While adapting to future sea-level rise (SLR) and its hazards and impacts is a multidisciplinary challenge, the interaction of scientists across different research fields, and with practitioners, is limited. To stimulate collaboration and develop a common research agenda, a workshop held in June 2024 gathered 22 scientists and policymakers working in the Netherlands. Participants discussed the interacting uncertainties across three different research fields: sea-level projections, hazards and impacts, and adaptation. Here, we present our view on the most important uncertainties within each field and the feasibility of managing and reducing those uncertainties. We find that enhanced collaboration is urgently needed to prioritize uncertainty reductions, manage expectations and increase the relevance of science to adaptation planning. Furthermore, we argue that in the coming decades, significant uncertainties will remain or newly arise in each research field and that rapidly accelerating SLR will remain a possibility. Therefore, we recommend investigating the extent to which early warning systems can help policymakers as a tool to make timely decisions under remaining uncertainties, in both the Netherlands and other coastal areas. Crucially, this will require viewing SLR, its hazards and impacts, and adaptation as a whole.

Flood defence systems can be seen as multiple interdependent flood defences. This paper advances an approach for finding an optimal configuration for flood defence systems based on an economic cost-benefit analysis with an arbitrary number of interdependent flood defences. The proposed approach is based on a graph algorithm and is, thanks to some beneficial properties of the application, able to represent large graphs with strongly reduced memory requirements. Furthermore, computational efficiency is achieved by delaying cost calculations until they are actually needed by the graph algorithm. This significantly reduces the required number of computationally expensive flood risk calculations. In this paper, we conduct a number of case studies to compare the optimal paths found by the proposed approach with the results of competing methods that generate identical results. The proposed approach is set up in a generic way and implements the shortest-path approach for optimising cost-benefit analyses of interdependent flood defences with computationally expensive flood risk calculations.

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.