A Multi-Hazard Physical Diagnosis of Climate Risk for Urban Sustainability in Alexandria, Egypt

As a low-lying coastal metropolis on the Nile Delta, Alexandria, Egypt, is a recognised global hotspot of climate change vulnerability. This study presents a novel, multi-hazard physical diagnosis of the Alexandria Metropolitan Region (AMR) to quantify the compounding risks posed by climate change to its urban system. The methodological framework integrates climate projections, hydrodynamic modelling, and morphodynamic analysis to assess seven key climate-related drivers: erosion, flooding, saltwater intrusion, abiotic stress, drought, heat waves, and port downtime. The diagnosis is conducted across three temporal horizons (Present, 2030–2040, and 2050–2070) and two Representative Concentration Pathways (RCP 4.5 and RCP 8.5). The results reveal a significant amplification of climate risks, with the high-emissions RCP 8.5 scenario projecting a systemic degradation of coastal stability. Key findings include a projected shift from medium to high erosion risk across the urban waterfront, a near-complete exposure of the urbanised coastline to high flood risk by mid-century, and escalating threats from saltwater intrusion into the coastal aquifer. These compounding physical pressures threaten critical infrastructure, urban housing, and coastal ecosystems. The findings underscore the inadequacy of static, hard-engineered coastal defences and highlight the urgent need for a paradigm shift towards adaptive, risk-informed coastal management. This study's significance lies in its provision of a replicable diagnostic framework and its translation of physical science into actionable policy recommendations for urban sustainability, including the integration of nature-based solutions and climate-adaptive spatial planning, aligned with Egypt's national climate and development strategies.