Integrated multi-hazard climate risk across Egypt's water–coast–delta system: reservoir evaporation, coastal inundation, and socio-economic vulnerability

Abstract Egypt’s principal water store, contrasting coastlines and densely populated Nile Delta face climate risks typically assessed separately. We integrate four national assessments within the IPCC AR6 risk framework: Lake Nasser evaporation from pattern-scaled CMIP6 drivers, Red Sea coastal screening, Mediterranean hydrodynamic inundation modelling on a 0.5 m photogrammetric DEM, and a household vulnerability survey across five Delta hotspots (N = 250). By 2100, Lake Nasser evaporation increases by about 8% under SSP2-4.5 and 22–26% under SSP5-8.5, corresponding to bias-corrected incremental losses of 0.7–1.1 and 1.8–3.2 BCM per year (1.3–5.8% of Egypt’s Nile allocation). Along the Red Sea, a 1.10 m screening boundary produces sparse mapped inundation at the survey’s 0.5–1 m resolution, indicating strong topographic control on inland exposure. At Alexandria, an offshore rise of 0.59–0.84 m combined with 2–11 mm per year subsidence yields a screening boundary of about 1.0–1.7 m. A separate nominal 1 m Delta assessment identifies an upper-bound exposure inventory whose farmland irrigation requirement is approximately 2.6–5.4 BCM per year. The synthesis shows that comparable forcing generates distinct reservoir, steep-coast and subsiding-delta risk pathways, supporting differentiated adaptation planning.