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Assessment and Adaptation to Climate Change-Related Flood Risks  

Brenden Jongman, Hessel C. Winsemius, Stuart A. Fraser, Sanne Muis, and Philip J. Ward

The flooding of rivers and coastlines is the most frequent and damaging of all natural hazards. Between 1980 and 2016, total direct damages exceeded $1.6 trillion, and at least 225,000 people lost their lives. Recent events causing major economic losses include the 2011 river flooding in Thailand ($40 billion) and the 2013 coastal floods in the United States caused by Hurricane Sandy (over $50 billion). Flooding also triggers great humanitarian challenges. The 2015 Malawi floods were the worst in the country’s history and were followed by food shortage across large parts of the country. Flood losses are increasing rapidly in some world regions, driven by economic development in floodplains and increases in the frequency of extreme precipitation events and global sea level due to climate change. The largest increase in flood losses is seen in low-income countries, where population growth is rapid and many cities are expanding quickly. At the same time, evidence shows that adaptation to flood risk is already happening, and a large proportion of losses can be contained successfully by effective risk management strategies. Such risk management strategies may include floodplain zoning, construction and maintenance of flood defenses, reforestation of land draining into rivers, and use of early warning systems. To reduce risk effectively, it is important to know the location and impact of potential floods under current and future social and environmental conditions. In a risk assessment, models can be used to map the flow of water over land after an intense rainfall event or storm surge (the hazard). Modeled for many different potential events, this provides estimates of potential inundation depth in flood-prone areas. Such maps can be constructed for various scenarios of climate change based on specific changes in rainfall, temperature, and sea level. To assess the impact of the modeled hazard (e.g., cost of damage or lives lost), the potential exposure (including buildings, population, and infrastructure) must be mapped using land-use and population density data and construction information. Population growth and urban expansion can be simulated by increasing the density or extent of the urban area in the model. The effects of floods on people and different types of buildings and infrastructure are determined using a vulnerability function. This indicates the damage expected to occur to a structure or group of people as a function of flood intensity (e.g., inundation depth and flow velocity). Potential adaptation measures such as land-use change or new flood defenses can be included in the model in order to understand how effective they may be in reducing flood risk. This way, risk assessments can demonstrate the possible approaches available to policymakers to build a less risky future.


Evolution of Strategic Flood Risk Management in Support of Social Justice, Ecosystem Health, and Resilience  

Paul Sayers

Throughout history, flood management practice has evolved in response to flood events. This heuristic approach has yielded some important incremental shifts in both policy and planning (from the need to plan at a catchment scale to the recognition that flooding arises from multiple sources and that defenses, no matter how reliable, fail). Progress, however, has been painfully slow and sporadic, but a new, more strategic, approach is now emerging. A strategic approach does not, however, simply sustain an acceptable level of flood defence. Strategic Flood Risk Management (SFRM) is an approach that relies upon an adaptable portfolio of measures and policies to deliver outcomes that are socially just (when assessed against egalitarian, utilitarian, and Rawlsian principles), contribute positively to ecosystem services, and promote resilience. In doing so, SFRM offers a practical policy and planning framework to transform our understanding of risk and move toward a flood-resilient society. A strategic approach to flood management involves much more than simply reducing the chance of damage through the provision of “strong” structures and recognizes adaptive management as much more than simply “wait and see.” SFRM is inherently risk based and implemented through a continuous process of review and adaptation that seeks to actively manage future uncertainty, a characteristic that sets it apart from the linear flood defense planning paradigm based upon a more certain view of the future. In doing so, SFRM accepts there is no silver bullet to flood issues and that people and economies cannot always be protected from flooding. It accepts flooding as an important ecosystem function and that a legitimate ecosystem service is its contribution to flood risk management. Perhaps most importantly, however, SFRM enables the inherent conflicts as well as opportunities that characterize flood management choices to be openly debated, priorities to be set, and difficult investment choices to be made.


Hazards, Social Resilience, and Safer Futures  

Lena Dominelli

The concepts of hazards and risks began in engineering when scientists were measuring the points at which materials would become sufficiently stressed by the pressures upon them that they would break. These concepts migrated into the environmental sciences to assess risk in the natural terrain, including the risks that human activities posed to the survival of animals (including fish in streams) and plants in the biosphere. From there, they moved to the social sciences, primarily in formal disaster discourses. With the realization that modern societies constantly faced risks cushioned in uncertainties within everyday life, the media popularized the concept of risk and its accoutrements, including mitigation, adaptation, and preventative measures, among the general populace. A crucial manifestation of this is the media’s accounts of the risks affecting different groups of people or places contracting Covid-19, which burst upon a somnambulant world in December 2019 in Wuhan, China. The World Health Organization (WHO) declared Covid-19 a pandemic on March 11, 2020. Politicians of diverse hues sought to reassure nervous inhabitants that they had followed robust, scientific advice on risks to facilitate “flattening the curve” by spreading the rate of infection in different communities over a longer period to reduce demand for public health services. Definitions of hazard, risk, vulnerability, and resilience evolved as they moved from the physical sciences into everyday life to reassure edgy populations that their social systems, especially the medical ones, could cope with the demands of disasters. While most countries have managed the risk Covid-19 posed to health services, this has been at a price that people found difficult to accept. Instead, as they reflected upon their experiences of being confronted with the deaths of many loved ones, especially among elders in care homes; adversities foisted upon the disease’s outcomes by existing social inequalities; and loss of associative freedoms, many questioned whether official mitigation strategies were commensurate with apparent risks. The public demanded an end to such inequities and questioned the bases on which politicians made their decisions. They also began to search for certainties in the social responses to risk in the hopes of building better futures as other institutions, schools, and businesses went into lockdown, and social relationships and people’s usual interactions with others ceased. For some, it seemed as if society were crumbling around them, and they wanted a better version of their world to replace the one devastated by Covid-19 (or other disasters). Key to this better version was a safer, fairer, more equitable and reliable future. Responses to the risks within Covid-19 scenarios are similar to responses to other disasters, including earthquakes, volcanic eruptions, wildfires, tsunamis, storms, extreme weather events, and climate change. The claims of “building back better” are examined through a resilience lens to determine whether such demands are realizable, and if not, what hinders their realization. Understanding such issues will facilitate identification of an agenda for future research into mitigation, adaptation, and preventative measures necessary to protect people and the planet Earth from the harm of subsequent disasters.


Megacity Disaster Risk Governance  

James K. Mitchell

Megacity disaster risk governance is a burgeoning interdisciplinary field that seeks to encourage improved public decision-making about the safety and sustainability of the world’s largest urban centers in the face of environmental threats ranging from floods, storms, earthquakes, wildfires, and pandemics to the multihazard challenges posed by human-forced climate change. It is a youthful, lively, contested, ambitious and innovative endeavor that draws on research in three separate but overlapping areas of inquiry: disaster risks, megacities, and governance. Toward the end of the 20th century, each of these fields underwent major shifts in thinking that opened new possibilities for action. First, the human role in disaster risks came to the fore, giving increased attention to humans as agents of risk creation and providing increased scope for inputs from social sciences and humanities. Second, the scale, complexity, and political–economic salience of very large cities attained high visibility, leading to recognition that they are also sites of unprecedented risks, albeit with significant differences between rapidly growing poorer cities and slower growing affluent ones. Third, the concept of public decision-making expanded beyond its traditional association with actions of governments to include contributions from a wide range of nongovernmental groups that had not previously played prominent roles in public affairs. At least three new conceptions of megacity disaster risk governance emerged out of these developments. They include adaptive risk governance, smart city governance, and aesthetic governance. Adaptive risk governance focuses on capacities of at-risk communities to continuously adjust to dynamic uncertainties about future states of biophysical environments and human populations. It is learning-centered, collaborative, and nimble. Smart city governance seeks to harness the capabilities of new information and communication technologies, and their associated human institutions, to the increasingly automated tasks of risk anticipation and response. Aesthetic governance privileges the preferences of social, scientific, design, or political elites and power brokers in the formulation and execution of policies that bear on risks. No megacity has yet comprehensively or uniformly adopted any of these risk governance models, but many are experimenting with various permutations and hybrid variations that combine limited applications with more traditional administrative practices. Arrangements that are tailor-made to fit local circumstances are the norm. However, some version of adaptive risk governance seems to be the leading candidate for wider adoption, in large part because it recognizes the need to continuously accommodate new challenges as environments and societies change and interact in ways that are difficult to predict. Although inquiries are buoyant, there remain many unanswered questions and unaddressed topics. These include the differential vulnerability of societal functions that are served by megacities and appropriate responses thereto; the nature and biases of risk information transfers among different types of megacities; and appropriate ways of tackling ambiguities that attend decision-making in megacities. Institutions of megacity disaster risk governance will take time to evolve. Whether that process can be speeded up and applied in time to stave off the worst effects of the risks that lie ahead remains an open question.