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Article

David Proverbs and Jessica Lamond

Flood resilient construction has become an essential component of the integrated approach to flood risk management, now widely accepted through the concepts of making space for water and living with floods. Resilient construction has been in place for centuries, but only fairly recently has it been recognized as part of this wider strategy to manage flood risk. Buildings and the wider built environment are known to play a key role in flood risk management, and when buildings are constructed on or near to flood plains there is an obvious need to protect these. Engineered flood defense systems date back centuries, with early examples seen in China and Egypt. Levees were first built in the United States some 150 years ago, and were followed by the development of flood control acts and regulations. In 1945, Gilbert Fowler White, the so-called “father of floodplain management,” published his influential thesis which criticized the reliance on engineered flood defenses and began to change these approaches. In Europe, a shortage of farmable land led to the use of land reclamation schemes and the ensuing Land Drainage acts before massive flood events in the mid-20th century led to a shift in thinking towards the engineered defense schemes such as the Thames Barrier and Dutch dyke systems. The early 21st century witnessed the emergence of the “living with water” philosophy, which has resulted in the renewed understanding of flood resilience at a property level. The scientific study of construction methods and building technologies that are robust to flooding is a fairly recent phenomenon. There are a number of underlying reasons for this, but the change in flood risk philosophy coupled with the experience of flood events and the long process of recovery is helping to drive research and investment in this area. This has led to a more sophisticated understanding of the approaches to avoiding damage at an individual property level, categorized under three strategies, namely avoidance technology, water exclusion technology, and water entry technology. As interest and policy has shifted to water entry approaches, alongside this has been the development of research into flood resilient materials and repair and reinstatement processes, the latter gaining much attention in the recognition that experience will prompt resilient responses and that the point of reinstatement provides a good opportunity to install resilient measures. State-of-the-art practices now center on avoidance strategies incorporating planning legislation in many regions to prohibit or restrict new development in flood plains. Where development pressures mean that new buildings are permitted, there is now a body of knowledge around the impact of flooding on buildings and flood resilient construction and techniques. However, due to the variety and complexity of architecture and construction styles and varying flood risk exposure, there remain many gaps in our understanding, leading to the use of trial and error and other pragmatic approaches. Some examples of avoidance strategies include the use of earthworks, floating houses, and raised construction. The concept of property level flood resilience is an emerging concept in the United Kingdom and recognizes that in some cases a hybrid approach might be favored in which the amount of water entering a property is limited, together with the likely damage that is caused. The technology and understanding is moving forward with a greater appreciation of the benefits from combining strategies and property level measures, incorporating water resistant and resilient materials. The process of resilient repair and considerate reinstatement is another emerging feature, recognizing that there will be a need to dry, clean, and repair flood-affected buildings. The importance of effective and timely drying of properties, including the need to use materials that dry rapidly and are easy to decontaminate, has become more apparent and is gaining attention. Future developments are likely to concentrate on promoting the uptake of flood resilient materials and technologies both in the construction of new and in the retrofit and adaptation of existing properties. Further development of flood resilience technology that enhances the aesthetic appeal of adapted property would support the uptake of measures. Developments that reduce cost or that offer other aesthetic or functional advantages may also reduce the barriers to uptake. A greater understanding of performance standards for resilient materials will help provide confidence in such measures and support uptake, while further research around the breathability of materials and concerns around mold and the need to avoid creating moisture issues inside properties represent some of the key areas.

Article

Marian Muste and Ton Hoitink

With a continuous global increase in flood frequency and intensity, there is an immediate need for new science-based solutions for flood mitigation, resilience, and adaptation that can be quickly deployed in any flood-prone area. An integral part of these solutions is the availability of river discharge measurements delivered in real time with high spatiotemporal density and over large-scale areas. Stream stages and the associated discharges are the most perceivable variables of the water cycle and the ones that eventually determine the levels of hazard during floods. Consequently, the availability of discharge records (a.k.a. streamflows) is paramount for flood-risk management because they provide actionable information for organizing the activities before, during, and after floods, and they supply the data for planning and designing floodplain infrastructure. Moreover, the discharge records represent the ground-truth data for developing and continuously improving the accuracy of the hydrologic models used for forecasting streamflows. Acquiring discharge data for streams is critically important not only for flood forecasting and monitoring but also for many other practical uses, such as monitoring water abstractions for supporting decisions in various socioeconomic activities (from agriculture to industry, transportation, and recreation) and for ensuring healthy ecological flows. All these activities require knowledge of past, current, and future flows in rivers and streams. Given its importance, an ability to measure the flow in channels has preoccupied water users for millennia. Starting with the simplest volumetric methods to estimate flows, the measurement of discharge has evolved through continued innovation to sophisticated methods so that today we can continuously acquire and communicate the data in real time. There is no essential difference between the instruments and methods used to acquire streamflow data during normal conditions versus during floods. The measurements during floods are, however, complex, hazardous, and of limited accuracy compared with those acquired during normal flows. The essential differences in the configuration and operation of the instruments and methods for discharge estimation stem from the type of measurements they acquire—that is, discrete and autonomous measurements (i.e., measurements that can be taken any time any place) and those acquired continuously (i.e., estimates based on indirect methods developed for fixed locations). Regardless of the measurement situation and approach, the main concern of the data providers for flooding (as well as for other areas of water resource management) is the timely delivery of accurate discharge data at flood-prone locations across river basins.

Article

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.

Article

Jason Thistlethwaite and Daniel Henstra

Natural hazards are a complex governance problem. Managing the risks associated with natural hazards requires action at all scales—from household to national—but coordinating these nested responses to achieve a vertically cohesive course of action is challenging. Moreover, though governments have the legal authority and legitimacy to mandate or facilitate natural hazard risk reduction, non-governmental actors such as business firms, industry associations, research organizations and non-profit organizations hold much of the pertinent knowledge and resources. This interdependence demands horizontal collaboration, but coordinating risk reduction across organizational divides is fraught with challenges and requires skillful leadership. Flood risk management (FRM)—an integrated strategy to reduce the likelihood and impacts of flooding—demonstrates the governance challenge presented by natural hazards. By engaging stakeholders, coordinating public and private efforts, and employing a diversity of policy instruments, FRM can strengthen societal resilience, achieve greater efficiency, and enhance the legitimacy of decisions and actions to reduce flood risk. Implementing FRM, however, requires supportive flood risk governance arrangements that facilitate vertical and horizontal policy coordination by establishing strategic goals, negotiating roles and responsibilities, aligning policy instruments, and allocating resources.

Article

Anna Murgatroyd and Simon Dadson

Flooding is a natural hazard with the potential to cause damage at the local, national, and global scale. Flooding is a natural product of heavy precipitation and increased runoff. It may also arise from elevated groundwater tables, coastal inundation, or failed drainage systems. Flooded areas can be identified as land beyond the channel network covered by water. Although flooding can cause significant damage to urban developments and infrastructure, it may be beneficial to the natural environment. Preemptive actions may be taken to protect communities at risk of inundation that are not able to relocate to an area not at risk of flooding. Adaptation measures include flood defenses, river channel modification, relocation, and active warning systems. Natural flood management (NFM) interventions are designed to restore, emulate, or enhance catchment processes. Such interventions are common in upper reaches of the river and in areas previously transformed by agriculture and urban development. Natural techniques can be categorized into three groups: water retention through management of infiltration and overland flow, managing channel connectivity and conveyance, and floodplain conveyance and storage. NFM may alter land use, improve land management, repair river channel morphology, enhance the riparian habitat, enrich floodplain vegetation, or alter land drainage. The range of natural flood management options allows a diverse range of flood hazards to be considered. As a consequence, there is an abundance of NFM case studies from contrasting environments around the globe, each addressing a particular set of flood risks. Much of the research supporting the use of NFM highlights both the benefits and costs of working with natural processes to reduce flood hazards in the landscape. However, there is a lack of quantitative evidence of the effectiveness of measures, both individually and in combination, especially at the largest scales and for extreme floods. Most evidence is based on modeling studies and observations often relate to a specific set of upstream measures that are challenging to apply elsewhere.

Article

Humankind is becoming increasingly dependent on timely flood warnings. Dependence is being driven by an increasing frequency and intensity of heavy rainfall events, a growing number of disruptive and damaging floods, and rising sea levels associated with climate change. At the same time, the population living in flood-risk areas and the value of urban and rural assets exposed to floods are growing rapidly. Flood warnings are an important means of adapting to growing flood risk and learning to live with it by avoiding damage, loss of life, and injury. Such warnings are increasingly being employed in combination with other flood-risk management measures, including large-scale mobile flood barriers and property-level protection measures. Given that lives may well depend on effective flood warnings and appropriate warning responses, it is crucial that the warnings perform satisfactorily, particularly by being accurate, reliable, and timely. A sufficiently long warning lead time to allow precautions to be taken and property and people to be moved out of harm’s way is particularly important. However, flood warnings are heavily dependent on the other components of flood forecasting, warning, and response systems of which they are a central part. These other components—flood detection, flood forecasting, warning communication, and warning response—form a system that is characterized as a chain, each link of which depends on the other links for effective outcomes. Inherent weaknesses exist in chainlike processes and are often the basis of warning underperformance when it occurs. A number of key issues confront those seeking to create and successfully operate flood warning systems, including (1) translating technical flood forecasts into warnings that are readily understandable by the public; (2) taking legal responsibility for warnings and their dissemination; (3) raising flood-risk awareness; (4) designing effective flood warning messages; (5) knowing how best and when to communicate warnings; and (6) addressing uncertainties surrounding flood warnings. Flood warning science brings together a large body of research findings from a particularly wide range of disciplines ranging from hydrometeorological science to social psychology. In recent decades, major advances have been made in forecasting fluvial and coastal floods. Accurately forecasting pluvial events that cause surface-water floods is at the research frontier, with significant progress being made. Over the same time period, impressive advances in a variety of rapid, personalized communication means has transformed the process of flood warning dissemination. Much is now known about the factors that constrain and aid appropriate flood warning responses both at the individual and at organized, flood emergency response levels, and a range of innovations are being applied to improve response effectiveness. Although the uniqueness of each flood and the inherent unpredictability involved in flood events means that sometimes flood warnings may not perform as expected, flood warning science is helping to minimize these occurrences.

Article

Flooding remains one of the globe’s most devastating natural hazards and a leading driver of natural disaster losses across many countries, including the United States. As such, a rich and growing literature aims to better understand, model, and assess flood losses. Several major theoretical and empirical themes emerge from the literature. Fundamental to the flood damage assessment literature are definitions of flood damage, including a typology of flood damage, such as direct and indirect losses. In addition, the literature theoretically and empirically assesses major determinants of flood damage including hydrological factors, measurement of the physical features in harm’s way, as well as understanding and modeling protective activities, such as flood risk mitigation and adaptation, that all co-determine the overall flood losses. From there, common methods to quantify flood damage take these factors as inputs, modeling hydrological risk, exposure, and vulnerability into quantifiable flood loss estimates through a flood damage function, and include both ex ante expected loss assessments and ex post event-specific analyses. To do so, high-quality data are key across all model steps and can be found across a variety of sources. Early 21st-century advancements in spatial data and remote sensing push the literature forward. While topics and themes apply more generally to flood damage across the globe, examples from the United States illustrate key topics. Understanding main themes and insights in this important research area is critical for researchers, policy-makers, and practitioners to better understand, utilize, and extend existing flood damage assessment literatures in order to lessen or even prevent future tragedy.

Article

The rapid increase in losses from flooding underlines the importance of risk reduction efforts to prevent or at least mitigate the damaging impacts that floods can bring to communities, businesses, and countries. This article provides an overview of how the science of disaster risk management has improved understanding of pre-event risk reduction [or disaster risk reduction (DRR)]. Implementation, however, is still lagging, particularly when compared to expenditure for recovery and repair after a flood event. In response, flood insurance is increasingly being suggested as a potential lever for risk reduction, despite concerns about moral hazard. The article considers the literature that has emerged on this topic and discusses if the conceptual efforts of linking flood insurance and risk reduction have led to practical action. Overall, there is limited evidence of flood insurance effectively promoting risk reduction. To the extent there is, it suggests that more complex behavioral aspects are also at play. Further evidence is required to support this potential role, particularly around data and risk assessment, and the viability of different risk reduction measures.

Article

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.

Article

Bruno Merz

Floods affect more people worldwide than any other natural hazard. Flood risk results from the interplay of a range of processes. For river floods, these are the flood-triggering processes in the atmosphere, runoff generation in the catchment, flood waves traveling through the river network, possibly flood defense failure, and finally, inundation and damage processes in the flooded areas. In addition, ripple effects, such as regional or even global supply chain disruptions, may occur. Effective and efficient flood risk management requires understanding and quantifying the flood risk and its possible future developments. Hence, risk analysis is a key element of flood risk management. Risk assessments can be structured according to three questions: What can go wrong? How likely is it that it will happen? If it goes wrong, what are the consequences? Before answering these questions, the system boundaries, the processes to be included, and the detail of the analysis need to be carefully selected. One of the greatest challenges in flood risk analyses is the identification of the set of failure or damage scenarios. Often, extreme events beyond the experience of the analyst are missing, which may bias the risk estimate. Another challenge is the estimation of probabilities. There are at most a few observed events where data on the flood situation, such as inundation extent, depth, and loss are available. That means that even in the most optimistic situation there are only a few data points to validate the risk estimates. The situation is even more delicate when the risk has to be quantified for important infrastructure objects, such as breaching of a large dam or flooding of a nuclear power plant. Such events are practically unrepeatable. Hence, estimating of probabilities needs to be based on all available evidence, using observations whenever possible, but also including theoretical knowledge, modeling, specific investigations, experience, or expert judgment. As a result, flood risk assessments are often associated with large uncertainties. Examples abound where authorities, people at risk, and disaster management have been taken by surprise due to unexpected failure scenarios. This is not only a consequence of the complexity of flood risk systems, but may also be attributed to cognitive biases, such as being overconfident in the risk assessment. Hence, it is essential to ask: How wrong can the risk analysis be and still guarantee that the outcome is acceptable?

Article

Gabriele Villarini and Louise Slater

Flood losses in the United States have increased dramatically over the course of the past century, averaging US$7.96 billion in damages per year for the 30-year period ranging from 1985 to 2014. In terms of human fatalities, floods are the second largest weather-related hazard in the United States, causing approximately 80 deaths per year over the same period. Given the wide-reaching impacts of flooding across the United States, the evaluation of flood-generating mechanisms and of the drivers of changing flood hazard are two areas of active research. Flood frequency analysis has traditionally been based on statistical analyses of the observed flood distributions that rarely distinguish among physical flood-generating processes. However, recent scientific advances have shown that flood frequency distributions are often characterized by “mixed populations” arising from multiple flood-generating mechanisms, which can be challenging to disentangle. Flood events can be driven by a variety of physical mechanisms, including rain and snowmelt, frontal systems, monsoons, intense tropical cyclones, and more generic cyclonic storms. Temporal changes in the frequency and magnitude of flooding have also been the subject of a large body of work in recent decades. The science has moved from a focus on the detection of trends and shifts in flood peak distributions towards the attribution of these changes, with particular emphasis on climatic and anthropogenic factors, including urbanization and changes in agricultural practices. A better understanding of these temporal changes in flood peak distributions, as well as of the physical flood-generating mechanisms, will enable us to move forward with the estimation of future flood design values in the context of both climatic and anthropogenic change.

Article

Communities facing urban flood risk have access to powerful flood simulation software for use in disaster-risk-reduction (DRR) initiatives. However, recent research has shown that flood risk continues to escalate globally, despite an increase in the primary outcome of flood simulation: increased knowledge. Thus, a key issue with the utilization of urban flood models is not necessarily development of new knowledge about flooding, but rather the achievement of more socially robust and context-sensitive knowledge production capable of converting knowledge into action. There are early indications that this can be accomplished when an urban flood model is used as a tool to bring together local lay and scientific expertise around local priorities and perceptions, and to advance improved, target-oriented methods of flood risk communication. The success of urban flood models as a facilitating agent for knowledge coproduction will depend on whether they are trusted by both the scientific and local expert, and to this end, whether the model constitutes an accurate approximation of flood dynamics is a key issue. This is not a sufficient condition for knowledge coproduction, but it is a necessary one. For example, trust can easily be eroded at the local level by disagreements among scientists about what constitutes an accurate approximation. Motivated by the need for confidence in urban flood models, and the wide variety of models available to users, this article reviews progress in urban flood model development over three eras: (1) the era of theory, when the foundation of urban flood models was established using fluid mechanics principles and considerable attention focused on development of computational methods for solving the one- and two-dimensional equations governing flood flows; (2) the era of data, which took form in the 2000s, and has motivated a reexamination of urban flood model design in response to the transformation from a data-poor to a data-rich modeling environment; and (3) the era of disaster risk reduction, whereby modeling tools are put in the hands of communities facing flood risk and are used to codevelop flood risk knowledge and transform knowledge to action. The article aims to inform decision makers and policy makers regarding the match between model selection and decision points, to orient the engineering community to the varied decision-making and policy needs that arise in the context of DRR activities, to highlight the opportunities and pitfalls associated with alternative urban flood modeling techniques, and to frame areas for future research.

Article

Guy J.-P. Schumann

For about 40 years, with a proliferation over the last two decades, remote sensing data, primarily in the form of satellite and airborne imagery and altimetry, have been used to study floods, floodplain inundation, and river hydrodynamics. The sensors and data processing techniques that exist to derive information about floods are numerous. Instruments that record flood events may operate in the visible, thermal, and microwave range of the electromagnetic spectrum. Due to the limitations posed by adverse weather conditions during flood events, radar (microwave range) sensors are invaluable for monitoring floods; however, if a visible image of flooding can be acquired, retrieving useful information from this is often more straightforward. During recent years, scientific contributions in the field of remote sensing of floods have increased considerably, and science has presented innovative research and methods for retrieving information content from multi-scale coverages of disastrous flood events all over the world. Progress has been transformative, and the information obtained from remote sensing of floods is becoming mature enough to not only be integrated with computer simulations of flooding to allow better prediction, but also to assist flood response agencies in their operations. Furthermore, this advancement has led to a number of recent and upcoming satellite missions that are already transforming current procedures and operations in flood modeling and monitoring, as well as our understanding of river and floodplain hydrodynamics globally. Global initiatives that utilize remote sensing data to strengthen support in managing and responding to flood disasters (e.g., The International Charter, The Dartmouth Flood Observatory, CEOS, NASA’s Servir and the European Space Agency’s Tiger-Net initiatives), primarily in developing nations, are becoming established and also recognized by many nations that are in need of assistance because traditional ground-based monitoring systems are sparse and in decline. The value remote sensing can offer is growing rapidly, and the challenge now lies in ensuring sustainable and interoperable use as well as optimized distribution of remote sensing products and services for science as well as operational assistance.

Article

Giuliano Di Baldassarre

Fatalities and economic losses caused by floods are dramatically increasing in many regions of the world, and there is serious concern about future flood risk given the potentially negative effects of climatic and socio-economic changes. Over the past decades, numerous socio-economic studies have explored human responses to floods—demographic, policy and institutional changes following the occurrence of extreme events. Meanwhile, many hydrological studies have investigated human influences on floods, such as changes in frequency, magnitude, and spatial distribution of floods caused by urbanization or by implementation of risk reduction measures. Research in socio-hydrology is providing initial insights into the complex dynamics of risk resulting from the interplay (both responses and influences) between floods and people. Empirical research in this field has recently shown that traditional methods for flood risk assessment cannot capture the complex dynamics of risk emerging from mutual interactions and continuous feedback mechanisms between hydrological and social processes. It has also been shown that, while risk reduction strategies built on these traditional methods often work in the short term, they might lead to unintended consequences in the longer term. Besides empirical studies, a number of socio-hydrological models have been recently proposed to conceptualize human/flood interactions, to explain the dynamics emerging from this interplay, and to explore possible future trajectories of flood risk. Understanding the interplay between floods and societies can improve our ability to interpret flood risk changes over time and contribute to developing better policies and measures that will reduce the negative impacts of floods while maintaining the benefits of hydrological variability.

Article

In architecture, mitigation reduces the magnitude of climate change by reducing demand for resources; anticipatory adaptation improves performance against hazards; and planned adaptation creates policies and codes to support adaptation. Adaptation prepares for a future with intensifying climate conditions. The built environment must prepare for challenges that may be encountered during the service life of the building, and reduce human exposure to hazards. Structures are responsible for about 39% of the primary energy consumption worldwide and 24% of the greenhouse gas emissions, significantly contributing to the causes of climate change. Measures to reduce demand in the initial construction and over the life cycle of the building operation directly impact the climate. Improving performance against hazards requires a suite of modifications to counter specific threats. Adaptation measures may address higher temperatures, extreme precipitation, stormwater flooding, sea-level rise, hurricanes, drought, soil subsidence, wildfires, extended pest ranges, and multiple hazards. Because resources to meet every threat are inadequate, actions with low costs now which offer high benefits under a range of predicted future climates become high-priority solutions. Disaster risk is also reduced by aligning policies for planning and construction with anticipated hazards. Climate adaptation policies based on the local effects of climate change are a new tool to communicate risk and share resources. Building codes establish minimum standards for construction, so incorporating adaptation strategies into codes ensures that the resulting structures will survive a range of uncertain futures.

Article

Mahesh Prakash, James Hilton, Claire Miller, Vincent Lemiale, Raymond Cohen, and Yunze Wang

Remotely sensed data for the observation and analysis of natural hazards is becoming increasingly commonplace and accessible. Furthermore, the accuracy and coverage of such data is rapidly improving. In parallel with this growth are ongoing developments in computational methods to store, process, and analyze these data for a variety of geospatial needs. One such use of this geospatial data is for input and calibration for the modeling of natural hazards, such as the spread of wildfires, flooding, tidal inundation, and landslides. Computational models for natural hazards show increasing real-world applicability, and it is only recently that the full potential of using remotely sensed data in these models is being understood and investigated. Some examples of geospatial data required for natural hazard modeling include: • elevation models derived from RADAR and Light Detection and Ranging (LIDAR) techniques for flooding, landslide, and wildfire spread models • accurate vertical datum calculations from geodetic measurements for flooding and tidal inundation models • multispectral imaging techniques to provide land cover information for fuel types in wildfire models or roughness maps for flood inundation studies Accurate modeling of such natural hazards allows a qualitative and quantitative estimate of risks associated with such events. With increasing spatial and temporal resolution, there is also an opportunity to investigate further value-added usage of remotely sensed data in the disaster modeling context. Improving spatial data resolution allows greater fidelity in models allowing, for example, the impact of fires or flooding on individual households to be determined. Improving temporal data allows short and long-term trends to be incorporated into models, such as the changing conditions through a fire season or the changing depth and meander of a water channel.

Article

People not only want to be safe from natural hazards; they also want to feel they are safe. Sometimes these two desires pull in different directions, and when they do, this slows the journey to greater physical adaptation and resilience. All people want to feel safe—especially in their own homes. In fact, although not always a place of actual safety, in many cultures “home” is nonetheless idealized as a place of security and repose. The feeling of having a safe home is one part of what is termed ontological security: freedom from existential doubts and the ability to believe that life will continue in much the same way as it always has, without threat to familiar assumptions about time, space, identity, and well-being. By threatening our homes, floods, earthquakes, and similar events disrupt ontological security: they destroy the possessions that support our sense of who we are; they fracture the social structures that provide us with everyday needs such as friendship, play, and affection; they disrupt the routines that give our lives a sense of predictability; and they challenge the myth of our immortality. Such events, therefore, not only cause physical injury and loss; by damaging ontological security, they also cause emotional distress and jeopardize long-term mental health. However, ontological security is undermined not only by the occurrence of hazard events but also by their anticipation. This affects people’s willingness to take steps that would reduce hazard vulnerability. Those who are confident that they can eliminate their exposure to a hazard will usually do so. More commonly, however, the available options come with uncertainty and social/psychological risks: often, the available options only reduce vulnerability, and sometimes people doubt the effectiveness of these options or their ability to choose and implement appropriate measures. In these circumstances, the risk to ontological security that is implied by action can have greater influence than the potential benefits. For example, although installing a floodgate might reduce a business’s flood vulnerability, the business owner might feel that its presence would act as an everyday reminder that the business, and the income derived from it, are not secure. Similarly, bolting furniture to the walls of a home might reduce injuries in the next earthquake, but householders might also anticipate that it would remind them that there is a continual threat to their home. Both of these circumstances describe situations in which the anticipation of future feelings can tap into less conscious anxieties about ontological security. The manner in which people anticipate impacts on ontological security has several implications for preparedness. For example, it suggests that hazard warnings will be counterproductive if they are not accompanied by suggestions of easy, reliable ways of eliminating risk. It also suggests that adaptation measures should be designed not to enhance awareness of the hazard.

Article

Flood Risk Management (FRM) calls for stakeholders from multiple technical and social spheres to plan and implement policies and actions to manage flooding successfully. To work effectively across boundaries of knowledge, practice, priority, scale, institutions, and language created by such interdisciplinary or inter-stakeholder work, it is often necessary to employ intermediaries to create communication pathways between groups and spaces. Intermediaries (also sometimes referred to as mediators or boundary spanners) are responsible for managing boundaries in such a way that multiple actors are able to communicate effectively with limited ambiguity or frustration. Sometimes, intermediaries enable two actors to come together who would usually not interact. For FRM, knowledge and experiences should ideally be brought together collaboratively and smoothly, whilst accounting for the diversity of perspectives and priorities between stakeholders involved. Intermediaries may be organizations of humans, e.g., a public communications department; or objects, e.g., a computer model, website, or maps. Recognizing the utility of objects as intermediaries is important for understanding the multiplicity of mechanisms used to communicate FRM between experts and nonspecialist publics. Charting how intermediaries bridge different boundaries, we see the diversity and utility of their work. Inspecting the construction of boundary objects as intermediaries allows the actors involved in their creation and definition to be identified and analyzed. This is important as it may contribute an understanding of how just and representative FRM decision making is. Since the 1980s, various academic literatures from science and technology studies (STS) to organizational studies have addressed the role of intermediaries and mediators, particularly in relation to business management, computer sciences, and biomedicine. However, in FRM where risk analysis and communication is king, discussing how to manage pertinent and credible transboundary information is also important.

Article

Nigeria, like many other countries in sub–Saharan Africa, is exposed to natural hazards and disaster events, the most prominent being soil and coastal erosion, flooding, desertification, drought, air pollution as a result of gas flaring, heatwaves, deforestation, and soil degradation due to oil spillage. These events have caused serious disasters across the country. In the southeast region, flooding and gully erosion have led to the displacement of communities. In the Niger Delta region, oil exploration has destroyed the mangrove forests as well as the natural habitat for fishes and other aquatic species and flora. In northern Nigeria, desert encroachment, deforestation, and drought have adversely affected agricultural production, thereby threatening national food security. The federal government, through its agencies, has produced and adopted policies and enacted laws and regulations geared towards containing the disastrous effects of natural hazards on the environment. The federal government collaborates with international organizations, such as the World Bank, International Atomic Energy Agency (IAEA), International Fund for Agricultural Development (IFAD), Center for Infectious Disease Research (CIDR), United Nations Industrial Development Organization (UNIDO), United Nations Environment Programme (UNEP), United Nations High Commission for Refugees UNHCR, and non-governmental organizations (NGOs), to address disaster-related problems induced by natural hazards. However, government efforts have not yielded the desired results due to inter-agency conflicts, corruption, low political will, and lack of manpower capacity for disaster management. There is a need for a good governance system for natural hazards prevention and reduction in the country. This will require inter-agency synergy, increased funding of agencies, capacity building, and public awareness/participation.

Article

American cities developed under relatively quiescent climatic conditions. A gradual rise in average global temperatures during the 19th and 20th centuries had a negligible impact on how urban Americans experienced the weather. Much more significant were the dramatic changes in urban form and social organization that meditated the relationship between routine weather fluctuations and the lives of city dwellers. Overcoming weather-related impediments to profit, comfort, and good health contributed to many aspects of urbanization, including population migration to Sunbelt locations, increased reliance on fossil fuels, and comprehensive re-engineering of urban hydrological systems. Other structural shifts such as sprawling development, intensification of the built environment, socioeconomic segregation, and the tight coupling of infrastructural networks were less directly responsive to weather conditions but nonetheless profoundly affected the magnitude and social distribution of weather-related risks. Although fatalities resulting from extreme meteorological events declined in the 20th century, the scale of urban disruption and property damage increased. In addition, social impacts became more concentrated among poorer Americans, including many people of color, as Hurricane Katrina tragically demonstrated in 2005. Through the 20th century, cities responded to weather hazards through improved forecasting and systematic planning for relief and recovery rather than alterations in metropolitan design. In recent decades, however, growing awareness and concern about climate change impacts have made volatile weather more central to urban planning.