Dam failures intensified 2023 flood tragedy in Libya
Satellite data and models found dam failures, rather than unprecedented rainfall, led to increased flood damage
The devastating 2023 flood in the port city of Derna, Libya, was driven by the collapse of two dams rather than by extreme rainfall, according to a new study. The destructive flood swept away entire neighborhoods, over 1,000 buildings, and claimed over 5,000 lives.
The new research challenges the idea that this disaster was an unavoidable natural event and instead demonstrates that poor infrastructure planning played a crucial role in the devastation.
CIRES Visiting Fellow Yuval Shmilovitz collaborated with researchers from The Hebrew University of Jerusalem and the University of Haifa to study the causes of the flood and the resulting destruction in the city of Derna. The team found that while Storm Daniel, a Mediterranean tropical-like cyclone, brought heavy rainfall, the catastrophe stemmed from the failure and false sense of security from the dams upstream that encouraged building and habitation in vulnerable areas.
The study, published Friday in Science Advances, sheds light on the catastrophic flood and highlights the urgent need for improved flood mitigation strategies, especially in dry regions.
“Our findings reveal that the Derna disaster resulted from inadequate dam planning rather than an unprecedented extreme storm,” Shmilovitz said. “An alternative flood prevention strategy or properly designed dams could have significantly mitigated the tragedy. This disaster is a stark warning about the risk of over-reliance on infrastructure in areas where weather variability challenges planning.”
In their new study, the research team used satellite observations and hydrological models to reconstruct the sequence of events leading to the flood and the role of the structural failure of two embankment dams, which were designed to hold back water in Wadi Derna, upstream from Derna, on the subsequent destruction of homes and buildings.
Simulated discharge, depth, and SP under the dam breach and no-dams scenarios.
Maximum depth differences between the two scenarios (left) and the SP simulated for the breach scenario. In most of the flooded area, the SP of the breach flood is 2 to 100 times larger than the SP of the no-damsflood.
Their findings reveal that while the rainfall intensity was high, it was not an unprecedented event. Instead, they show that storms of similar magnitude to Storm Daniel—and the resulting flood—are expected in the region once every few decades.
Hydraulic simulations show that if the dams had not been built, the flood’s impact on Derna would have been significantly lower. When the dams collapsed, the resulting flood surge caused severe destruction, twenty times more than the damage would have been had the dams not been built.
The study highlights the urgent need for improved risk assessment and flood mitigation strategies, particularly in dryland regions where extreme weather variability is common, according to the authors The researchers emphasize that over-reliance on flood protection infrastructure without proper risk communication can lead to catastrophic failures. Instead, they advocate for nature-based flood prevention solutions and robust early warning systems to better protect communities from similar disasters.
“The lessons from Derna strongly imply that the failure of other dams around the globe is not a matter of if, but rather when,” Shmilovitz said. “Mitigating this timely hazard requires re-evaluation of habitat planning along streams, considering the natural variability of weather events and possible failure scenarios that should be communicated to the public.”
This story was adapted from The Hebrew University of Jerusalem’s press release.
