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Article | WTW Research Network Newsletter

Storm Daniel: A cautionary tale on the need to maintain infrastructure before it’s too late

By Neil Gunn | April 15, 2024

Storms are not constrained by national boundaries, and as they demonstrate their relentless force, they often leave a lasting mark on the regions they traverse.
Climate
Climate Risk and Resilience

In September 2023, torrential rain from Storm Daniel put overwhelming pressure on the Derna dams, making their eventual catastrophic collapse inevitable.

Meteorological history

The storm began as a low-pressure system in the Black Sea on September 4 and tracked inland across the Balkan Peninsula, bringing unprecedented rainfall, particularly in Greece’s Thessaly region on September 5 to 6, as well as Bulgaria and Turkey. The system then traversed the warm Mediterranean Sea, where due to favorable weather and sea conditions, it transitioned into a medicane — a portmanteau of “Mediterranean” and “hurricane”. The medicane made landfall in Benghazi, Libya, on September 10, with tropical storm force winds of 70 to 80 kilometers per hour, and record-breaking rainfall (Figure 1).

Image taken from NASA's Terra satellite showing Storm Daniel as it made landfall in Libya on 10 September 2023.
Figure 1: Natural-color image, acquired with MODIS on NASA’s Terra satellite, shows Storm Daniel on September 10, 2023, as it made landfall in northeastern Libya.

Source : NASA

Storm Daniel's development was aided by an “Omega blocking” pattern. This meteorological phenomenon occurs when a high-pressure system is flanked by two low-pressure systems, creating a configuration that resembles the Greek letter omega (Ω ). Such a setup typically disrupts the usual west-to-east progression of weather systems. In Daniel's case, this Omega block effectively anchored the storm, providing conditions conducive to its development. The storm’s intensification was also fueled by unusually high sea surface temperatures in the Mediterranean Sea.

Unprecedented rainfall in Greece

Storm Daniel brought exceptional rainfall to Greece (Figure 2) with Zagora in Thessaly receiving 1,092 millimeters in under 24 hours, a staggering 138% of the average annual rainfall for this region.

Photo of flooding in Karditsa, Greece on 8 September 2023
Figure 2 : Flooding in Karditsa, Greece, September 8, 2023.

Source : Alamy

The extreme weather significantly disrupted transportation, damaging major routes across Greece. Agricultural losses were considerable; 750 square kilometers of farmland flooded and more than 200,000 livestock perished, leading to problems with waterborne diseases.

Greek Prime Minister Kyriakos Mitsotakis estimated direct economic damages at €2.5 billion (US $2.8 billion), while academics projected a broader economic impact of up to €5 billion (US $5.6 billion).[4] According to the Hellenic Association of Insurance Companies (HAIC), insurance claims are expected to be around €400 million (US $440 million), marking Greece's largest payout for flood and storm damages since HAIC's records began in 1993 — but far below the estimated economic loss. This reflects a substantial protection gap, which is unsurprising as Greece's insurance penetration stands at just 2.4% of GDP, well below the European Union average of 7.5%.

Storm Daniel struck Greece a few weeks after the country grappled with devastating wildfires. In response to these consecutive natural disasters, the Greek Prime Minister proposed tax breaks for individuals purchasing insurance. Additionally, the government is actively considering mandating natural catastrophe insurance coverage in the future.[5]

Disaster in Derna

Despite a state of emergency being declared in Libya before the storm's landfall, the fractured nature of the country led to a breakdown in the transmission and messaging of warnings.

The storm made landfall near Benghazi on September 10; the most destructive aspect was its heavy rainfall. While the totals were lower than those in Greece, large areas of the country saw record-breaking precipitation. Al Bayda accumulated 414 millimeters over 24 hours, 76% of the annual average.[6] However, while heavy rainfall ravaged the region, the true tragedy unfolded in Derna. Here residents were told to avoid the beach and advised to shelter at home, presumably in case of a storm surge.[7]

Two aging dams constructed in the 1970s played a critical role in the catastrophe. The structures had been built in a steep-sided canyon, the Wadi Derna. They were designed to supply water and help reduce the incidence of flooding.[8] As well as highlighting maintenance issues, a 2022 report suggested that the designers may have underestimated the potential discharge from the catchment that could be generated during extreme events.[9],[10] In the early hours of September 11, catastrophic failure occurred and the upper dam collapsed, unleashing a torrent that overwhelmed the 75-meter-tall lower dam, situated only 100 meters upstream of the nearest houses.A quarter of Derna, built on the Wadi's historic delta, was obliterated (Figure 3).

Photo of damage caused by collapse of Derna dams in Libya.
Figure 3. Damage following the collapse of the Derna dams in Libya.

Source : Alamy

Rescue efforts faced delays due to storm damage and security concerns, leaving at least 4,300 confirmed dead and 8,000 to 10,000 still missing.[11],[12] Economic damages in Libya are projected to be several billion U.S. dollars. When combined with the losses in Greece, Storm Daniel will far exceed the previous record for a Mediterranean storm set by Tropical Storm Rolf in 2011, which inflicted approximately $2 billion in damages (in 2023 U.S. dollars).

The tragedy exposes glaring vulnerabilities. Unreliable governance during the Gaddafi era was compounded by conflict in the years following his death. Together these hampered both preventive measures and emergency response. Poor communication and an incomplete understanding of the storm's potential led to inadequate warnings, leaving some residents vulnerable in flood-prone areas.

The storm's impact on infrastructure, including the closure of the port and damage to roads, impeded the initiation of recovery efforts, including aid delivery. Even months after the storm, over 40,000 remain internally displaced within Libya. [12] International aid organizations such as the Red Cross are actively working to provide support for 200,000 people affected by the disaster.

Lessons for the future

Natural disasters are often exacerbated by human actions, and the tale of Derna is more poignant because it was a disaster waiting to happen. This is what can happen when a society is complacent and doesn’t heed warnings. Societies are dependent on engineered infrastructure, which requires inspection and maintenance, but a significant proportion of global infrastructure is operating at or beyond its design life. Governance challenges vary across nations, with some facing additional strains from conflict as is the case in Libya. Many governments have also made difficult choices over expenditure since the 2007 – 2008 banking crisis and the 2019 – 2020 global pandemic. When these issues intersect with natural hazards that exceed the design criteria of structures, which is becoming increasingly likely due to climate change, there may be more tough times ahead. But there is also an opportunity to avert future disasters, contingent on our willingness to acknowledge and act upon these warnings.

The Mediterranean region was severely impacted by Storm Daniel, an intense weather system that unleashed unprecedented rainfall and resulted in significant flooding across Bulgaria, Greece, Turkey and Libya. With economic damages estimated at multiple billion U.S. dollars and at least 4,300 fatalities, it is both the costliest and the deadliest Mediterranean storm in recorded history.

References

  1. Flaounas, E. et al. Mediterranean cyclones: current knowledge and open questions on dynamics, prediction, climatology and impacts. Weather Clim. Dyn. 3, 173–208 (2022). Return to article
  2. Ali, E. et al. Cross-Chapter Paper 4: Mediterranean Region. In: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press.(2022). Return to article
  3. González‐Alemán, et al. Potential increase in hazard from Mediterranean hurricane activity with global warming. Geophys. Res. Lett. 46, 1754–1764 (2019). Return to article
  4. BBC News. Storm Daniel: Greek farmers fear they may never recover. (2023). Return to article
  5. France 24. Greek PM vows for a restart after criticism for natural disasters' handling. (2023) Return to article
  6. World Meteorological Organization. Storm Daniel leads to extreme rain and floods in Mediterranean, heavy loss of life in Libya. (2023). Return to article
  7. PBS. Experts had long warned ‘consequences will be disastrous’ if dams in Libya ignored. (2023). Return to article
  8. Hidrotehnika. Wadi Derna 1973-1977.(2023). Return to article
  9. Ashoor, A. A. R. Estimation of the surface runoff depth of Wadi Derna Basin by integrating the geographic information systems and Soil Conservation Service (SCS-CN) model. JOPAS 21, 90–100 (2022). Return to article
  10. Al Jazerra. Libya floods: Conflicting death tolls, Greek aid workers die in crash. (2023) Return to article
  11. Rigodanza, G. and Lashi, F. Satellite view: Understanding the impact of Storm Daniel. (2023). Return to article
  12. United Nations Office for the Coordination of Humanitarian Affairs. Libya Flooding: Situation Report #11. (2023) Return to article
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