This all began when two dams collapsed in the Derna valley during a heavy storm, causing huge amounts of water to race towards the sea and devastate the coastal city.
One expert told Al-Wasat, Libya’s leading news website, that the dams were poorly maintained.
“The security chaos and Libyan authorities’ laxity in carrying out close monitoring of safety measures led to the catastrophe,” claimed expert Mohammed Ahmed.
But the experts we‘ve spoken to say it’s too early to say whether the extreme rainfall was simply too much for the dams to handle or whether the condition of the structures also played a role.
Based on their observations, the dams were likely made from rockfill structures – dumped and compacted soil or rocks – which is not as strong as concrete.
“These dams are susceptible to overtopping [when water exceeds a dam’s capacity] and while concrete dams can survive overtopping, rockfill dams usually cannot,” says Dragan Savic, a professor of hydroinformatics at the University of Exeter.
It appears that the upper dam failed first, likely due to overtopping, according to structural engineer Andrew Barr from the University of Sheffield.
He told us that the water had then likely flowed down the rocky river valley towards the second dam, overwhelming it, resulting in the flooding of the city.