For years it had been clear that the dams protecting Derna, on Libya’s Mediterranean coast, were in danger of giving way.
Torrential rains were not new. Decade after decade, they had scourged the area, washing away the earth that helped absorb the water that ran from the dry hills above the city.
Climate change had also changed the land, making it drier, harder and increasingly devoid of vegetation, less able to absorb water before it pooled dangerously behind dams.
Then there were the decades of negligence by officials (who knew the dams needed repairs) in a country so torn by years of civil war that it still has two opposing governments: one in the west and one in the east, where Find Derna.
Academics had warned that it would not take a storm of biblical proportions to wipe out the dams.
Derna residents are “extremely vulnerable to flood risk,” wrote Abdelwanees Ashoor, a hydraulic engineer at Omar Al-Mukhtar University in Libya, in a paper he published in 2022.
The type of storms that had hit the area in recent decades (he cited a damaging flood in 1959) could topple the dams and flood Derna, he warned, calling the situation “dangerous.”
Last week, those predictions proved true, when massive flooding caused by a powerful storm breached both dams and swept parts of the city into the sea. According to authorities, there are thousands dead and many more missing. According to the International Organization for Migration, more than 34,000 people were displaced by the disaster.
Reached by phone, Dr Ashoor said he had lost several members of his family in last week’s floods, adding that the government had ignored years of warnings, including from his own newspaper.
“We are living in shock. We cannot absorb what is happening to us,” Dr Ashoor said. “The State was not interested in this. Instead, they squandered money, engaged in corruption, and waged political disputes.”
The dams were built by engineers who underestimated the amount of rain expected in the region, he said. To make matters worse, the land had undergone a process of desertification, making it less porous and able to absorb runoff. Beyond that, local officials say the dams have received little maintenance since their construction in the late 1970s.
Dr Ashoor said he had sent his paper to academic colleagues in the country’s capital, Tripoli, and a US dam expert said his conclusions seemed sound.
“He did it,” said Michael W. West, retired principal of the engineering firm Wiss, Janney, Elstner. “His main point is that the hydrological design of those dams was inadequate and they could not withstand large storms.”
“It’s probably devastating to know that he was right, plus the personal tragedy that comes with it,” West added. “I can’t imagine how it feels.”
Libya, an oil-rich nation on the shores of the Mediterranean, has been worn down by years of civil war and misrule. Climate change has only increased tension, contributing to once fertile terrain becoming arid and desolate.
According to experts, the two dams overlooking the city were built with the help of engineers from the former Yugoslavia. The largest, known as Abu Mansour, was 74 meters high and could hold up to 22.5 million cubic meters of water. The smallest, al-Bilad, or simply Derna Dam, was built on the outskirts of the city.
During the long, autocratic reign of Colonel Muammar Gaddafi, floods came and went, but the dams remained standing. In 1986, a major storm hit the region, damaging dams and ripping dirt from the ground. The structures were damaged, Dr. Ashoor said, but again held up.
Despite the tensions, repairs were minimal. In 1998, the Libyan government commissioned a study that revealed cracks and fissures in the dams, Attorney General Sadiq al-Soor said.
Almost ten years later, a Turkish company was finally hired to repair the dams, the prosecutor added. But the government was slow to pay and the project was not launched until 2010, al-Soor told reporters on Friday.
Just four months later, in 2011, The Libyans marched against of Colonel Gaddafi Control of power for 42 years, inspired by the uprisings that had overthrown Arab autocrats in Tunisia and Egypt. When he threatened to annihilate the opposition, NATO intervened and bombed his forces, with the United States as the backbone of the operation. Colonel Gaddafi was expelled from Tripoli in August of that year.
Amid the tumult, work on the dam ceased, the prosecutor said.
He vowed that authorities would take “firm action” against anyone deemed responsible for failing to properly maintain the two dams. “This is extremely important to protect the rights of victims and determine who was responsible, whether there was negligence or breach of duty,” Mr al-Soor said.
He said authorities had appointed prosecutors from different parts of Libya to investigate what caused the dams to collapse, inspect homes and determine whether maintenance measures could have prevented the disaster.
More than a decade after the chaotic overthrow of Colonel Gaddafi, the country remains divided between an internationally recognized government in the west and another under Khalifa Hifter, a military commander who controls the east, including Derna.
Derna was a key battleground during the country’s civil war, in which the city fell under the control of Islamist militias. After a prolonged siege, forces loyal to Hifter declared victory in 2018, although skirmishes continued for several months.
Meanwhile, the abandonment of the dams continued.
According to a 2021 report by Libyan state auditors in the west of the country, more than $2.3 million allocated for maintenance of the two dams was simply never used. They called it a case of government negligence.
And as recently as last week, less than two days before the dam burst, a Libyan nonprofit, Roya, wrote on Facebook that the dam could fill to bursting during the powerful storm that hit the Mediterranean.
“We ask residents of the valley to be very careful,” the group said.
Even as the waters rose, some officials, far away in Tripoli, saying shortly after midnight on Monday that the dams were in “good condition” and that there was “no cause for concern about collapse.” They added, however, that the storm had affected their ability to contact those in charge of monitoring one of the dams.
Very soon after, well before dawn, the rising waters appear to have overwhelmed the dams: first the largest Abu Mansour dam, then the second, smaller one downstream, which was destroyed in a matter of “moments,” said Dr. .Ashoor.
The tide devastated large areas of the city, destroying roads and bridges, sweeping away cars and destroying apartment buildings, witnesses said.
Entire families died, officials say, drowned or trapped under rubble. Others were swept out to sea.
William F. Marcuson III, former president of the American Society of Civil Engineers, said these dams, which were made of clay and rock, were common around the world.
“There’s nothing wrong with that approach, if done correctly,” he said. But, he added, dams must be designed for the maximum likely storms and built under careful inspection so that no shortcuts are taken.
The dams included concrete spillways that are supposed to work much like an overflow drain in a normal bathtub: if the water rises too high, it enters the spillway, runs down underground pipes, and is discharged below the dam.
But if the spillway is not big enough or the pipes are too narrow for the force of the storm, the water continues to rise.
When it rises above the top of the dam, called “overtopping,” the dam itself begins to erode. As that happens, the embankment supporting the dam gradually erodes until the entire structure fails and water flows freely.
If the upstream dam failed first, a wall of water may have washed away the lower dam with alarming speed.
With no further obstacles in its path, the water crossed the countryside, fanning out for dozens of kilometers. The main force of the raging torrent slid into the natural funnel of the Derna River basin, where residents say they received confusing, sometimes contradictory, orders about evacuation.
In a televised speech Thursday, Aguila Saleh, speaker of parliament in the east of the country, sought to reject accusations that the extent of the devastation was due to government mismanagement and negligence.
“Don’t say, ‘If only we had done this or that,’” Saleh said. “What happened in our country was an incomparable natural disaster.”
Dr Ashoor acknowledged that the flood was caused by a giant storm rarely seen in the country. But he believes authorities could have done much more to minimize the risk.
“Political conflicts, two governments, all the wars we have seen since 2011, terrorism, all the problems we have faced,” Dr. Ashoor said. “All of this came together to lead to this growing disaster, this calamity that we are experiencing. May God alleviate this crisis.”