An Integrated Framework for Multi-Hazard Vulnerability Assessment in Coastal Deltas

Deltaic systems, which are critical global hubs of population, economic activity, and biodiversity, face escalating threats from climate change. Conventional vulnerability assessments, often focused on single hazards, fail to capture the complex, interacting nature of coastal risks, leading to fragmented and potentially maladaptive policy responses. This paper introduces a novel, replicable Integrated Coastal Impact Index (ICII), a composite framework that synthesizes multiple biophysical and ecological impact indicators—including erosion, flooding, saltwater intrusion, and abiotic stress—derived from high-resolution climate projections and detailed coastal characterization data. The framework is applied to Egypt's Nile Delta coast, a globally significant and highly vulnerable socio-ecological system. The results identify distinct "multi-hazard hotspots" where risks of physical degradation and ecosystem collapse converge. Analysis of future climate scenarios reveals a significant intensification and spatial expansion of these hotspots through to 2070, particularly under the high-emissions RCP8.5 pathway. This study's unique contribution is a transferable, evidence-based tool that advances coastal resilience assessment by enabling a more holistic understanding of compounding climate impacts. It provides a robust scientific foundation to inform adaptive governance, prioritize investment, and operationalize Integrated Coastal Zone Management (ICZM) in the Nile Delta and other climate-stressed deltas worldwide.