A new study in Earth Future finds a sharp rise in building collapses along Alexandria’s coast and warns the area is now the most at-risk part of the Mediterranean Basin. Over the past 20 years more than 280 buildings have collapsed, and the collapse rate is about ten times higher than in earlier decades. The study says more than 7,000 buildings in the most vulnerable zone face risk.
The researchers, led by Essam Heggy of the University of Southern California, attribute the damage mainly to severe coastal erosion and rising sea levels linked to climate change. Seawater intrusion into groundwater raises water and salt levels in soil, which destabilises the ground and accelerates corrosion of foundations. The team used geographic, geological and engineering data, government reports, news archives, satellite imagery and topographic maps. A soil settlement analysis noted a link between poor soil stability and increased collapses; the Gharb district has seen the shoreline retreat by an average 31 metres a year over the last century.
The study lists other human factors, including over-extraction of groundwater, land reclamation, lack of maintenance, weak sewage systems and weak coastal legislation. It warns that cities such as Tunis and Tripoli face similar risks and notes that building collapse rates along Italy’s southern coast rose by nine per cent over the past two decades.
Authors propose nature-based "soft defence" measures and technical solutions. Suggested actions include:
- living beaches, breakwaters and wetland restoration
- rain gardens and a green street network with salt-tolerant plants
- sea walls, flood barriers and restoration of mangroves and coral reefs
- relocation of vulnerable communities and stricter coastal development rules
Difficult words
- collapse — sudden fall or failure of a structurecollapses, collapsed
- erosion — gradual wearing away of land or soil
- seawater intrusion — movement of seawater into freshwater underground
- groundwater — water located under the earth's surface
- corrosion — chemical or physical wearing of materials
- reclamation — process of creating land from sea or wetlandsland reclamation
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Discussion questions
- Which of the suggested nature-based or technical measures do you think would be easiest to implement in a coastal city near buildings at risk, and why?
- How might over-extraction of groundwater and weak sewage systems increase the risk of building collapse in coastal areas?
- What social and economic challenges could arise from relocating vulnerable coastal communities?
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