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Derna dam collapses

Failure of two dams in Libya

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Background

Dam construction

The collapsed dams were built under Muammar Gaddafi's government by Yugoslav company Hidrotehnika-Hidroenergetika in the 1970s to control flooding, irrigate agricultural lands and provide water to nearby communities. They were described as clay-filled embankment dams with a height of 75 meters (Mansour dam) and 45 meters (Derna dam). The Derna (or Belad) dam) dam had a water storage capacity of 1.5 million cubic meters, while the Mansour (or Abu Mansour) dam upstream had a capacity of 22.5 million cubic meters.

Questions have been raised regarding the spillways of the dams in Derna; both operated using the 'Bell-mouth spillway' design.

Locations

  • Abu Mansour Dam – 32°39′34″N 22°34′38″E / 32.6594°N 22.5772°E
  • Derna (or Belad) Dam – 32°45′11″N 22°37′53″E / 32.75306°N 22.63139°E
  • Derna City – 32°45′49″N 22°38′10″E / 32.76361°N 22.63611°E

Political situation

The scale of the disaster in Derna was attributed to decades of neglect of the region by and following the rule of Muammar Gaddafi. Throughout the 2010s the city was a battleground, during the Libyan civil war, concurrent NATO intervention, and conflicts between rival governments established after Gaddafi's overthrow. After Gaddafi was overthrown, the city changed hands four times.

Warnings

Cracks had been reported in the dams as early as 1998. Derna's deputy mayor said that the dams had not been maintained since 2002 and were not built to withstand such volumes of water. According to a state-run audit agency, the lack of maintenance occurred despite the government's allocation of more than €2 million for that purpose in 2012 and 2013. However, a Turkish construction firm called Arsel Construction Company Limited claimed that it had been contracted to do maintenance work on the dam and build another one in 2007, and stated on its website that it completed that work in 2012.

As recently as 2022, a researcher at the Omar Al-Mukhtar University in Bayda, Libya had warned in a paper that the dams needed urgent attention, pointing out that there was "a high potential for flood risk". The paper also called officials to urgently carry out maintenance on the dams, prophetically stating that "(in) a huge flood, the results will be catastrophic". The Wadi Derna had been known to be prone to flooding, having experienced four major floods in 1942, 1959, 1968 and 1986.

Storm Daniel

Immediately before the dam failures, Storm Daniel caused extreme rainfall across northeastern Libya. Between 4 and 10 September 2023, the storm caused torrential rain in Greece and the Balkans, intensified into a Mediterranean cyclone, and moved south across the Mediterranean. On 10 September the storm made landfall in Libya near the city of Benghazi. Twenty-four-hour rainfall totals of 150–240 mm were recorded across northeastern Libya, and winds reached 70–80 mph. Daniel moved east and continued inland before degenerating into a low pressure-area, and the storm dissipated by 12 September.

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