CNN –
It started with a bang at 3 a.m. Monday when residents of Derna were sleeping. One dam burst, then a second, sending a huge wave of water pouring through the mountains toward the Libyan coastal city, killing thousands as entire neighborhoods were washed into the sea.
At least 5,000 people have been killed in Libya by this week’s floods, Doctors Without Borders (Médecins sans frontières) said in a statement on Thursday, revising an earlier estimate.
The eastern Libyan city of Derna, the epicenter of the disaster, had a population of around 100,000 before the tragedy. According to the authorities, at least 10,000 people are still missing. CNN could not independently verify the numbers.
According to the International Committee of the Red Cross (ICRC), buildings, houses and infrastructure were “obliterated” when a seven-meter wave hit the city. The International Committee of the Red Cross (ICRC) announced on Thursday that bodies were now washing up on the banks again.
With thousands killed and many more still missing, the question is why the storm, which also hit Greece and other countries, caused so much greater devastation in Libya.
Experts say that in addition to the powerful storm itself, Libya’s disaster was significantly worsened by a deadly confluence of factors including aging, crumbling infrastructure, inadequate warnings and the impact of the worsening climate crisis.
Check out this interactive content on CNN.com
The extreme rains that hit Libya on Sunday were caused by a system called Storm Daniel.
After hitting Greece, Turkey and Bulgaria with severe flooding that killed more than 20 people, it became a “drug” over the Mediterranean – a relatively rare type of storm with similar characteristics to hurricanes and typhoons.
The drug strengthened as it crossed the unusually warm waters of the Mediterranean before torrential rain fell on Libya on Sunday.
It brought more than 16 inches (414 mm) of rainfall in 24 hours to Al-Bayda, a town west of Derna, a new record.
Although it is still too early to definitively attribute the storm to the climate crisis, scientists are confident that climate change is increasing the intensity of extreme weather events such as storms. Warmer oceans provide the fuel for storms to form, and a warmer atmosphere can retain more moisture, leading to more extreme precipitation.
Storms “are becoming more severe due to climate change,” said Hannah Cloke, a professor of hydrology at the University of Reading in the United Kingdom.
Derna is prone to flooding and its dams have caused at least five deadly floods since 1942, the last of which was in 2011, according to a research report published last year by Libya’s Sebha University.
The two dams that burst on Monday were built around half a century ago, between 1973 and 1977, by a Yugoslavian construction company. The Derna Dam is 75 meters (246 feet) high and has a storage capacity of 18 million cubic meters (4.76 billion gallons). The second dam, Mansour, is 45 meters (148 feet) high and has a capacity of 1.5 million cubic meters (396 million gallons).
These dams have not been maintained since 2002, the city’s deputy mayor Ahmed Madroud told Al Jazeera.
But the problems with the dams were known. The Sebha University newspaper warned that the dams in Derna had a “high flood risk potential” and that regular maintenance was needed to avoid “catastrophic” flooding.
Check out this interactive content on CNN.com
“The current situation in the Wadi Derna reservoir requires immediate action by authorities for regular maintenance of existing dams,” the paper recommended last year. “Because in the event of a major flood, the outcome would be catastrophic for the residents of the valley and the city.” It was also noted that the area lacked sufficient vegetation to prevent soil erosion. Residents in the area should be made aware of the dangers of flooding, it said.
Liz Stephens, a professor of climate risk and resilience at the University of Reading in the United Kingdom, told CNN that serious questions were being asked about the dam’s design standard and whether the risk of very extreme rainfall had been adequately taken into account.
“It is very clear that without this dam failure we would not have experienced the tragic death toll it caused,” she said.
“The dams would have initially held back the water, and their failure might have released all the water at once,” Stephens also told the Science Media Center, adding that “debris trapped in the floodwaters would have added to the destructive force.”
Derna has been badly damaged in the past, its infrastructure upended by years of fighting.
After the battle against ISIS and later against eastern commander Khalifa Haftar and his Libyan National Army (LNA), the city’s infrastructure has collapsed and is woefully inadequate in the face of floods like that caused by Storm Daniel.
With better warnings, most of the casualties in Derna could have been avoided, said the head of the United Nations World Meteorological Organization, Petteri Taalas.
“If there had been a normally functioning weather service, they would have issued the warnings and also the emergency management would have been able to evacuate people and we would have avoided most of the human casualties,” Taalas told reporters at a press conference on Thursday.
Talaas added that political instability in the country has hampered WMO’s efforts to work with the Libyan government to improve these systems.
But even robust early warning systems are no guarantee that all lives can be saved, said Cloke.
Dam failures are very difficult to predict and are quick and severe, she told CNN. “This tremendous amount of water is destroying the entire city,” Cloke said. “It is one of the worst floods ever.”
While dams are typically designed to withstand relatively extreme events, this is often not enough, Cloke said. “We should prepare for unexpected events, and then you add climate change to the mix, and that magnifies these unexpected events.”
The risk that climate-related extreme weather poses to infrastructure – not just dams, but everything from buildings to water supplies – is a global risk. “We are not prepared for the extreme events that are coming,” Cloke said.