Flash Flood Kills Thousands in Libyan Port City

Flooding in Derna
Courtesy Libyan Red Crescent

Published Sep 12, 2023 9:26 PM by The Maritime Executive

As Storm Daniel swept towards the Libyan coastline last week, local authorities closed down four major oil ports as a precautionary measure - but they could not anticipate the string of catastrophic events that would follow at the small port city of Derna.

As the storm came ashore Sunday, it began to dump rain onto the hills just inland from this seaside city of 100,000 people. The water funneled into a narrow ravine, Wadi Derna, which leads down towards the center of the city. When two dams upstream burst, it overflowed its banks - suddenly and catastrophically. 

Five bridges were destroyed and whole blocks of apartments were washed away as the river scoured a broad channel through Derna's downtown core. Satellite imaging and bystander photos show that silt and debris from the flooding washed up much farther on either side of the river, reaching the small seaport complex on the city's eastern edge. 

The death toll estimate for Derna rose to 2,000-5,000 on Monday. Another 46 fatalities have been reported dead in the town of Bayda, and 15 more in other nearby coastal communities. Thousands more have been reported missing - including, tragically, dozens of relief workers who had gone in to help those affected by the floods.

"In terms of aid items, the top request emanating from Derna right now is body bags, according to a Benghazi surgeon," said RUSI associate fellow Jalel Harchaoui in a social media post.  

Eastern Libyan official Essam Abu Zeriba told Al-Arabiya that many of the missing may have been swept out to sea by the onrushing water - further lowering the odds of survival.

The full extent of the damage will take time to establish. Libya's split administration may also complicate the response: after a decade of civil war, the nation remains split between rival governments in the east and the west. The two governments have issued competing assessments of the casualty count and situation on the ground.  

Satellite imaging shows complete destruction at Wadi Derna's two dam sites. The dams were built in the 1970s under the government of then-president Muammar Ghaddafi, and a Yugoslavian engineering firm advised on the construction, according to Serbian consultancy Hidrotehnika-Hidroenergetika. Both were embankment dams with clay fill, and taken together they had a storage capacity of about 20 million cubic meters (about five billion gallons). 

The most common earthen dam failure mode is overtopping, where floodwaters rise over the dam and erode it away. Older dam designs may be more vulnerable to this risk today, as maximum flood height predictions have increased in many regions in recent decades, according to the U.S. Army Corps of Engineers.