Risk register · entry
Q2 · The CoconutDerna dam collapses
Two neglected dams burst overnight after explicit published warnings.
The rare, high-impact event that was always coming, and was always going to be called unforeseeable afterwards.
Why this room
The mechanism itself was binary and easy to model (a dam holds or bursts), but decades of dormant, unpriced probability met a genuine tail event, a 1-in-300-to-600-year storm intensified by warming, producing an outcome wildly disproportionate to how "simple" the underlying risk looked on paper.
The record
- Abu Mansour dam: 75m high, 22.5 million cubic meter capacity; Derna dam: 45m high, 1.5 million cubic meter capacitylikely
- Dams built in the 1970s by Yugoslav firm Hidrotehnika-Hidroenergetikalikely
- No maintenance since 2002; cracks documented since 1998; earlier vulnerabilities flagged in 1986likely
- ~2 million euro maintenance contract (2012-13), reportedly marked complete by Turkish contractor without verified workuncertain
- 2022 Sebha University study by Abdelwanees Ashoor rated Wadi Derna basin 'high risk' for floodingcertain
- Storm Daniel struck Libya September 10, 2023, after forming September 4-10certain
- Rainfall event assessed as 1-in-300 to 1-in-600-year magnitude, made ~50x more likely and up to 50% more intense by human-caused warming (World Weather Attribution)likely
- Dams collapsed at approximately 2:40am and 2:50am on 11 September 2023; official capacity warning issued at 2:59amlikely
- ~30 million cubic meters of water releasedlikely
- Official death/missing toll: ~4,352 to 8,900 depending on source and date; unofficial estimates 11,000-24,000uncertain
- More than 40,000 people displacedlikely
- 12 officials sentenced in July 2024 for negligence in dam maintenance and water managementlikely
Sources
The book
This entry is one of 111 in the register. The full story, and what it cost the people who lived it, is in Risky Business by Claudia Zeisberger, David Munro and Joanna Reijgersberg-Siew.
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