A recent study reveals that increasing soil erosion in coastal regions due to desertification is intensifying the impact of floods on port cities in the Middle East and North Africa. The researchers particularly examined the tragic floods that occurred in Derna, Libya, in 2023, resulting in over 11,300 fatalities and highlighting how soil erosion aggravated the disastrous effects of these unexpected desert floods. This research was published nearly a year after the catastrophic flood event on September 10, 2023.
A recent study conducted by researchers from the USC Viterbi School of Engineering and the Institute de Physique du Globe de Paris at the University of Paris Cité indicates that rising soil erosion in coastal regions, driven by desertification, is exacerbating flood effects on port cities in the Middle East and North Africa. Concentrating on the devastating 2023 floods in Derna, Libya—which resulted in more than 11,300 deaths—the researchers demonstrated how the escalating soil erosion significantly heightened the destruction wrought by these rare desert floods.
Published in Nature Communications, this research emerged almost a year after the tragic floods that struck on September 10, 2023. The study’s co-authors emphasize that their findings highlight the alarming vulnerabilities faced by arid regions amid the increasing frequency of extreme weather events related to climate change, underscoring the urgent requirement for advanced monitoring programs to scrutinize and characterize these affected areas.
In the last decade, the North African Sahara, which spans an area larger than the continental United States, has been subjected to a perilous blend of circumstances, characterized by escalating aridity interspersed with severe rainstorms along the coast. The root causes include intensifying desertification leading to prolonged droughts and an uptick in rainstorm occurrences linked to rising seawater temperatures in the Eastern Mediterranean, a consequence of global warming. Corresponding author Essam Heggy, a research scientist at the Microwave Systems, Sensors, and Imaging Lab (MiXIL) within the Ming Hsieh Department of Electrical and Computer Engineering and a co-principal investigator at the USC Viterbi Center for Arid and Water Research Exploration (AWARE), states that these two extreme conditions are heightening soil erosion and producing lethal mudflows, which are difficult to manage with the aging dams in the region.
While some experts argue that droughts pose the greatest risk to the Sahara, Heggy contends otherwise, citing evidence from his co-authored paper titled “Assessing flash flood erosion following Storm Daniel in Libya.”
Last year, in Fall 2023, Storm Daniel, also known as “Medicane Daniel,” pummeled Libya’s eastern coast, resulting in unprecedented flash floods that caused over 11,300 fatalities and widespread destruction of infrastructure. Yale Climate Connections suggested that flash floods of this nature had not been observed in Africa for over a century.
The authors clarify that Africa’s deadliest flood in a century, which occurred in a desert setting, was triggered by a combination of factors: abnormally high rainfall, the failure of two flood control dams, and the city’s inadequate water infrastructure to manage such an extreme incident. They propose that sediment loading due to surface erosion increased the water’s density, aggravating the catastrophic effects of the flash floods in coastal cities like Derna and Susah, where 66% and 48% of urban surfaces, respectively, suffered moderate to severe damages.
Utilizing Sentinel-1A C-band orbital Synthetic Aperture Radar images, the researchers tracked changes in signal coherence to assess alterations in surface texture before and after the storm. These measurements serve as indicators for mapping flood damage and evaluating infrastructure impacts.
The research illustrates that the flow within the streams was heavily laden with eroded soil, which augmented the destructive force of the water flow. This factor ultimately contributed to the failure of two dams intended to safeguard Derna’s residents.
Heggy acknowledges that current runoff flow models are useful for estimating flood extents but insufficient for evaluating surface erosion in desert settings, which can lead to devastating consequences, as witnessed in Derna.
Advanced radar satellites, according to Heggy, can bridge this gap. “Enhancing the monitoring of arid watersheds through sophisticated radar satellites is vital for mitigating these severe risks across various regions of the Sahara, the Arabian Peninsula, and other deserts.”
Jonathan Normand, a visiting graduate student at the USC AWARE Center and the lead author of the study, points out, “In today’s world, you can easily post on social media from anywhere, even the middle of a desert, thanks to the numerous communication satellites in orbit. However, researchers still rely on a limited number of satellites to understand the complexities of Earth’s dynamics and surface processes in desert environments.”
“The events that unfolded in Libya could potentially occur in many densely populated regions throughout North Africa and the Arabian Peninsula,” warns Heggy, with support from colleagues in tandem studies conducted with researchers from Morocco and Spain.
Heggy notes additional risk factors: storms are intensifying, while urban areas are becoming more populated and less organized regarding policies aimed at minimizing development and enhancing disaster preparedness.
“The tragic floods in Derna demonstrate that regional decision-makers in the Middle East and North Africa may not be heeding scientific findings adequately, despite hosting the last two climate change conferences in the region. Our most formidable adversary ahead is the unwarranted belief that these extreme events are isolated incidents that won’t recur. Climate models warn that stronger events will follow.”
