Why was the Libya flooding so deadly? Weak infrastructure, rough geography

The combination of extreme weather, vulnerable geography, and weak dams and roads made the deluge the worst North Africa has seen in almost a century.

Libya’s National Center of Meteorology reported a record 24-hour rainfall of 414.1 millimeters — more than 16 inches — in Bayda from Sunday to Monday, according to the World Meteorological Organization. Most of the rain fell in just six hours, according to weather historian Maximiliano Herrera. Bayda only receives about half an inch in a typical September and about 21.4 inches of rain in an average year. Scientists say climate change has made heavy rainfall events more common in recent years.

About 170 millimeters of rain — nearly 7 inches — fell in Al Abraq in the Derna district, according to Floodlist, a website that aggregates flood information. Witnesses told Reuters that the floodwaters in Derna reached as high as 10 feet. Other locations received 150 to 240 millimeters (6 to 9 inches) of rain. The storm also brought strong winds up to 80 kph (50 mph).

The torrential rain and wind were produced by Storm Daniel, which caused deadly flooding in Spain and record-breaking heat over large parts of Western Europe.

After it triggered catastrophic flooding in Greece, Turkey and Bulgaria last week that killed at least 26 people, according to the Associated Press, Daniel transitioned into what is known as a “medicane,” or tropical-like cyclone that occasionally forms over the Mediterranean Sea. The storm became stronger as it drew energy from the abnormally warm waters, before drifting to the south and unloading excessive rainfall over northeastern Libya, where rain flowing down the mountainous terrain overwhelmed dams.

Medicanes, short for Mediterranean hurricanes, feature clouds spiraling around a cloud-free eye similar to tropical cyclones, but they are typically smaller, have weaker winds and don’t last as long. Research has shown that medicanes are likely to become stronger in a warming world, although they may occur less frequently.

Having lost much of its energy over the arid terrain of Libya, the storm’s rainfall intensity eased as it moved into northern Egypt, where its remnant winds were kicking up a dust storm.

The eastern city of Derna appears to be the most severely affected by the floods. Photos and videos showed homes and fields submerged. The city is located at the end of a valley known as the Wadi Derna. Wadis are types of valleys that are dry except during the rainy season. Torrents of water tore through the dams, sweeping entire buildings into the sea.

The port city, which has an estimated 90,000 residents, is low-lying, making it more susceptible to flooding. The soil, dry and cracked after a long, hot summer, is not equipped to absorb such large amounts of water.

The city is controlled by Gen. Khalifa Hifter, head of a coalition of factions and irregular fighters in the east known as the Libyan National Army (LNA).

“Derna was a city that was formerly held by Islamic extremists,” said Natasha Hall, a senior fellow at the Center for Strategic and International Studies who focuses on humanitarian emergencies in the Middle East. “This was an area that was the marginalized of the marginalized of the conflict.”

Two rivers flow into Derna, which is supposed to be protected by two dams. Both collapsed as water overwhelmed them.

The flooding is unusual for the region — one of the last times floods this deadly hit North Africa was in 1927 in Algeria. Roads and bridges are not built to be resilient to these kinds of disasters.

Hall also noted that authorities didn’t properly communicate with people about the dangers.

“Typically, you have a robust early-warning system in place to be able to warn citizens to evacuate or take cover,” she said. “We didn’t have that in this situation.”