As the number of victims of the devastating floods in Libya rises day by day, questions about human responsibility for the collapse of the dams are mounting.
Two dams in the town of Derna collapsed on Sunday as storm Daniel swept through the area, sending people, entire buildings and neighborhoods into the sea.
Foreign experts say that the huge number of victims, whose bodies are thrown into the sea every day, is the result of the bursting of the dams, which were built in the 1970s by the former Yugoslav company Hidrotehnika, which still operates in Belgrade.
Serbian experts who worked on the construction of dams in Libya in those years, however, believe that the quality should not be questioned, and that the collapse was due to inadequate maintenance.
"I absolutely claim that all of us who worked in Libya, project supervision over the construction of dams, were responsible, knowledgeable, moral people.
"We didn't allow ourselves any 'fluffing'. Those dams fell for other reasons, not because they weren't done well," says Predrag Buca Đorđević, who worked as a geological engineer on the construction of the Wadi Kam dam in Libya, for the BBC in Serbian.
Until the publication of the text, the BBC was unable to get a comment from the current director of Hidrotehnika Radovan Draškić.
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Two dams in Derna, one 12 kilometers from the city and the other closer, only a few kilometers away, gave way under the huge amount of rainfall brought by storm Daniel.
According to Libyan meteorologists and hydro experts, the amount of rain that fell on the area around Derna in the east of the country in 24 hours is equal to the amount of precipitation for the entire month of September.
The dam in the construction of which Đorđević participated, about 70 kilometers from Tripoli, was built approximately at the same time as those in Derna, in the period when Yugoslav companies were internationally recognized.
"Yugoslav companies were known in the world for their high quality of construction, from Energoprojekt and Hidrotehnika (Serbia), through Energoinvest (Sarajevo) and Elektroprojekt (Croatia).
"The standards for building such dams at that time were excellent," says Professor Dragan Savić, an expert in hydraulic engineering in Great Britain, who teaches at the University of Exeter, for the BBC in Serbian.
Until the publication of the text, the BBC was unable to get a comment from the current director of Hidrotehnika Radovan Draškić.
- Once upon a time there was a city in Libya... it was called Derna
- 'The sea keeps throwing up bodies': Death toll in Libya floods feared to be up to 20.000
- What is the danger of floods in Serbia and how to protect yourself
- How to restore life and dry the house after a flood, the fourth time in seven years
Two dams in Derna, one 12 kilometers from the city and the other closer, only a few kilometers away, gave way under the huge amount of rainfall brought by storm Daniel.
According to Libyan meteorologists and hydro experts, the amount of rain that fell on the area around Derna in the east of the country in 24 hours is equal to the amount of precipitation for the entire month of September.
The dam in the construction of which Đorđević participated, about 70 kilometers from Tripoli, was built approximately at the same time as those in Derna, in the period when Yugoslav companies were internationally recognized.
"Yugoslav companies were known in the world for their high quality of construction, from Energoprojekt and Hidrotehnika (Serbia), through Energoinvest (Sarajevo) and Elektroprojekt (Croatia).
"The standards for building such dams at that time were excellent," says Professor Dragan Savić, an expert in hydraulic engineering in Great Britain, who teaches at the University of Exeter, for the BBC in Serbian.
Maintenance of dams
The dams in Derna were earthen dams.
Predrag Đorđević explains that concrete dams were not built in Libya due to the nature of the terrain itself.
"Earth dams are built on terrains where there is no rock mass on the side or the rock mass is of poor quality to receive concrete," says Đorđević.
Dragan Savić adds that when an earthen dam is well designed and regularly maintained, then there should be no problems.
"These dams worked well, because in 1986 and 2011 they did the job and saved the city from floods.
"Don't forget that they did the job for about 50 years," says Savić.
The earthen dams in Derna were built by Hidrotehnika, on whose website you can read that the two dams had an accumulation of 1.5 and 18 million cubic meters.
Water management experts told the BBC that it is likely that the first dam, about 12 kilometers from the city, collapsed first, causing water to slide down the river valley towards the second dam, located closer to Derna - where entire settlements were flooded.
Local authorities estimate that the final number of victims could be up to 20.000.
The World Health Organization appealed to the Libyan authorities not to bury the victims in mass graves.
More than 1.000 people have been buried in mass graves so far, the UN estimated.
Eyewitnesses said that heavy rains from Storm Daniel caused floodwaters to flow through the streets of Derna.
But around 2.30am on Sunday, they heard an explosion at the Great Dam and the flood turned into a huge torrent in less than an hour.
Dragan Savić reminds that the average annual precipitation in this area is about 270 mm, and some sources claim that storm Danijel brought 200 mm in a very short period of time.
"That can only mean that what the dam was designed for, especially its spillway, was insufficient to receive this enormous amount of water.
"Such dams must not overflow over the body of the dam, because such a large amount of water carries away the downstream layer of rock and disrupts the impermeability of the entire dam and its clay core, thereby collapsing the stability," explains the professor.
Predrag Đorđević states that at every dam there must be teams that take care of maintenance, and that the question is whether this was the case in Libya.
In a research paper published last year, hydrologist Abdelvanes AR Ashor from the Libyan University Omar Al-Mukhtar, indicated that the repeated flooding of the seasonal river bed would be a threat to Derna.
He cited five floods since 1942 and called for immediate steps to ensure regular maintenance of the dams.
"If a major flood occurs, the result will be catastrophic for the city's residents," he warned.
However, Ahmed al-Masmari, the spokesman for the self-proclaimed Libyan National Army (LNA), which governs eastern Libya, expressed a different view in a statement to the BBC Arabic service.
"What happened was beyond the capacity of the dams that were built to withstand certain water levels in the region, taking into account the amount of rain that falls.
"We do not know for sure whether the dams were regularly maintained. But I guess, from what I've personally seen, that even if the dams were newer or well maintained, they wouldn't be able to handle that amount of rainfall, especially in Derna."
In addition to the two dams, Hidrotehnika has also built several facilities in this area for the irrigation of agricultural areas and the water supply of the city and surrounding settlements, according to the company's website.
Hidrotehnika also built the Wadi Gatra dam system, which, as stated, should contain the flood wave that occurs in the rainy season and endangers the city of Benghazi, and which should serve to irrigate the land and reduce the salinity of underground water.
Yugoslavs in Libya
Hidrotehnika was founded in 1946, and its first major business was the Zvornik hydroelectric power plant.
During the following years, it built about 60 dams and hydroelectric power plants in the country and the world, among them Đerdap and Bajina Bašta in Serbia.
The company has also worked on projects across Africa.
"Hydrotehnika was the most important contractor company in Yugoslavia," says Đorđević.
He explains that workers and engineers from Serbia also went to Libya.
Unlike workers, engineers moved with their families.
He recalls that then the Energoprojekt engineers got a five-story building for themselves.
"The children played all day together. We work, and in the evening when we come back on the terrace we have parties, we also had contests for Miss and Mister.
"It was a very nice period of our lives when we had time to be together as a family," says 85-year-old Djordjevic, who went to Libya with his wife and two-year-old son in 1972.
He says the major infrastructure projects across Libya were Gaddafi's initiative.
"He gave people sheep, land, and guaranteed monthly incomes," adds Đorđević.
Colonel Muammar al-Gaddafi was killed in 2011, after which the country was divided into two parts governed by opposing governments.
In Tripoli, there is a government recognized by the international community and led by Abdulhamid al-Dbeiba, while in Tobruk, some 1.000 kilometers from Tripoli, the government of Osama Hamad is in power, which governs the part of the country most affected by floods.
But immediately after the disaster, the government in Tripoli started to help the affected areas.
However, some analysts believe that the political chaos in what was once Africa's richest country has led to poor infrastructure maintenance and is now hampering rescue efforts.
Watch the video about Libya and the death of Gaddafi:
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