Climate-resilient systems prioritisation index: a spatial framework for multi-hazard mitigation via nature-based solutions

This article presents the Climate-Resilient Systems Prioritisation Index (CRESPI), a GIS-based spatial decision-support framework developed to support climate resilience planning through the prioritisation of Nature-based Solutions (NbS). Grounded in a Complex Adaptive System of Systems (CASoS) perspective, CRESPI conceptualises landscapes as interdependent socio-economic, ecological and infrastructural systems. Resilience is operationalised through the analysis of Key Community Systems (KCS), including infrastructure, mobility, social and health services, economic activities, populations, and ecosystems. CRESPI integrates flood exposure with indicators of social vulnerability, infrastructure criticality, economic sensitivity, and ecological context. Pluvial and fluvial hazards are represented using flood-depth data, while system interdependencies are identified through spatial convergence analysis. Indicator weighting is implemented using the Analytic Hierarchy Process (AHP), following a protection-oriented rationale that prioritises human safety, service continuity, and compound risk conditions. All indicators are aggregated within a 100 m² hexagonal tessellation, selected to support fine-scale spatial differentiation across the different landscapes. The framework is demonstrated in the Arrondissement of Ostend (Belgium), an area exposed to pluvial and fluvial flooding. Results identify spatial hotspots where multiple system vulnerabilities converge. By intersecting these priority zones with NbS suitability layers, CRESPI supports identification of locations where NbS can reduce flood risk while delivering ecological co-benefits.