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.

Increased climate impacts threaten coastal functions globally, highlighting the need for multifunctional coastal climate adaptation. Sand nourishment can adapt sandy coasts to sea level rise, mitigate erosion, increase flood safety, enhance ecological habitats and expand recreational space. Therefore, sand nourishment is increasingly regarded as a promising nature-based strategy for coastal climate adaptation. However, despite this growing recognition, the assessment of how sand nourishment design impacts multifunctional adaptation remains limited. In this perspective article, we argue for three key lessons for researchers to optimise assessing multifunctional coastal climate adaptation by sand nourishment. We conducted stakeholder workshops to scope and inform our perspective, performed semi-structured literature reviews to concretise and validate this for international applications, built a qualitative model to visualise our interdisciplinary overview of how nourishments impact coastal multifunctionality, reflected on this in expert workshops, and identified implications for researchers. In this manner, we assessed the effects of nourishment design on coastal morphology, ecology, socio-economics and ecosystem services in realising the key policy goals of flood safety, nature and recreation. We found that sand nourishment design can result in conflicts between policy goals, generate ambiguous outcomes and lead to system-wide feedback effects. As such, we identified three key lessons: (1) conflicts between policy goals require informing political decision-making on prioritisation between coastal functions, (2) concreteness is needed on otherwise ambiguous functions, and (3) ongoing, multidisciplinary system-wide monitoring is essential. We thus call for a holistic approach to sand nourishment design and encourage researchers from diverse expertise and localities to expand on and adapt our findings to optimise informing sand nourishment design for delivering multifunctional coastal climate adaptation worldwide.