Claudia Gazzini

A Natural or Preventable Disaster?

In the aftermath of massive flooding that killed some 20,000 people, Crisis Group expert Claudia Gazzini travelled to Libya to look into what caused the disaster and who might bear responsibility.

After visiting Derna and witnessing the devastation caused when the city’s two dams crumbled in the early hours of 11 September, I decided to see what remains of the largest of the barriers, the Wadi Bu Mansour Dam.

It was the collapse of this dam and another smaller one on the city’s outskirts, known locally as Sadd al-Bilad (City Dam), that turned the flooding of Derna into a human tragedy. I wanted to understand what happened that night and why the dam did not withstand the torrential rainfall that the huge Mediterranean storm named Daniel had unleashed on eastern Libya the day before.

To reach the source of the deluge requires a major detour, because the road that flanks the valley and connects it to the city was wiped away along with everything else in its vicinity. As a result, a journey of what would have been 13km is now more than seven times as long. An old Libyan friend from the area accompanied me when I went.

We drove south from Derna into the desert and then slowly made our way through the barren hills and deep valleys of the Green Mountains. We passed a checkpoint called Bawaba al-Nuwar, which has an ignominious past: when Islamic State militants controlled Derna between 2014 and 2016, guards killed many military officers who were travelling along the road connecting Tobruk to Benghazi. A row of rocks was blocking the last stretch of asphalt leading to the dam, but we managed to manoeuvre around it.

I wanted to find out why this dam built by a Yugoslav company in the mid-1970s fell apart. Libyans, rightfully outraged by the calamity that killed an estimated 20,000 people (with thousands still missing), have blamed politicians for failing either to properly maintain the dam or to give orders in time for Derna residents to evacuate, even though they knew that a dangerous storm was headed toward the city. 

There are other theories circulating about the collapse. Some Derna residents say the dam’s valves were not open when Daniel hit, which would have made it much more vulnerable to failure in a storm of that magnitude. There are also troubling allegations about politicians embezzling funds earmarked for the dam’s renovation.

Which official Libyans single out for censure often depends on which side they pledge allegiance to in the country’s fragmented political system. Since 2022, the administration has been split between an internationally recognised government headed by Abdelhamid Dabaiba based in Tripoli, and its rival in eastern Libya, led by Osama Hamad.

It is the Hamad government, backed by Field Marshal Khalifa Haftar’s Libyan National Army, that oversees the east and has control of Derna. Western Libyan activists opposed to Haftar point their fingers at him and his forces. In turn, Haftar’s forces tend to scapegoat Derna’s former mayor, who is related to the east-based parliament speaker, Aghila Saleh. Both men come from the Derna area. Saleh backs the east-based government, and is nominally a Haftar ally, but he has been at loggerheads with the field marshal over the past year.

For their part, Tripoli-based Islamists intimate that Egypt (which backs Haftar) blew up the two dams intentionally, though I have seen no evidence supporting this charge. No matter which side they fall on, most ordinary Libyans are inclined to blame some combination of neglect and malfeasance, rather than solely forces of nature, for the disaster.

At the Site

When I arrived at a cliff overlooking Wadi Bu Mansour, it dawned on me what may have happened that terrible night. Below lay a valley at least 200m deep that descends from the south and continues to the north. It is a dry valley, which collects water only when it rains. I could see just the last 10km of it, but I knew from maps that upstream it goes on for at least another 100km to the west, running roughly parallel to the Mediterranean coast.

At the bottom of the valley, I detected what remained of the dam: a clay mound that used to be covered with rocks. (More technically minded people called the Wadi Bu Mansour structure a clay-injected embankment dam.) Water smashed through the central part, breaking up the road that ran along the top of the dam. Experts say this type of clay-and-rock dam is quite sturdy, but its foundations are vulnerable to the eroding effects of overflows, especially when it is built on a clay base, as appears to have been the case here.

Eyewitnesses told me the flood seemed to come out of nowhere. “At sunset, the valley was still dry”, a young man who lives nearby said. He was referring to a valley that descends at least 200m and feeds into Wadi Bu Mansour. The dam’s security guard joined us and gave a recitation of that evening’s events that confirmed what the young man said. “The dam started filling up around 8pm, but at midnight it was only half-full.

It was between midnight and 2am that [the water] started rising at a dangerous speed. By 2am, the water reached 2m above the dam, pouring over to the other side. That gradually weakened the dam’s structure, causing it to collapse”, he said. “We could hear the friction of the rocks as they gave way, which also left a peculiar smell of burnt material in the air”. The dam finally caved in at 2:40am.

The guard added an important data point to this description. The valves of the dam’s passageways were open – and had been since the 1990s. Later, I spoke by telephone to his boss in Derna, Abdullah Tunisi, who is in charge of the dams in the valley; subsequently, I spoke with Tunisi’s superior in Benghazi, Abdelqader al-Sweisi, who administers all the dams in eastern Libya. Both work under the authority of the Tripoli-based government’s water ministry.

They both asserted that the valves had been open since the 1990s. Tunisi explained that the dam was originally conceived for irrigation, but in the late 1980s officials realised it had structural problems (as water was leaking from underneath it, creating a new canal), and so they stopped using it to retain water. For this reason, the valves were left open.

If the valves were in fact open, that would undermine the allegation that has circulated in Derna pinning some of the blame for the calamity on the dam operators. A number of Derna residents, however, say they do not believe the valves were open. They claim that local farmers closed the valves to irrigate pomegranate trees at the base of the dried-up wadi below the dam.

I am not in a position to determine who is correct, but according to the Tripoli-based water ministry’s calculations, the dam was doomed no matter how it had been operated. Up to 100 million cubic metres of water may have filled the valley that night.

The pressure it generated eventually led the dam, which is designed to retain no more than 22 million cubic metres of water, to collapse. Sweisi told me that the total water discharge capacity of the dam is 170 cubic metres per second but, that night, “we calculated that to discharge all the water entering the valley would have required a discharge capacity of 1,200 cubic metres per second”. In essence, according to their calculations, what befell Derna was a natural disaster rather than one of human provenance.

One point upon which there appears to be widespread agreement is that almost no one in Derna or in the dam’s vicinity saw the calamity coming. Just a few days before the storm, a group of Derna residents met to discuss how to protect themselves.

A person who attended the meeting said no one seemed overly alarmed. “It was a theoretical, hypothetical discussion”, he said. “It did not prompt anyone to alert the authorities and warn of serious danger of collapse”.

A few days later, I met Abdelmonem al-Gaithi, the mayor of Derna who was fired in the storm’s aftermath, in a hotel lobby in al-Bayda, a city to the west. (Four days after our meeting, he was arrested and taken into custody.) During our meeting, he claimed that “nobody in the city had suggested to us that the storm could cause the dam to collapse”.

Furthermore, in the days before the storm struck eastern Libya, the local authorities’ principal concern was Benghazi, the region’s main city, which lies in what was Daniel’s predicted path. Instead, the storm unexpectedly turned east, leaving Benghazi relatively unscathed. He also rejected the claim that the Derna municipal council he headed bore any responsibility for the dam’s maintenance. “Dams are strategic sites, and they come under the authority of the competent ministries, not of the local council”, he said.

In Derna, the greatest fear before the storm was that it could damage the seafront residential area. “We thought the danger would come from the sea”, al-Gaithi said. Residents were also bracing for a possible overflow of the dams – something they had experienced already twice before – but not the dams’ actual collapse.

The mayor nevertheless insisted that the city’s emergency committee set up three days before the storm had given orders to evacuate the three neighbourhoods (Sayda Khadija, Heyy al-Bilad and Jebeila) most at risk of flooding because they were on lower ground. On social media there are videos that show policemen in their vehicles instructing people to leave. “Unfortunately, few heeded the warning”, the mayor told me.


Claudia Gazzini is the International Crisis Group’s Senior Analyst for Libya. She has covered this role since 2012. 


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