The warnings were clear but went unheeded.

Experts had long said that floods posed a significant danger to two dams meant to protect nearly 90,000 people in the northeast of Libya. They repeatedly called for immediate maintenance to the two structures, located just uphill from the coastal city of Derna. But successive governments in the chaos-stricken North African nation did not react.

“In the event of a big flood, the consequences will be disastrous for the residents of the valley and the city,” Abdelwanees Ashoor, a professor of civil engineering, wrote in a study published last year in the Sabha University Journal of Pure and Applied Sciences.

The warnings came true in the early hours of Sept. 11, when residents of Derna woke up to loud explosions before floodwaters pounded the Mediterranean city. They found that two dams had broken, unleashing a wall of water two stories high that wreaked destruction and swept entire neighborhoods out to sea.

The deluge proved deadly for thousands in just seconds, uprooting apartment buildings and washing away roads and bridges. More than 11,300 people were reported killed, including foreigners, and over 10,000 remained missing a week after the disaster, according to the Libyan Red Crescent and the United Nations.

Neglect and corruption are rife in Libya, a country of about 7 million people that lies on a wealth of proven oil and natural gas reserves. As of 2022, the country ranked 171 out of 180 on the transparency index compiled by Transparency International.

The North African nation has been in chaos since 2011, when an Arab Spring uprising, backed by NATO, ousted longtime dictator Moammar Gadhafi, who was later killed.

The country has since divided between rival administrations: one in the west backed by an array of lawless armed groups and militias, and the second in the east allied with the self-styled Libyan National Army, which is commanded by powerful Gen. Khalifa Hifter.

The dams, Abu Mansour and Derna, were built by a Yugoslav construction company in the 1970s above Wadi Derna, which divides the city. Abu Mansour, 14 kilometers (8.6 miles) from the city, was 74 meters (243 feet) high and could hold up to 22.5 million cubic meters of water. The Derna dam, also known as Belad, is much closer to the city and could hold 1.5 million cubic meters of water.

#Libya was mired in chaos and corruption. For years, warnings the #Derna #dams may burst went unheeded. #LibyaFloods

The dams, built from clay, rocks and earth, were meant to protect the city from flash floods, which are not uncommon in the area. Water collected behind the dams was used to irrigate crops downstream.

“Both dams had not been maintained for many years, despite repeated floods that struck the city in the past," said Saleh Emhanna, a geological researcher with the University of Ajdabia in Libya. “They were dilapidated.”

The dams suffered major damage in a strong storm that hit the region in 1986, and more than a decade later a study commissioned by the Libyan government revealed cracks and fissures in their structures, Libya's general prosecutor, al-Sediq al-Sour, said late Friday.

At a news conference in the stricken city, al-Sour said prosecutors would investigate the collapse of the two dams, as well as the allocation of maintenance funds.

“I reassure citizens that whoever made mistakes or negligence, prosecutors will certainly take firm measures, file a criminal case against him and send him to trial,” al-Sour said.

A report by a state-run audit agency in 2021 said the two dams hadn’t been maintained despite the allocation of more than $2 million for that purpose in 2012 and 2013. No work was done in the area, and the audit agency blamed the Ministry of Works and Natural Resources for failing to cancel the contract and give it to a company that would do the work.

A Turkish firm was contracted in 2007 to carry out maintenance on the two dams and build another dam in between. The firm, Arsel Construction Company Ltd., says on its website that it completed its work in November 2012.

Arsel was one of dozens of Turkish companies that had projects worth more than $15 billion in Libya before the 2011 uprising. Many of these companies fled the Libya chaos before returning in the past couple of years, especially when the Turkish government stepped in to help the Tripoli-based government fend off an attack by Hifter's forces in 2019.

Arsel didn’t respond to an email seeking further comment on the two dams. No third dam appeared to have ever been built, recent satellite photos show.

Ahead of Mediterranean storm Daniel, authorities also gave contradicting messages. They imposed a curfew in Derna and other areas in the east. The municipality of Derna published statements on its website urging residents to evacuate the coastal areas for fear of a surge from the sea.

However, many residents said they received text messages on their phones urging them not to leave their homes.

The floods flattened Derna and officials have estimate that as much as a quarter of the city has been erased. Such devastation reflected the storm’s intensity, but also Libya’s vulnerability. The country’s infrastructure has suffered widespread neglect despite Libya’s oil wealth.

Al-Sour, the chief prosecutor, said prosecutors would probe local authorities in Derna as well as previous governments. He appointed investigators from different parts of the country to carry out the investigation.

East Libya's government suspended Derna’s mayor, Abdel-Moneim al-Gaithi, pending an investigation into the disaster. The mayor didn't respond to phone calls seeking comment.

Since 2014, eastern Libya has been under the control of Hifter and his forces. The rival government based in the capital, Tripoli, controls most national funds and oversees infrastructure projects. Neither tolerates dissent.

Activists are calling for an international probe, fearing that a local investigation would be fruitless in a country largely ruled by armed groups and militias. The “predatory” behavior of these groups and militias has resulted in “the misappropriation of Libyan State funds and the deterioration of institutions and infrastructure,” according to a report by the U.N. panel of experts.

Libya has suffered from weak public institutions, internal conflict and deep instability, which allowed corruption to become rife with few to no checks on public sector abuse, according to Transparency International.

An online petition signed in recent days by hundreds of people, including Libyan rights groups and NGOs, said an independent international committee is needed to “uncover the causes of this catastrophe” and hold those responsible accountable.

Jalel Harchaoui, an expert on Libya at the London-based Royal United Services Institute for Defence and Security Studies, said an investigation into the disaster would face towering challenges since it could reach top officials in west and east Libya.

Such an inquiry “might potentially reach into the highest ranks of responsibility,” he said. “This presents a unique challenge.”

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A couple of observations, because the rush to finger-pointing on this disaster risks exceeding the hype of Barbenheimer.

First, if you're following this story and haven't yet done so, review the satellite images of the former dams:

1. Upstream

2. Downstream

Now, while I have a very strong mechanical aptitude, I'm not an engineer, so I'll try not to overstate this.

From my perspective, there are two things to note abour the dams.

1. There appear to be no (what I would call) traditional spillways to allow water to flow safely overtop the dam; instead,

2. there are similar -- I don't know what the structures are called -- circular overflow "vents", clearly visible on the satellite images (they look like donuts from overhead) on the reservoir side of each dam. Once the reservoir water level reaches the top of these vents, it spills in to be directed through a tunnel/pipe to a point downstream of the dam. I have seen this sort of overflow/ vent mechanism in other dams, so it's not unique.

There appears to be no apparent (from the satellite images) secondary relief path for water -- aside from simply (catastrophic) cresting of the dam -- if the water flow into the reservoir exceeds the capacity of the vents for a sufficiently long time.

It also appears possible that there is limited to no active management of the dam overflow. Like the overflow on a sink or bathtub, once the water reaches the vent, it simply spills out.

Assuming the above basic info of the dams is correct, I've nonetheless not yet seen any description of what actually happened. Did the water crest the upstream dam, causing it to fail from the resulting erosion, sending a huge shock downstream to overwhelm the second dam, or did it fail structurally at a reservoir level that should have held, also resulting in a water surge downstream? Something else?

Is it safe to assume that the dams were designed with historical rainfall data taken into account? Was the storm that precipitated the failures simply way beyond anything before seen resulting in water flows beyond the designed capacity?

It's also instructive to be reminded of the Saguenay floods of 1996 (one can find remarkable news videos on YouTube). The rains in that event also overwhelmed the dams, and water flows exceeded spillway capacity. There was at least one dam of concern for possible failure, but they all held. In that event, Hydro Quebec also took heat for its water management before and during the event.

So, before scapegoats are rounded up and heads roll, let's understand what happened. It may simply be, once more, climate change and, notwithstanding the apparently dodgy maintenance, the dams may have met recognized engineering standards at the time of construction.

Many unanswered questions.

Just a note re the Google maps links: be sure to select the "satellite" view, otherwise you'll see just a blank image.

Gives rise to wonder about the new rainfall patterns, and the structural soundness of the Site C dam, with the geologicall foundation upon which it's being built being susceptible to shear forces. Apologies if I've butchered the grammar, translating the geology & physics into non-technical vocabulary. Not that I'd do any better rendering it into technical language!