Chapter 6 - Confronting complexity in flood risk management

Confronting complexity

Managing flood risks in a changing climate

Towards flood risk reduction: Commonalities and differences between urban flood resilience and risk based on a case study in the Pearl River Delta

Despite traditional measures to prevent disasters, climate change and urbanization increase flood risk. Thus, flood resilience has attracted increased global concern. Understanding the commonalities and differences between flood resilience and risk is arguably important for flood risk reduction. However, these factors have been seldom reported in previous studies, and discussions on the role of flood resilience in flood risk analysis, assessment, and management are lacking. In this study, the association between flood resilience and risk is discussed using a case study in the Pearl River Delta. Flood resilience is quantified using a pressure-state-response (PSR) model, while flood risk is assessed based on the hazard-vulnerability framework and the extension catastrophe progression method. The implications of considering flood resilience in flood risk analysis, assessment, and management are proposed. The results suggest that the overall flood resilience (risk) in the study area is greater (lower) than that in the highly urbanized areas, and areas with low (high) flood resilience (risk) are mainly concentrated within the highly urbanized areas. Indices extracted from human society and highly related to human activities have the same attributes in both frameworks, while indices associated with climate and geography contribute to the two con- cepts differently. Flood resilience supplements the concept of flood risk, and can be incorporated into risk assessment as an index. Moreover, pre-disruption (post-disaster) measures should follow flood risk (resilience) assessment, and strategies that foster flood resilience should be included in flood risk management. This study provides references for flood resilience improvement and risk mitigation.

As the number of COVID19 cases is increasing again in Europe and other areas, the interest in flood risk management is declining. The public and politicians are occupied by more urgent issues, such as health, income, and employment. Especially in countries where the last flood occurred long ago, like the Netherlands, the issue of flood risk management may be moved down on the list of priorities. However, it remains important to continue improving the knowledge on assessing flood risks and developing and evaluating flood risk management strategies. If not, risks may increase, and opportunities for measures may be lost. Climate change will increase flood risks if no counteractions are taken (Haasnoot et al., 2020). Ice sheets are melting faster than anticipated, increasing coastal flood hazards; extreme weather events, and river floods may occur more frequently and become more severe. This may require drastic changes in our flood risk management strategies in the long term. Such changes need time and require debate among scientists, especially policymakers and society. They may also become increasingly difficult by today's decisions, which lock-in our current strategy. Much money is spent on flood risk management, not only after flood events on repair and recovery but also for flood protection. To make sure this money is spent wisely and to prevent regret from having made the wrong decisions, improved flood risk analyses and new approaches to flood risk management are needed. The COVID19 crisis may teach us things about crisis management that may also be useful for flood risk management. Although floods are very different from pandemics, important lessons can be learned, for example, on what is vital and must continue functioning (e.g., schools, health care), on how experts and politicians should or could best work together (sharing responsibilities), on the need of involving all relevant stakeholders when taking decisions, and on communication. The crisis reveals societies' abilities to join forces and take care of each other, as well as their innovative capacities, which results in workable alternatives for shortages in supplies, increased hospital capacity, and adapted procedures that allow opening of buildings and participating in activities in a safer way. These contribute to society's resilience to cope with the pandemic and will also contribute to its recovery in the future. Societal resilience is also crucial in flood risk management. Resilience has been applied to flood risk management for about two decades already (Vis et al., 2003; De Bruijn, 2004). Recently, its popularity has become overwhelming, especially because it has been adopted by three important global post-2015 agendas: The Sustainable Development Goals (SDGs), The Sendai Framework for Disaster Risk Reduction, and the Paris Agreement under the United Nations Framework Convention on Climate Change (IPCC, 2012). Furthermore, resilience is promoted by scientific communities (especially The Resilience Society, but also by the International Conference on Flood Management [ICFM7], who made it the leading concept in 2017) and picked up by many regional and national authorities (e.g., the ADB and EU (ADB, 2014; EU, 2013), the 100 Resilience City programme of the Rockefeller foundation (ARUP, 2014), and the Netherlands' Delta Program (MOIE, 2015). There is thus a broadly shared vision that enhancing resilience is needed. However, there is no common understanding on what precisely implies enhancing resilience. Resilience has been defined in different ways, varying from very narrow as “the ability to recover from a response to disturbance such as a flooding” to very broad as: “the ability to cope with disturbances and changes by avoiding or minimizing impacts and having the ability to learn and adapt in order to remain resilient into the future”. Lately, it appears to have become an umbrella concept, covering almost everything that was previously covered by “sustainability” and including adaptation (adaptive management) and transformation (DHS, 2008). Although the resilience concept has been used in many ways, this does not mean it is only a buzzword. As the popularity of the word already shows it covers something that was felt to be missing before. In flood risk management, decisions are often based on risk analysis. These risk analyses could, in theory, include potential impacts that are relevant to society. However, they are often simplified and focused on direct impacts corresponding with maximum flood depths with a certain probability of exceedance. Sometimes, business interruption of flooded companies and fatality risk are also included, but all other indirect and non-monetary impacts are generally excluded. As the analyses focus on maximum water depths only and not on the whole chain of events leading to those water depths, measures which do not directly affect that water depth cannot be easily considered. Specifically, measures aiming to increase warning time, improve effective emergency response, enhance recovery, or build differently or, elsewhere, reduce future risk increase are often not considered. Such a limited application of risk analysis may lead to suboptimal choices of measures. Moreover, science favours presenting integrated risk numbers, whereas laypeople do not perceive risk from small-probability catastrophes as similar to risk linked to frequent small-impact events. The very extreme events may seem irrelevant for the total risk, but they may be considered relevant by decision-makers if their potential effects would be shown to them. Although the insurance industry considers the entire flood loss curve, most flood risk analyses give only a single risk number. This number does not reveal deep uncertainties and potential surprises that may occur and their effects (Merz et al., 2015). Finally, flood risk management is still often the responsibility of water authorities, while a more comprehensive and tailored approach towards society would require the engagement of citizens, industries, critical infrastructure operators, and local governments. They are the ones that should benefit from improved flood risk management and, therefore, should be engaged, and they could contribute, although they may not have the full picture. As learned from the COVID19 crisis, to cope with a hazard, engagement of all actors is needed. Adopting resilience means being willing to address more aspects than usually addressed in flood risk analyses and developing comprehensive strategies that enable societies to cope with hazards of all magnitudes. Resilience analysis involves analysing the response of systems to extreme events (e.g., of cities, countries or societies, also including flood management infrastructure such as embankments or barriers), a response that cannot be expressed “only” by euros per year but should reveal the response to both frequent and very rare events, the effect on economy, well-being, and all that matters to society during the event, not only in its aftermath and during recovery but also in the long term. Furthermore, adopting resilience as a guiding principle for the design of future strategies may lead to a different starting point: The hazardous events are not considered central but the society and its most important characteristics and developments. What putting resilience into the practice of flood risk management means is still to be decisively established. Research on this is intensifying but still struggles making things practical. The adoption of a number of guiding principles may be of help in this regard (De Bruijn et al., 2017). Principles such as “applying a systems approach” (vs. local optimization) (Vorogushyn et al., 2018), “also consider beyond-design events and how to cope with such events”, “assess what must remain functioning” instead of only what damage is expected, “assess the recovery capacity” of a society, and identify trends and developments that may affect or offer opportunities to strengthen “future resilience” are mentioned. To really put these into practice, better indicators, examples, tools methods, and evaluation criteria are needed. Equity (in space, between groups, and between generations) may, next to cost–benefit ratios and effects on nature, be included more often, as covered by the term inclusive green growth. A focus on resilience thus changes our mindset from quantification of risk to understanding system behaviour and societal needs under a full range of possible events and prolonged time scales. This requires elaborating existing approaches and developing new approaches aimed at enabling societies to cope with flood hazards now and in the future.

The construction of flooding and flood risk management are complex and there is potential for dissonance between individual and institutional understanding and experience of both. In this article, we start by investigating how flooding is managed and the change in paradigm from flood defence to more adaptive approaches, which embed resilience into flood risk management. Using analysis of semi‐structured interviews with members of the flood authorities in England, we explore how flood management authorities construct ‘flooding’ and establish that it is often defined by in‐the‐moment impacts. Whilst these in‐the‐moment impacts are understood to be devastating, there is less appreciation of long‐term human impacts of living at risk of flooding. We uncover how the construction of ‘flood risk management’ by the flood authorities is complicated by factors, such as the construction of resilience, availability of funding, technical expertise and responsibility fragmentation that the Floods and Water Management Act (2010) has created. We conclude that the differing constructions of flooding and flood risk management between flood management authorities in England hinder how flooding is managed. Therefore, we propose that a more nuanced understanding of flooding and flood risk management is essential for effective partnership working between flood risk management authorities and communities.

Abstract. This article presents a methodology for estimating flood risk in urban areas integrating pluvial flooding, river flooding and failure of both small and large dams. The first part includes a review of basic concepts on flood risk analysis, evaluation and management. Flood risk analyses may be developed at local, regional and national level, however a general methodology to perform a quantitative flood risk analysis including different flood hazards is still required. The second part describes the proposed methodology, which presents an integrated approach – combining pluvial, river flooding and flooding from dam failure, as applied to a case study: an urban area located downstream of a dam under construction. The methodology enhances the approach developed within the SUFRI project ("Sustainable Strategies of Urban Flood Risk Management to cope with the residual risk", 2009–2011). This article also shows how outcomes from flood risk analysis provide better and more complete information to inform authorities, local entities and the stakeholders involved in decision-making with regard to flood risk management.

Flood risk analysis for metropolitan areas – a case study for Shanghai

Flood resilience is increasingly discussed in academia and practice as a complement to existing flood risk management approaches (Fekete, Hartmann, & Jüpner 2020). It is seen as a promising concept to deal with increasingly severe consequences of climate change in general, and with increasing flood risk in particular. The debate on flood resilience is linked to the paradigm shift from flood protection to risk management, which started in Europe after the major river flood events in 1993 and 1995 along the river Rhine (Hartmann, 2012), and has developed over the past decades—pushed by further major fluvial and pluvial flood events (Begum, Stive, & Hall, 2007; Hartmann & Juepner, 2014; Klijn, Samuels, & van Os, 2008; Patt & Jüpner, 2020). However, in flood risk management, the academic debate on resilience is only in its infancy (Jüpner et al., 2018; Vis, Klijn, Bruijn, & Buuren, 2003). Many different definitions exist (Disse, Johnson, Leandro, & Hartmann, 2020). Especially when it comes to specific implementation of resilience, the vagueness of the concept—which is sometimes described as one of its strengths (Baggio, Brown, & Hellebrandt, 2015; Brand & Jax, 2007)—can present a problem. How to design a resilient hydraulic infrastructure? This question has not only technical but also concerned with financial and legal aspects. This becomes more complicated when individual protection measures are put in a context of a larger system, such as a city or a region. When and how is a system such as a city or a region resilient, and how does one measure resilience? These questions are important, not only for construction but also for legal (such as liabilities), financial (budgetary), and political reasons. In other words, resilience is not (yet) a ready-to-use concept in flood risk management. Resilience challenges presumptions of traditional flood risk management in many ways. Resilience implies that more and different stakeholders and actors will be involved in flood risk management than before, such as landowners or spatial planners. Hitherto, flood risk management has been and still is mainly the domain of water management (Hartmann & Driessen, 2017), although the prevalence of the traditional civil engineering approach has been questioned before (van den Brink, 2009). This change is not positive for all actors—affected homeowners, but also city planners or mayors now must deal with questions that were previously outside of their realm of competence and responsibility. From a flood risk management perspective, many questions arise, such as: How does resilience add to and change the existing flood risk management system? How can resilience contribute to a more effective and efficient flood risk management approach? What are the specific advantages of integrating resilience in flood risk management? How can resilience be measured and quantified? Which parameters are most relevant? This special collection brings together contributions from different disciplines that address the specific challenges of implementing resilience in flood risk management. The special collection takes the European debate as a starting point. The European Floods Directive from 2007 (2007/EC/60) pushed the debate on flood risk management and resilience in Europe. This Directive established a legal frame on how countries in the European Union have to deal with flood risk for the first time (Hartmann & Jüpner, 2014). At the same time, the shift toward a risk-based approach raised questions such as "what can happen?" "what must not happen?" and "which security level can be realized at which costs?" Ultimately, flood risk management replaces the paradigm of complete protection against floods with the idea of managing the risk (Grünewald, 2005). This makes approaches to resilience and the reduction of damage potential (vulnerabilities)—not only for river floods but also for pluvial rainfall—important. The first three papers in this collection highlight the necessity and consequences of defining the concept of resilience. In their opinion paper, Fekete, Hartmann, and Jüpner (2020) point out that resilience is indeed a trend that neither can nor should be ignored in flood risk management, rather than it should be embraced—with a caveat: the concept is still not exactly defined and cannot be understood as a panacea for all shortcomings and challenges of flood risk management. So, is resilience merely a new buzzword? Dewulf et al. (2019) discuss the power and impact of defining resilience and therewith unravel the political-normative notion of flood resilience as a concept. This illustrates that, with flood resilience, flood risk management turns much more strongly towards social and political science than ever before. Discussing resilience and its definition is thus a crucial step toward successfully implementing it in flood risk management. In her advanced review, Rodina (2019) reveals different notions of resilience in different disciplines when taking on a broader view of the concept (i.e., not solely focusing on flood risks). She concludes that participation and stakeholder involvement are important components of resilience—a theme that is picked up in the next section of this special collection as well. So, though this article had not been part of the original set-up of the special collection, the conclusions are highly relevant for implementing flood resilience in flood risk management. Resilience requires more action by homeowners and citizens. All papers in this section of this special collection leave no doubt about that. Snel, Witte, Hartmann, and Geertman (2020), however, start with a very critical point of departure, namely that many publications on homeowner and citizen involvement do not seem to question if this involvement is necessary. The paper unravels the arguments that are prevalent in the academic debate for more involvement of homeowners in flood resilience, which supposedly comes along with a shift towards flood governance. Four types of main arguments are identified and discussed in the paper. Kuhlicke and the multidisciplinary team of authors writing on the behavioral turn in flood risk management (Kuhlicke et al., 2020) discuss in detail three underlying assumptions of increased involvement of citizens in flood risk management: the motivations of citizens, the effectiveness of measures, and capacities of citizens. In this vein, Rufat et al. (2020) discuss in their opinion paper need for a more nuanced debate on the link between flood risk perception and risk-mitigating behavior. Attems, Thaler, Genovese, and Fuchs (2020) then provide an overview of the measures that homeowners can take to enhance resilience by using property-level flood risk adaptation (PLFRA) measures. The paper confirms that such measures can indeed be an appropriate addition or complement to flood risk management. The third group of papers in this special collection addresses the issue of measuring and communicating resilience. The need for this comes not only from hydraulic engineering but also from the need to communicate about flood risk with homeowners and citizens, as they have to become more involved (as the earlier papers in this special collection clearly show). Pohl (2020) views resilience from a hydrological as well as a hydraulic engineering perspective and outlines what it means to include the concept in flood risk management. In particular, the contribution points out the difficulties of embedding resilience as a design criterion in hydraulic structures. Pohl concludes that—though the fuzziness of resilience is appreciated by some social scientists as a "boundary concept" (Baggio et al., 2015)—hydraulic engineering and hydrology inevitably require some quantifiable measurement of resilience. Fekete (2019) elaborates in his paper how cascading effects and critical infrastructure matter for flood resilience. It thereby shows how flood resilience with this perspective extends existing flood risk management approaches. Cascading effects of critical infrastructure can substantially affect the measurement of flood resilience. Schmitt and Scheid (2020) discuss the need for better risk communication and discuss approaches by focusing on pluvial floods. In particular, they show how a rainstorm severity index may supersede the communicative capacity of statistical rainfall parameters in the communication with nonexperts especially. In conclusion, the contributions in this special collection show how the concept of resilience is advancing flood risk management but also point out some crucial changes and challenges that flood resilience as a concept brings to the practical implementation of flood risk management. It seems inevitable that homeowners especially will play a much more fundamental role in flood resilience, which raises needs for measuring and communication of flood resilience. Along with this shift in flood risk management, the papers illustrate that flood resilience puts flood risk management in a hitherto unknown domain for many water managers, as flood resilience means embracing social and political science. Embedding flood resilience into flood risk management becomes a balancing act—on the one hand, resilience is a political and normative concept, but on the other hand, it needs to be implemented with concrete steps designed via civil engineering and hydrology. This tension is still unsolved and remains a dilemma in implementing flood resilience.

Preface. Acknowledgement. Part 1. Flood risk management. Flood risk management - a basic framework J. Schanze.- Part 2. Flood hazard modelling. A European perspective on current challenges in the analysis of inland floods risks P.G. Samuels.- Hydro-informatics' tool in practice ,,before - during - after' August 2002 flood on Vltava and Elbe catchments - Czech Republic J. Spatka et al. Experiences in application of HEC-RAS model under circumstances of flood waves S. Kovacs et al. Study of possible flooding in the chemical factory as a basis for flood management plan improvement M. Luka et al. Flood risk mapping and mitigation in central Italy S. Pagliara. On the choice of spatial interpolation method for the estimation of 1- to 5-day basin average design precipitation S.Kohnova et al. Regional climate change - To be included in future flood risk analysis? Chr. Bernhofer et al.- Part 3 Flood forecasting. Application of EO data on flood forecasting for the Crisuri basin, Romania G. Stancalie et al. Flood forecasting in the Crisul Alb and Crisul Negru basins using GIS data base R.P. Mic et al. Flood monitoring using on-line support system for spatial information management V. Craciunescu et al. Flood forecasting concept for Turkey: Technical and organisational aspects Th. Einfalt.- Part 4. Vulnerability and flood damages. Flood damage, vulnerability and risk perception Challenges for flood damage research F. Messner and V. Meyer. Flood risk assessment in the Netherlands with focus on the expected damages and loss of life A. Roos and B. Jonkman.- Part 5. Mitigation measures. Flood Protection in the Tisza River basin Z. Balint and S.Toth. Management strategies for flash floods in Saxony, Germany E. Precht et al. Red River flooding - mitigation planning in an international river basin D. LeMarquand. Overview of US National Flood Insurance Program B. Juza. Strategies for flood risk management A processperpective G. Hutter.- Part 6. Historical floods and transboundary issues. Historical and recent floods in the Czech Republic: Causes, seasonality, trends and impacts R. Brasdil et al. Historical 2002 flood in central Europe and flood defence recent floods in the Czech Republic: Causes, seasonality, trends and impacts V. Jirasek. The flood in August 2002 - Consequences of flood protection for the City of Dresden Chr.Korndorfer. Flood risk in cities of Belarus: Specific cases and problems of management T.I. Kukharchyk. NATO Science for Peace Project on management of transboundary floods in the Crisul-Koros River system J. Marsalek. April 2002 flood in the Crisul Aib River basin Transnational co-operation Rom-Hun for flood mitigation O. Streng et al.- Part 7. Conclusions. Conclusion of the Advanced Research Workshop J. Schanze et al.- List of participants. Index.

Floods cause distress and damage wherever and whenever they happen. Flooding from rivers, estuaries and the sea threatens many millions of people worldwide and economic and insurance losses from flooding have increased significantly since 1990. Across the European Union, flood management policy is changing in response to the EU Directive on the assessment and management of flood risks, which requires a move from flood protection and defence to comprehensive flood risk management. Flood Risk Management: Research and Practice includes about 200 contributions from the international conference FLOODrisk 2008 (Oxford, UK, 30 September – 2 October 2008). FLOODrisk 2008 was an initiative of the FLOODsite research project on Integrated Flood Risk Analysis and Management Methodologies. FLOODsite was a major “Integrated Project” in the European Commission Sixth Framework Programme; contract number GOCE-CT-2004-505420. The conference provided a forum for leading researchers, flood risk managers, policy makers and practitioners from government, commercial and research organisations to gain an overview of advances in this important subject. Flood risk management practice crosses several professions and disciplines and these are represented in the breadth of the scope of the conference and these proceedings. The conference covered all aspects of flood risk: the causes of floods, their impacts on people, property and the environment, and portfolios of risk management measuresm, while the principal themes included: climate change, estimation of extremes, flash floods, flood forecasting and warning, inundation modelling, systems analysis, uncertainty, international programmes, flood defence infrastructure and assets, environmental impacts, human and social impacts, vulnerability and resilience, risk sharing, equity and social justice, and, civil contingency planning and emergency management. Flood Risk Management: Research and Practice will be of interest to an international readership, ranging from authorities, consultants and engineers involved in flood management; researchers, post graduate lecturers and students, to policy makers, particularly at national level.

On 27 June 2006 the Council of the European Union reached political agreement on a draft directive on the assessment and management of flood risks. This directive prescribes approaches and procedures which should be met by the member states. The website of the EU on this directive links to another EU‐initiative, the Integrated Project FLOODsite, which aims at providing methodologies for flood risk analysis and management. Obviously, the directive and the IP emerged in a common but much larger context of public and scientific debate on a more integrated and coordinated approach to dealing with flood risks. In this paper we briefly discuss this context and examine a few national cases in order to find out whether flood risk management is already common practice or is still in its infancy, or whether it involves merely good intentions. We base this examination primarily on our experiences within FLOODsite and on presentations held within the special session on River Flood Risk Management which was organised by The Netherlands Centre for River Studies (NCR) during the ISDF3 conference in May 2005. This paper goes into the similarities and differences between some national approaches and tries to place them in a cultural context. It appears that the seemingly most sophisticated management policies do not automatically imply the most comprehensive flood risk management approach. But the intention to evolve from flood management into flood risk management is evident and promising.

Several modeling tools commonly used for supporting flood risk assessment and management are highly effective in representing physical phenomena, but provide a rather limited understanding of the multiple implications that flood risk and flood risk reduction measures have on highly complex systems such as urban areas. In fact, most of the available modeling tools do not fully account for this complexity—and related uncertainty—which heavily affects the interconnections between urban systems evolution and flood risk, ultimately resulting in an ineffective flood risk management. The present research proposes an innovative methodological framework to support decision‐makers involved in an urban regeneration process at a planning/strategic level, accounting for the multi‐dimensional implications of flood risk and of different flood risk management strategies. The adopted approach is based on the use of System Thinking principles and participatory System Dynamics modeling techniques, and pursues an integration between scientific and stakeholder knowledge. Reference is made to one of the case studies of the CUSSH and CAMELLIA projects, namely Thamesmead (London), a formerly inhospitable marshland currently undergoing a process of urban regeneration, and perceived as being increasingly vulnerable to flooding. It represents an interesting opportunity for building a replicable modeling approach to integrate urban development dynamics with flood risk, ultimately supporting policy and decision‐makers in identifying mitigation/prevention measures and understanding how they could help achieve multi‐dimensional benefits (e.g., environmental, social and economic).

Large-scale flood risk assessment and management: Prospects of a systems approach

Flood risk management has become more significant in the face of rapid urban development and the climate change. Many governments and the decision makers have recognized the requirement of resilient flood management policies and strategies for sustainable urban development. During the recent decades, various conceptual framework of flood risk assessment and management emerged and they in turn questioned the characterization of resilience in flood risk management. More recently, research on flood risk management and spatial planning have demonstrated a common discussion platform appreciating the concept of flood resilience in policy and strategy making. However, assessment and operationalization of flood resilience is often questionable due to its conceptual vagueness. The present work is a review of the plurality views of flood resilience. Resilience thinking has moved the focus of flood risk assessment towards vulnerability. Flood resilience embeds the incorporation of spatially distributed land use policies and regulations which are a must for the management of flood vulnerability. Spatial planning reflecting flood resilience becomes vital when managing the uncertainty incorporated with flood risk management. However, the operationalization and legitimacy of the importance of the combined role of spatial planning and flood risk management with stakeholder acceptance still remains implicit and weak.