Alexandria, Egypt, often celebrated as the “bride of the Mediterranean” for its breathtaking beauty and storied past, is facing an unprecedented crisis. A groundbreaking study from the University of Southern California (USC) has uncovered Egypt’s vanishing coastlines driven by rising sea levels and seawater intrusion. What was once a rare event—approximately one collapse per year—has escalated to 40 incidents annually over the past decade. This frightening trend threatens the physical infrastructure of one of the world’s oldest towns and raises a broader warning about the vulnerability of coastal urban areas globally.

The Causes Behind Egypt’s Vanishing Coastlines

Erosion of Cultural Heritage

As climate change intensifies, the loss of Alexandria’s historic structures underscores a more profound tragedy: the erosion of cultural heritage and human ingenuity that spanned millennia. According to Essam Heggy, a water scientist at USC Viterbi School of Engineering and the study’s corresponding author, even tiny rises in sea level—only a few centimeters—can cause chaos. These slight alterations allow seawater to permeate coastal soils, destabilizing the foundations of long-standing structures.

Rising Collapse Rates

The study finds that Alexandria’s collapse rate has skyrocketed, a phenomenon replicated in California, where sinking ground and seawater intrusion are exacerbating flooding and infrastructure damage. The repercussions of Egypt’s vanishing coastlines extend beyond its borders.

Global Implications

Sara Fouad, a landscape architect at the Technical University of Munich (TUM) and the study’s first author, emphasizes that climate change is undoing centuries of engineering achievements in mere decades. The facts are clear: what was once a distant threat has become a pressing reality that requires immediate response from urban planners and governments worldwide.

The USC study challenges the long-held belief that significant sea level rise—a meter or more—is required to cause widespread damage. Instead, it demonstrates that coastlines, particularly those in the Mediterranean with parallels to California, are already changing dramatically.

The Impact of Coastal Erosion

Alexandria’s diminishing coastline has boosted groundwater levels, allowing corrosive seawater to come into contact with building foundations. This “bottom-up” erosion, as stated by co-author Ibrahim H. Saleh, a soil radiation scientist at Alexandria University, is the underlying cause of the city’s collapsed structures. The findings serve as a wake-up call: coastal erosion is not an issue of the future; it is happening right now, and historic cities are at the forefront of this crisis.

Cultural and Historical Loss

The implications of Alexandria’s vanishing coastlines are severe. With each structural collapse, the city loses not only its physical heritage but also the stories and cultural significance tied to those buildings. As these structures crumble, they take with them the history of a city that has stood for millennia, threatening to erase the legacy of human achievement and resilience.

Innovative Methods to Track the Crisis

Multidimensional Strategy

USC researchers employed a multidimensional strategy combining cutting-edge technology with historical data to assess the depth of Alexandria’s crisis better. The initial stage was to develop a comprehensive digital map utilizing geographic information system (GIS) technology. This map illustrated collapsed buildings in six districts of Alexandria’s old urban heart, one of the city’s most heavily populated neighborhoods. The map covered the years 2001 to 2021 and included information about each building’s location, size, age, construction materials, foundation depth, and number of levels.

Data Collection and Analysis

Data was methodically gathered from site visits, official reports, news archives, and private construction records, providing a comprehensive picture of complete and partial collapses. Next, the team used satellite photos and historical maps (from 1887, 1959, and 2001) to follow the movement of Alexandria’s 50-mile coastline. Their findings revealed that areas of the shoreline have retreated tens of meters inland over the last two decades, a gradual but continuous encroachment that has profoundly transformed the city’s landscape.

Groundwater and Soil Stability

By estimating the rate of retreat over the last century, the researchers showed that the retreating shoreline raises groundwater levels, filling the earth beneath coastal buildings with seawater. This saturation weakens the ground, paving the way for structural failure. The final piece of the jigsaw came from the chemical examination of soil samples. The team measured the mechanical stability of the soil using isotope “fingerprints,” such as the B7 isotope. High B7 levels suggest firm, erosion-resistant soil, whereas low levels indicate degradation.

The findings were startling: seawater infiltration is degrading foundations from below, undermining soil integrity and causing buildings to collapse. This alarming situation highlights the urgent need for innovative solutions to protect Alexandria and other vulnerable coastal cities.

Nature-Based Solutions for Resilience

Long-Term Solutions

The USC study does more than simply diagnose the problem; it also provides realistic, long-term solutions. To combat coastal erosion and seawater intrusion, the researchers propose nature-based solutions such as building dunes and vegetation barriers along Alexandria’s shoreline. These natural defenses would keep the advancing ocean from boosting groundwater levels and destroying foundations.

Cost-Effective and Versatile Strategy

Steffen Nijhuis, a landscape-based urbanist and research co-author at Delft University of Technology, asserts that this strategy is both cost-effective and versatile, making it suitable for highly populated coastal regions around the world.

Improving Urban Life

These interventions have the potential to improve urban life in addition to providing physical protection. The report proposes that Alexandria develop green belts and canals to help control climate extremes while reconnecting citizens with well-maintained public areas.

Architectural Diversity and Community Resilience

Udo Weilacher, a co-author and landscape architect at TUM, believes that conserving the architectural diversity of Mediterranean towns such as Alexandria is more than just a matter of aesthetics; it demonstrates how landscape design can encourage climate-resilient communities. By integrating nature-based solutions into urban planning, Alexandria can not only protect its infrastructure but also foster a sustainable environment for future generations.

Conclusion: A Race Against Time

Alexandria’s plight reflects a global crisis, as the USC study highlights the devastating effects of rising oceans, coastal erosion, and seawater intrusion on the city. Annual collapses have surged from one to 40, signaling escalating losses across coastal regions worldwide. Amid these alarming trends, the researchers present a resilience roadmap, detailing the damage, its causes, and proposing nature-based defenses. The pressing question remains: will the world heed Alexandria’s warning before it, and other historic cities, vanish beneath the waves? Time is running out.

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References

Coastal erosion threatens this ancient city — and others much closer to home

https://today.usc.edu/coastal-erosion-threatens-this-ancient-city-and-others/