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.
Jason Thistlethwaite and Daniel Henstra
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.
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.
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.
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.
Thomas Thaler, David Shively, Jacob Petersen-Perlman, Lenka Slavikova, and Thomas Hartmann
The frequency and severity of extreme weather events are expected to increase due to climate change. These developments and challenges have focused the attention of policymakers on the question of how to manage natural hazards. The main political discourse revolves around the questions of how we can make our society more resilient for possible future events. A central challenge reflects collective choices, which affect natural hazards governance, risk, and individual and societal vulnerability. In particular, transboundary river basins present difficult and challenging decisions at local, regional, national, and international levels as they involve and engage large numbers of stakeholders. Each of these groups has different perspectives and interests in how to design and organize flood risk management, which often hinder transnational collaborations in terms of upstream–downstream or different riverbed cooperation. Numerous efforts to resolve these conflicts have historically been tried across the world, particularly in relation to institutional cooperation. Consequently, greater engagement of different countries in management of natural hazards risks could decrease international conflicts and increase capacity at regional and local levels to adapt to future hazard events. Better understanding of the issues, perspectives, choices, and potential for conflict, and clear sharing of responsibilities, is crucial for reducing impacts of future events at the transboundary level.
Agent-based models have facilitated greater understanding of flood insurance futures, and will continue to advance this field as modeling technology develops further. As the pressures of climate-change increase and global populations grow, the insurance industry will be required to adapt to a less predictable operating environment. Complicating the future of flood insurance is the role flood insurance plays within a state, as well as how insurers impact the interests of other stakeholders, such as mortgage providers, property developers, and householders. As such, flood insurance is inextricably linked with the politics, economy, and social welfare of a state, and can be considered as part of a complex system of changing environments and diverse stakeholders. Agent-based models are capable of modeling complex systems, and, as such, have utility for flood insurance systems. These models can be considered as a platform in which the actions of autonomous agents, both individuals and collectives, are simulated. Cellular automata are the lowest level of an agent-based model and are discrete and abstract computational systems. These automata, which operate within a local and/or universal environment, can be programmed with characteristics of stakeholders and can act independently or interact collectively. Due to this, agent-based models can capture the complexities of a multi-stakeholder environment displaying diversity of behavior and, concurrently, can cater for the changing flood environment. Agent-based models of flood insurance futures have primarily been developed for predictive purposes, such as understanding the impact of introductions of policy instruments. However, the ways in which these situations have been approached by researchers have varied; some have focused on recreating consumer behavior and psychology, while others have sought to recreate agent interactions within a flood environment. The opportunities for agent-based models are likely to become more pronounced as online data becomes more readily available and artificial intelligence technology supports model development.
Philip Bubeck, Antje Otto, and Juergen Weichselgartner
Floods remain the most devastating natural hazard globally, despite substantial investments in flood prevention and management in recent decades. Fluvial floods, such as the ones in Pakistan in 2010 and Thailand in 2011, can affect entire countries and cause severe economic and human losses. Also, coastal floods can inflict substantial harm owing to their destructive forces in terms of wave and tidal energy. A flood type that received growing attention in recent years is flooding from pluvial events (heavy rainfall). Even though these are locally confined, their sudden onset and unpredictability pose a danger to areas that are generally not at risk from flooding. In the future, it is projected that flood risk will increase in many regions both because of the effects of global warming on the hydrological cycle and the continuing concentration of people and economic assets in risk-prone areas. Floods have a large variety of societal impacts that span across space and time. While some of these impacts are obvious and have been well researched, others are more subtle and less is known about their complex processes and long-term effects. The most immediate and apparent impact of floods is direct damage caused by physical contact between floodwaters and economic assets, cultural heritage, or human beings, with the result for humans being injuries and deaths. Direct flood damage can amount to billions of US dollars for single events, such as the floods in the Danube and Elbe catchment in Central Europe in 2002 and 2013. More indirect economic implications are the losses that occur outside of the flood event in space and time, such as losses due to business disruption. The flood in Thailand in 2011, for instance, resulted in a lack of auto parts supplies and consequently the shutdown of car manufacturing within and outside the flood zone. Floods also have long-term indirect impacts on flood-affected people and communities. Experiencing property damage and losing important personal belongings can have a negative psychological effect on flood victims. Much less is known about this type of flood impact: how long do these impacts last? What makes some people or communities recover faster than others from financial losses and emotional stress? Moreover, flood impacts are not equally distributed across different groups of society. Often, poor, elderly, and marginalized societal groups are particularly vulnerable to the effects of flooding inasmuch as these groups generally have little social, human, and financial coping capacities. In many countries, women regularly bear a disproportionately high burden because of their societal status. Finally, severe floods often provide so-called windows of opportunities, enabling rapid policy change, resulting in new flood risk management policies. Such newly adopted policy arrangements can lead to societal conflicts over issues of interests, equity, and fairness. For instance, flood events often trigger large-scale investment in flood defense infrastructure, which are associated with high construction costs. Although these costs are usually borne by the taxpayer, often only a small proportion of society shares in their benefits. In addition, societal conflict can arise concerning where to build structural measures; what impacts these measures have on the ground regarding economic development potentials, different kinds of uses, and nature protection; and which effects are expected downstream. In such controversies, issues of participation and decision making are central and often highly contested. While floods are usually associated with negative societal impacts in industrialized countries, they also have beneficial impacts on nature and society. In many parts of the world, the livelihood of millions of people depends on the recurring occurrence of flooding. For instance, farming communities in or near floodplains rely upon regular floodwaters that carry nutrients and sediments, enriching the soil and making it fertile for cultivation.
Marta Borowska-Stefańska and Szymon Wiśniewski
Floods, which are among the most dangerous and frequent disasters in the world, are expected to occur more frequently due to climate change. Floods, and flash floods in particular, generate economic, environmental, and social effects. Economic effects include damage to infrastructure, the negative influence upon transportation and communications networks, and an increase in fuel costs, as well as time loss due to traffic delays (congestion) and the necessity of taking alternative routes. It is therefore important to take action both to prevent and to mitigate these effects. In the 21st century there has been a radical change in the approach to the issue of flood protection (as seen in the approach formulated within the 2007 European Floods Directive)—it is no longer believed that there is such a thing as complete protection against floods, but that the damage and loss it inflicts can only be mitigated, and since floods cannot be completely eradicated, societies must learn how to live with them. In the event of a flood, preprepared procedures to counteract and mitigate the effects of the disaster are followed, including the evacuation of people and movable property from affected areas. Evacuation planning is meant to reduce the number of disaster-related (including flood) fatalities and material losses. Crucially, this type of planning requires a well-defined, optimum evacuation policy for people and households within flood hazard areas. In addition, evacuation modelling is particularly important for authorities, planners, and other experts managing the process of evacuation, as it allows for more effective relocation of evacuees to safety. Modelling can also facilitate the identification of bottlenecks within the transportation system prior to the occurrence of a disaster; that is, it enables us to determine the impact of flood-related road closures, and to comprehend—among other things—the effects a phased evacuation has on traffic load. Furthermore, not only may the ability to model alternative evacuation scenarios lead us to establish appropriate policies, evacuation strategies, and contingency plans, but it might also facilitate better communication and information flow. Evacuation from flood-hazard areas is a major challenge for the field of flood risk management as well as the fields of traffic engineering and transport planning. This is particularly true when the research has to include not only those journeys directly related to escape from hazardous places, but also their reflexive relationship with the total number of journeys made in the “background” of the evacuation itself.