducing the potential impacts of man’s impact on runoff processes and, ultimately, world climate. The second chapter also describes the current state of understanding of the potential impacts of climate change and introduces mitigation and adaptation as potential approaches for managing climate change impact, especially in the context of flooding. The third chapter introduces the concept of flood risk management as an adaptation strategy to climate change impacts. This chapter clearly lays out a systematic process for evaluating risk and introduces two methods to incorporate the uncertainty of climate change into the risk analysis. The inclusion of a case study for the city of London, Ontario, helps to illustrate how to perform a risk analysis and build likely climate change scenarios into the analysis.
Parts II and III (Chapters 4 and 5) provide approaches for identifying, assessing and prioritizing climate-related risks. Rigorous assessment is employed to determine the available probabilistic and fuzzy set-based analytic tools, when each is appropriate and how to apply them to practical problems. These chapters require careful reading and thought on the part of the reader as some advanced analytical concepts are provided. Chapter 4 presents a probabilistic approach that is an extension of the conventional statistical hydrology approach used by most agencies in flood management policy.
For example, it is common to state that flood protection was designed for the “100-year flood event”. In the view of most members of the public, this should mean that flooding should only occur every 100 years in the long term. The concepts of probability and risk are explained and the author provides simple tables to put this into perspective from a risk management standpoint. This allows the reader to easily identify that there is almost a 40% chance of the “100-year” design being exceeded in the next 50 years, even before taking into consideration the potential impact of climate change. The remainder of Part II provides practical analyses to refine the probabilistic approach to defining risk to account for probable climate change impacts.
Part III introduces the “fuzzy set approach” (FSA) to analysing aspects of flood risk or risk management approaches. Probability theory arises from the question of whether or not an event occurs and uses observations and standardized statistical approaches to define the likelihood of future events occurring. In contrast, FSA is described as a type of deterministic uncertainty that measures the degree to which an event occurs and not whether it occurs. Three sets of tools that use fuzzy sets are presented. The author believes that the application of FSA can improve the climate change-related decision-making process in situations where the goals, constraints and consequences are not precisely known.
Part IV provides a fitting conclusion to the book by providing some perspective on the future and how flood risk management must change as our understanding (or lack of understanding) about climate change is acknowledged and built into the process.
Professionals and policy-makers working in hazard mitigation, water resources engineering and environmental economics will find this an invaluable resource even if they struggle (as I did) through some of the more advanced concepts of fuzzy logic. This will also be very useful to the next generation of decision-makers if it can be introduced into the academic curriculum in the fields of hydrology, climate change, environmental science or policy, and risk assessment.
Golder Associates, Winnipeg, Manitoba
© 2014 Canadian Water Resources Association
http://dx.doi.org/10.1080/07011784.2014.942114