Transdisciplinary co-design to assess impacts of climate change on coastal schemes.

Coastal hazards pose a significant risk to people, property, and infrastructure worldwide. They will be increasing over the next century mainly driven by sea level rise. Managing the coast in a sustainable way requires understanding the impacts under a changing climate of actions done and decisions taken now. This often relies on exploring the response of coastal systems to changing natural and/or anthropogenic drivers using modelling tools. The experimental design of such modelling work is essential in providing the robust scientific evidence needed to underpin effective coastal management. Yet, this experimental design often remains rooted within disciplinary silos and may not take a holistic view of the whole coupled human-environment coastal system. We will explore how considering whole coastal social-ecological systems and social acceptance can shape the experimental design of modelling coastal impacts under a changing climate, and lead to better scientific evidence. We will present a new integrated, transdisciplinary system-based framework that brings together the provision of a conceptual representation of the complex coastal social-ecological system and consideration of key drivers in this, modelling coastal flooding and valuing ecosystem services now and into the future, and the influence of social perceptions and values. We will illustrate our approach with case studies across the United Kingdom. We will also discuss the benefits and challenges of following a transdisciplinary approach with respect to common coastal managements ambitions, such as improving coastal resilience, promoting a transition towards greener nature-based solutions, and following national and/or global net-zero and net gain objectives. Our case studies span a range of coastal systems across three nations of the United Kingdom in order to provide examples of different policies and interventions as well as different environmental drivers. Our work builds on the outcomes of a transdisciplinary capacity-building workshop, which highlighted the need for robustness, consistency, and communication when developing modelling scenarios. We use Fuzzy-Cognitive Mapping to elicit maps of generic coastal social-ecological systems. This is complemented by Soft System Modelling of coastal scheme decision making. We use questionnaire surveys and focus groups combined with Q-sort methodology to define and rank key factors in social acceptability of coastal schemes. Numerical modelling of coastal flooding relies on nested implementations of DELFT3D and SFINCS (Super-Fast INundation of CoastS) models for our case studies. Economic assessment and cost benefit analyses are grounded in the CICES framework and use GIS for habitat mapping to identify the extent and value of various habitats and assess potential flood losses. Overlaying social and flood maps for different scenarios ensures a thorough understanding of impacts, aiding informed decision-making. This approach integrates current habitat conditions with future change projections, essential for effective environmental management and policy planning. Applying these methods for our case studies, and bringing them together via morphological analysis, our results show that Fuzzy-Cognitive Mapping, Soft System Modelling, Q-sort, and focus groups all provide valuable information and change the optimal output of the experimental design and selection of scenarios. The outcome is that the scientific evidence produced becomes more useful, useable, and trusted.