The policy programme Integrated River Management (IRM) aims to anticipate climate change and to redress the negative consequences of earlier river engineering interventions. Its objective is to first and foremost ensure a well-functioning river system that can provide its essential ‘public’ geo-ecosystem services: safe discharge of floods, reliable freshwater supply, reliable waterways to the hinterland, and good conditions for aquatic and terrestrial ecosystems in the floodplains and beyond. Challenges, however, relate to the changing discharge regime resulting from climate change, and to the conflicting requirements of the various river functions and values. These pose real dilemmas about when to act, how to act, which function or value to support and which one to curb.@en

Robust Decision Making (RDM) is an established framework for decision making under deep uncertainty. RDM relies on the idea of scenario neutrality, namely that decision robustness is not affected by how scenarios are generated if these are uniformly distributed and span a sufficiently large range of future states of the world. Several authors have shown that scenario neutrality may not hold, but they did so by adopting either new or computationally expensive modeling. We introduce the Belief-Informed Robust Decision Making (BIRDM) framework to assess how robustness might change under an arbitrary large number of non-uniform distributions at virtually no additional costs with respect to RDM. We apply BIRDM to a flood management problem and find that alternative distributions change the robustness and ranking of measures. BIRDM allows identifying what distributions lead to these changes and under what set of distributions a measure has a specific robustness and rank.@en

To support equitable adaptation planning, quantitative assessments should consider the fairness of the distribution of outcomes to different people. What constitutes a fair distribution, however, is a normative question. In this study, we explore the use of different moral principles drawn from theories of distributive justice to evaluate fairness. We use adaptation planning in Vietnam Mekong Delta as a case study. We evaluate the preference ranking of six alternative policies for seven moral principles across an ensemble of scenarios. Under the baseline scenario, each principle yields distinctive preference rankings, though most principles identify the same policy as the most preferred one. Across the ensemble of scenarios, the commonly used utilitarian principle yields the most stable ranking, while rankings from other principles are more sensitive to uncertainty. The sufficientarian and the envy-free principles yield the most distinctive ranking of policies, with a median ranking correlation of only 0.07 across all scenarios. Finally, we identify scenarios under which using these two principles results in reversed policy preference rankings. Our study highlights the importance of considering multiple moral principles in evaluating the fairness of adaptation policies, as this would reduce the possibility of maladaptation.@en

Climate change and socio-economic development result in increasing flood risk which challenges flood risk management policy making and practice. Each situation, however, is different and calls for not only understanding the natural context, but also the socio-economic and cultural context. Only then Flood Risk Management strategies can be designed that are not only 1) fit for purpose but also 2) feasible for local implementation and 3) sustainable into the future. Flood consequences that are accepted in some cultures (fatalist), may not be acceptable in other cultures (controlist). This calls for considering the local normative context in order to understand current differences in policy and practice. More importantly, the design of strategic alternatives for Flood Risk Management into the future should consider this socio-economic and cultural context as well because not every society aims for the same goals in the same proportion, nor is equally willing or capable to implement and maintain sophisticated infrastructure and dedicated institutions. Based on literature on cultural theory and national cultures, we hypothesized that acknowledging socio-economic and cultural differences would allow to better appreciate the rationale of current flood risk management policies and practices in different parts of the world. By analysing cases related to Deltares projects abroad, we explored whether these factors explain the main differences observed. Based on this preliminary exploration, we propose a shortlist of factors to consider when designing future flood risk management strategies tailored to local socio-economic and cultural contexts.

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The need for explicitly considering equity in climate change adaptation planning is increasingly being recognized. However, evaluations of adaptation often adopt an aggregated perspective, while disaggregation of results is important to learn about who benefits when and where. A typical example is adaptation of rice agriculture in the Vietnam Mekong Delta (VMD). Efforts focused on flood protection have mainly benefitted large-scale farmers while harming small-scale farmers. To investigate the distributional consequences of adaptation policies in the VMD, we assess both aggregate total output and equity indicators, as well as disaggregated impacts in terms of district-level farming profitability. Doing so requires an adequate representation of the multisectoral dynamics between the human and biophysical systems which influence farming profitability. We develop a spatially explicit integrated assessment model that couples inundation, sedimentation, soil fertility and nutrient dynamics, and behavioral land-use change and farming profitability calculation. We find that inter-district inequality responds in a non-linear way to climatic and socio-economic changes and choices of adaptation policies. The patterns of who wins and who loses could change substantially when a different policy is implemented or if a slightly different uncertain future materializes. We also find that there is no simple ranking of alternative adaptation policies, so one should make trade-offs based on agreed preferences. Accounting for equity implies exploring the distribution of outcomes over different groups over a range of uncertain futures. Only by accounting for multisectoral dynamics can planners anticipate the equity consequences of adaptation and prepare additional measures to aid the worse-off actors.

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Flood risk management decisions in many countries are based on decision-support frameworks which rely on cost-benefit analyses. Such frameworks are seldom informative about the geographical distribution of risk, raising questions on the fairness of the proposed policies. In the present work, we propose a new decision criterion that accounts for the distribution of risk reduction and apply it to support flood risk management decisions on a transboundary stretch of the Rhine River. Three types of interventions are considered: embankment heightening, making Room for the River, and changing the discharge distribution of the river branches. The analysis involves solving a flood risk management problem according to four alternative formulations, based on different ethical principles. Formulations based on cost optimization lead to very poor performances in some areas for the sake of reducing the overall aggregated costs. Formulations that also include equity criteria have different results depending on how these are defined. When risk reduction is distributed equally, very poor economic performance is achieved. When risk is distributed equally, results are in line with formulations based on cost optimization, while a fairer risk distribution is achieved. Risk reduction measures also differ, with the cost optimization approach strongly favoring the leverage of changing the discharge distribution and the alternative formulations spending more on embankment heightening and Room for the River, to rebalance inequalities in risk levels. The proposed method advances risk-based decision-making by allowing to consider risk distribution aspects and their impacts on the choice of risk reduction measures.

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Door klimaatverandering verandert het afvoerregime van onze grote rivieren. Hoogwaters worden hoger en frequenter, laagwaters lager en langduriger. Hoe we daarop reageren hangt af van hoe we klimaatverandering zien: als opgave, of als kans om onvolkomenheden aan te pakken. In dit artikel presenteren we aanzetten voor een meer geo-ecologisch gefundeerde inrichting, of – naar McHarg – voor design with nature. Climate change is expected to significantly influence the discharge regime of the Rhine and Meuse rivers. Floods may increase in magnitude and occur more frequently; low discharges are likely to become even smaller and last longer. How to respond to those changes? Can all river functions be fulfilled into the future and which interventions are then needed to keep the country safe and the rivers navigable? The answer to these questions depends on whether climate change is primarily considered as a challenge, or rather as an opportunity to, at the same time, redress a few deficiencies and detrimental geo-ecological developments that are being provoked by how we straightjacketed our floodplains and engineered our rivers in behalf of navigation but negatively impact biodiversity. We propose a more geo-ecologically grounded approach to our rivers’ spatial design and management – inspired by McHarg’s design with nature –, which encompasses making available much more room for safe flood discharge and reduced hydrodynamics for ecosystem development in the floodplains, as well as more nature-based river training to allow for morphological developments and natural rejuvenation. @en

Most alluvial plains in the world are protected by flood defences, for example, embankments, whose primary aim is to reduce the probability of flooding of the protected areas. At the same time, however, the presence of embankments at one area influences hydraulic conditions of downstream areas located on the same river. These hydraulic interactions are often neglected in current flood risk management. The aim of this study is to explicitly acknowledge hydraulic interactions and investigate their impact on establishing optimal embankment heights along a stretch of the IJssel River. We find that the current approach leads to a single solution, while taking into account hydraulic interactions substantially expands the number of promising solutions. Furthermore, under a reference scenario, the current approach is in fact suboptimal with respect to both downstream locations and the system as a whole. Under uncertainty, it performs adequately from a system viewpoint, but poorly for individual locations, mostly due to risk overestimation downstream. Overall, the current approach proves to be too short-sighted, because spatial trade-offs among locations are neglected and alternative solutions remain hidden. Acknowledging the effect of hydraulic interactions provides policy makers with a broader and more comprehensive spectrum of flood risk management strategies.

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Rivers typically flow through multiple flood-protected areas which are clearly interconnected, as risk reduction measures taken at one area, e.g. heightening dikes or building flood storage areas, affect risk elsewhere. We call these interconnections 'hydraulic interactions'. The current approach to flood risk management, however, neglects hydraulic interactions for two reasons: They are uncertain and, furthermore, considering them would require the design of policies not only striving for risk reduction, but also accounting for risk transfers across flood-protected areas. In the present paper, we compare the performance of policies identified according to the current approach with those of two alternative formulations: One acknowledging hydraulic interactions and the other also including an additional decision criterion to account for equity in risk distribution across flood-protected areas. Optimal policies are first identified under deterministic hydraulic interactions, and, next, they are stress-tested under uncertainty. We found that the current approach leads to a false sense of equal risk distribution. It does, however, perform efficiently when a risk-averse approach towards uncertain hydraulic interactions is taken. Accounting for hydraulic interactions in the design of policies, instead, increases efficiency and both efficiency and equity when hydraulic interactions are considered deterministically and as uncertain, respectively.

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Over decades the concept of integration has been promoted to enhance alignment between policy domains, and to manage trade-offs and maximize synergies across management practices. Integrated approaches have the potential to enable better outcomes for flood risk management (FRM) and society as a whole. However, achieving integration in practice is a recurring challenge, especially for FRM where multiple actors need to work together across fragmented policy domains. To disentangle this complexity of integration, a framework is proposed for assessing integration and identifying different degrees of integration. This framework is based on evidence from a literature review, 50 interviews with FRM-related professionals in England, and participant observation at 24 meetings relevant for FRM. The framework sets out the context of integration, assesses the governance capacity for integration through the strength of relationships between different types of actors (bridging, bonding, and linking) and the mechanisms (actor-, rule-and resource-based) that influence them, and the realization of integration in practice through knowledge, policies, and interventions. The framework is applied for FRM in England and used to identify degrees of integration: high, intermediate, low, and minimal. An important characteristic of the framework is the interconnectivity between the governance capacity and realization of integration. The framework provides further theoretical insights into the concept of integration, while offering an approach for researchers, policy makers, and practitioners to recognize current degrees of integration in FRM and identify the critical elements for improvement. It is recommended that further research and practice-based applications of the framework are completed in different geographical and institutional contexts. Specifically, such applications can create further understanding of the interactions and dependencies between elements of the governance capacity and realization of integration.

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The Netherlands has just finished implementing the Room for the Rivers program along the Rhine and Meuse Rivers in response to increasing river discharges. Recently, making more room for the river is, however, being challenged for future application because the flood defenses are assessed to be too weak and will need reinforcement anyway. To be able to decide on the most desirable policy for the remainder of the century, we require knowledge of all benefits and costs of individual interventions and strategic alternatives for flood mitigation. In this paper, we quantify some benefits of making more room for the rivers. We recognize and quantify two risk-reducing effects and provide results of analyses for the Rhine and Meuse Rivers in The Netherlands. Making room for rivers was originally advocated because it (1) reduces the consequences of flooding, as well as (2) reduces the probability of failure of the embankments. We have now quantified these effects allowing translation into risk reduction proper. Moreover, larger floodplain surface area may influence the relationship between discharge and flood level, which implies that rivers with widened floodplains are less sensitive to uncertainties about future river discharges. This does not reduce risk proper, but makes the river system more robust, as we shall argue in the discussion where we present risk reduction and robustness as complementary perspectives for assessing strategic alternatives for flood risk management@en

There is increasing attention for the robustness of systems, in view of more frequent and more extreme weather events. Calls to increase a system's robustness are usually motivated by the resulting reduced sensitivity to extreme events and uncertainties about their probability of occurrence. The concept has been elaborated for flood risk systems, but recently questions have arisen about whether subsystems, such as flood defences or rivers, should and could also be assessed on their robustness. Against the background of a recent debate in the Netherlands about whether to raise the embankments again or to make more room for the rivers in anticipation of increasing extreme river discharges into the future, we propose to define the robustness of embanked alluvial rivers by their sensitivity to uncertainties in flood discharge, expressed by the relationship between discharge and flood water level. We assess the Rhine River branches and Meuse River in the Netherlands and show how their planform, as defined by the location of the embankments and the presence of obstacles in the floodplains, causes remarkable differences in robustness per river and per river stretch. We finally discuss what this might entail for policy planning.@en

The concept of resilience is used by many in different ways: as a scientific concept, as a guiding principle, as inspirational ‘buzzword’, or as a means to become more sustainable. Next to the academic debate on meaning and notions of resilience, the concept has been widely adopted and interpreted in policy contexts, particularly related to climate change and extreme weather events. In addition to having a positive connotation, resilience may cover aspects that are missed in common disaster risk management approaches. Although the precise definition of resilience may remain subject of discussion, the views on what is important to consider in the management of extreme weather events do not differ significantly. Therefore, this paper identifies the key implications of resilience thinking for the management of extreme weather events and translates these into five practical principles for policy making.

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Knowledge on the different components of flood risk has much improved over the last decades, but research which fully takes into account not only the interactions between those components but also between different areas in a catchment or delta is still rare. Integrated analyses based on a complete system's approach at sufficiently large scale will improve our understanding of how flood risk systems with flood protection infrastructure in place behave under extreme conditions, it may help to develop sensible long-term strategies, and allows us to better prepare for flood events of all magnitudes. To illustrate the relevance of a hydrodynamic system's approach for flood risk management we analyse the effect of defence breaches on flood risks elsewhere along the lower Rhine River and discuss the use of this knowledge for flood risk management.

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The Netherlands is updating its flood protection, whilst fully taking into account climate change and socioeconomic development. This translates in 'anticipatory standards' which need to be met in 2050, and which apply for the then foreseen climate and economy. Whilst the government maintains to have adopted a policy of adaptive planning and management, the new standards are thus based on one future situation, which qualifies as a 'high end scenario' from a flood risk management perspective. The consequences of adopting these new standards are now becoming clear. It is expected that many hundreds of kilometres of primary flood defences need to be reinforced and/or raised, at an estimated investment of about 9-14 billion euros. The many uncertainties about actual future development, however, complicate the decision making about the implementation of individual reinforcement projects: should one aim at immediately meeting the new standard or gradually improve and grow towards it? In this paper we discuss the uncertain decision making context, show that lawfulness (working according to procedures, rules and regulations) and expediency (towards a purpose) may jeopardize the good intentions of adaptive management, and argue that optimization may not provide the most useful answer to this decision making problem.

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Since 1996, the Netherlands has adopted a flood risk management policy based on making more room for the rivers. Currently, the focus in flood risk management is being adapted again, in view of increasing societal vulnerability and foreseeable effects of climate change. In this context, the choice between making more room for the river and/or strengthening embankments is again of major concern. This calls for further quantification of the effectiveness, costs and benefits of all possible measures. Making room for rivers was originally advocated by referring to a reduction of the probability of failure of the embankments and a reduction of the consequences in case of breaching. These arguments still apply, but the effect of making more room for rivers on flood risk has never been properly quantified yet. In this paper we identify three potential risk reducing effects, and quantify their effect for along the Rhine and Meuse Rivers in the Netherlands. We show that lowering the flood levels means smaller flood probabilities, that larger floodplain surface area significantly influences the relationship between discharge and flood level, and that lower flood levels in the river translate into smaller flooding depths and/or flood extent, and thus reduce the consequences of flooding.

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