Libya's flash floods kill more than 5,300 people

Poor infrastructure and low-lying locations have left eastern Libyan cities suffering heavy damage as floodwaters from Storm Daniel surged down from the mountains to the west.

Storm Daniel devastated Greece last week, swept across the Mediterranean, and then made landfall on the northeastern coast of Libya on September 10, affecting a number of cities including Benghazi, Bayda, and Derna. These areas suffered record rainfall on September 10-11 due to the storm.

Heavy rains caused two dams on the upper reaches of the river that runs through the city of Derna to burst, sending torrents of water rushing into the city, sweeping away everything, collapsing homes, and killing more than 5,300 people, according to local officials.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) estimates that at least 5,000 people are missing, while local officials say about 10,000 are still unaccounted for, possibly swept out to sea or buried in the rubble. Abdulmenam al-Ghaithi, the mayor of Derna, warned on September 13 that the death toll could be as high as 18,000 or 20,000.

Experts say extreme weather, vulnerable geography, and flimsy dams and infrastructure have made the Libya flash floods the deadliest disaster in North Africa in nearly a century.

Extreme weather and vulnerable geography

The Libyan National Meteorological Center recorded a record 414.1 mm of rain in 24 hours from September 10 to 11 in Bayda, 100 km west of Derna, according to the World Meteorological Organization (WMO). Most of the rain fell in the mountainous areas of western Libya within six hours, said weather expert Maximiliano Herrera.

Total rainfall over three days up to September 11 in areas of Libya. Graphic: WP — Total rainfall over three days as of September 11 in northeastern Libya. Graphic: *WP/NASA*

Bayda received just 12.7 mm of rain in September, compared to an annual average of more than 543.5 mm. Scientists say climate change has made heavy rains more frequent in the region in recent years.

The town of Al Abraq, between Bayda and Derna, recorded 170 mm of rain, according to the flood monitoring website Floodlist. Other places received 150-240 mm.

These areas are all located upstream, where the terrain is high, causing floodwaters to accumulate and rush towards the eastern coastal area, where the city of Derna with about 90,000 people is located.

Derna lies close to the coast and is low-lying compared to the rest of the area, making it prone to flooding. The land is dry and hard after a long, hot summer, so rainwater tends to stay on the surface rather than soak into the ground.

This is considered one of the factors that create flash floods with fast moving speed. Wetter areas often have loose soil, which helps absorb most of the rainwater and reduce the risk of flooding.

The location of two dams that broke, causing heavy damage to the city of Derna. Graphics: WP

Witnesses described floodwaters in the city of Derna as high as 3 metres, with houses and fields submerged. Derna lies at the end of a valley known as Wadi Derna. "Wadi" is used in some Arab countries to refer to a valley or channel that is always dry, except during the rainy season.

Infrastructure

Floods are rare in North Africa. The last time the region experienced a flood was in 1927 in Algeria. As a result, infrastructure is often not built to handle this type of disaster.

The situation is even worse in Libya, a North African country that has been engulfed in war for more than a decade, with factions vying for power. The eastern region, where the city of Derna is located, is controlled by an opposition coalition that is not recognized by the international community, making aid efforts and communications around the disaster zone even more difficult.

“Derna was once controlled by radical Islamists,” said Natasha Hall, a researcher on humanitarian emergencies in the Middle East at the Center for Strategic and International Studies (CSIS).

The city is currently under the control of General Khalifa Hifter, leader of the Libyan National Army (LNA) alliance, following fighting in 2018-2019. Libya’s infrastructure has generally been weakened by the prolonged conflict, and structures in Derna have not been fully repaired or rebuilt due to the conflict.

“Dams, desalination facilities, power grids and roads in Libya are all in disrepair,” said Stephanie T. Williams, the UN secretary-general’s special adviser on Libya for 2021-2022.

Derna has two rivers running through it, and is protected by two dams built in the 1970s to prevent flooding. However, because the area rarely floods, the dams were built rather crudely, with a core of clay and reinforced with boulders and crushed stone on both sides.

As a result, when the volume of water pouring in from the western mountains was too great, both dams quickly eroded and broke, sending about 30 million cubic meters of water pouring into Derna. Derna’s deputy mayor Ahmed Madroud said the city’s most densely populated area was right in the path of the flash floodwaters flowing into the sea.

Williams notes that Derna also sits at the foot of a steep mountain range. It is the top of an area called an alluvial fan, which is formed by sediment carried by rivers and streams. During heavy rains, these alluvial fan areas are at risk of sudden, powerful flash floods that can sweep away everything in their path.

"At least 20% of the city was destroyed in the floods," said Madroud.

Ms Hall noted that local authorities also failed to warn residents of the danger when heavy rains occurred. "Normally, we would have an early warning system to tell people to evacuate or take shelter if necessary. But in this case, there was no such thing," she said.