Objective of this paper is to study how reliability standards, expressed as probabilities of dike segment failure, can be practically updated to improve opportunities for risk-based dike design and planning. The approach to assess the economic optimal flood probability, used by the Dutch Delta Committee (1958, in this paper referred to as Van Dantzig), is adapted to reflect time-dependent effects of a.o. climate change and subsidence. Furthermore, the approach is adapted to reflect overtopping instead of overflow and it is extended to include reinforcements over time. A comparison of the results of the Adapted Van Dantzig approach with the economic optimal probabilities used as input for the recently formalised Dutch standards (2017) is performed for 73 dike segments in the Netherlands, showing good agreement. Following the Adapted Van Dantzig approach, an analytical relation is developed for economic optimal design horizons, dependent on the dike design, and characteristics of load, investment, climate effect, and economic growth. Finally, a dynamic and simple-to-use approach is developed to enable updating of the economic optimal reliability based on a proposed design and investment planning. This can serve to consider whether an existing reliability standard still fits adequately or needs updating.

Flood defences are often situated in public spaces and are mostly multi-functional, multi-financed and multi-managed. Cooperation in flood defence asset management is important because roles and responsibilities are fragmented within and between organisations. This complex context calls for mutual understanding from responsible role-holders. Research has shown that serious games are instrumental to reflect situations in which technical and social complexity both play a role. Serious games motivate participants to learn and to change the way they learn. This paper presents the development, application, and results of a serious game ‘Dike Dilemmas Under Pressure' that aims to create better mutual understanding between actors in flood defence asset management. The game was played with 67 professionals that fulfil a diversity of roles related to flood defence asset management in the Netherlands. The analysis of the results in this paper clearly shows different preferred cooperative attitudes between different groups of role-holders and indicates potential misperceptions. The game participants were enthusiastic about the insights gained. They indicated that it helped them to recognise the broad variety of asset management dilemmas and become aware of their own cooperative attitudes and those of their colleagues towards dealing with these dilemmas. Future application of the game is recommended to monitor the cooperative attitudes of professionals in flood defence and to support the development of teams.

Flood defences are in practice often multi-used, multi-managed and multi-financed. Flood defence asset management contains technical, organizational and spatial complex issues involving multiple organizations. In the literature, little attention has been given to the conditions for successful cooperation between organizations in flood defence asset management. This paper elaborates on this aspect of mature asset management from a practical point of view. Although the importance of a fit-for-purpose cooperation seems trivial, practice shows that the shape of cooperation is often the coincidental result of implicit or ad-hoc choices and is not deliberately designed. This paper reports on empirical data gathered in a case consisting of five different situations related to collaboration in flood defence management. The management context consists of three main tasks: performance assessment, reinforcement and daily management, and three decision levels: strategic, tactical and operational, resulting in nine different management environments and related interfaces. For effectively achieving desired outcomes, the shape of cooperation has to be explicitly chosen dependent on the complexity of content and organizational context, and relevant external circumstances: situational cooperation.

A system of dikes in flood-prone areas continuously requires measures to mitigate changes such as ageing and climate change. Planning costly measures requires proper insight into system risk effects. Especially in a riverine dike system, the risk contributions of individual assets to the system flood risks are not independent, because reinforcement of a dike upstream increases the risks downstream. Tactical plans define the planning of consecutive measures to implement a flood risk reduction strategy, which may take decades. They may differ due to choices such as a prioritization metric, planning conditions and budget. In this study, a method is developed to compare different tactics to prioritize and plan measures in interdependent systems of dikes to reduce risks most effectively and efficiently. A case study meant as a proof of concept was carried out for the reinforcement of about 500 km of dikes along the Rhine River branches in the Netherlands. We studied the effects of 12 different tactical plans on the aggregated risks over time. The economic risks differ by up to about 40%, and the risks on victims differ by up to 70 %. We conclude that tactical planning and corresponding decisions are important for reduction of time-aggregated flood risks.

Dikes are an effective flood risk reduction measure in deltaic areas. Present risk analyses consist often of decoupled calculations of probabilities of dike failure and calculation of consequences of flooding given dike failure. However, the flood defense design determines not only the probability of failure, but influences the consequences of flooding as well. Especially when the dike has a ductile failure and breach growth behavior, due to a structural robust design, the consequences of flooding reduce. In this article, we present a novel assessment of risks and investments, valuing structural robustness of a construction type, represented by its ductile behavior during high loads. Therefore, the consecutive occurrence of initial dike failure mechanisms, failure path development, breach growth, and consequences is modeled integral and time-dependent. The investments consist of the costs to reinforce or reconstruct the flood defense to behave relatively ductile. This integral assessment enables to compare flood impacts of different construction types and different dimensions of designs. We applied it on a case in a riverine area in the Netherlands. The results show that the total societal costs and the individual risks on victims are very dependent on the construction type. The risk profile of a polder protected by a brittle or a ductile dike differs significantly. The brittle sand dike in the case requires larger dimensions than the more ductile dike with a clay core.

EU Member States invest some €2.5 billion per year in flood protection, yet flood damages continue to increase. A new approach to the planning, design and management of flood protection assets is needed to ensure risks are better managed and asset management is aligned with broader socio-economic policies and supporting governance systems. This paper sets out a policy framework to enable this transition. The framework results from a collaboration of researchers and practitioners from around the North Sea. The findings highlight common challenges and identify four priority Policy Recommendations in response to these: ‘Break free of the silo’ by aligning planning processes; ‘Mind the gap’ between strategic and operational choices; ‘Prepare for change’ by developing multi-functional and flexible plans; and ‘Make space for innovation’ by seeking to manage risk rather than avoiding it.

Uncertainties about climate change consequences, changing societal requirements and system complexity require flood protection asset managers to continuously evaluate their asset management policies and practice to manage risk and improve the resilience of their assets. However, there are many challenges in doing this, with asset operators often facing conflicting interests and major uncertainties about the future needs for asset performance. In the EU Interreg IV FAIR project, flood protection asset owners and operators, with scientific partners from the North Sea Region of Europe collaborated to develop practical guidance for adaptive asset management of flood protection infrastructure. The central component of this guidance is the FAIR framework, presented here. The framework combines insights and principles from ISO 55000 on asset management and ISO 14090 on climate adaptation with asset operator experiences to provide a practical guide for integration of asset management considerations within both strategic and operational contexts via a tactical handshake. This is a means to avoid the common lack of connection between strategic plans and operational practice. The applicability of the framework is illustrated with examples from Pilot Cases within the FAIR project, in which its value in terms of improved asset management and reduced costs has been demonstrated.