A new USC study reveals a dramatic rise in building collapses in Alexandria, Egypt, as rising sea levels and seawater intrusion erode the city’s foundations. Once a rare occurrence, collapses have surged from about one per year to 40 annually over the past decade, threatening one of the world’s oldest coastal cities.
Researchers found that even minor sea level rises are destabilizing Alexandria’s dense urban landscape, which has withstood centuries of earthquakes, storms, and invasions. The study, published in Earth’s Future, also highlights similar risks facing California’s coastal cities, where land subsidence and saltwater intrusion are worsening flood risks.
Using historical maps, satellite imagery, and isotope analysis, scientists tracked Alexandria’s shoreline retreat and discovered that seawater intrusion is undermining buildings from below. “It isn’t the buildings themselves, but the ground underneath them that’s being affected,” said soil radiation scientist Ibrahim H. Saleh of Alexandria University.
To counteract coastal erosion, researchers propose nature-based solutions such as sand dunes and vegetation barriers to block seawater and stabilize groundwater levels. “Protecting Alexandria isn’t just about saving buildings; it’s about preserving our shared human heritage,” said USC scientist Essam Heggy. The findings serve as a stark warning that climate change is already reshaping historic coastal cities worldwide.
