| Dam safety
account for more than 50% of that. With the long-term average sitting around 60Mm3
year to year, Wishart said
it is a highly variable system that had implications when looking at the underlying issues associated with failure. One of key determining factors contributing to the
disaster itself was the design of the structures’ morning glory spillway that reaches saturation fairly quickly. In the immediate aftermath there was concern across Libya about the potential for more dam failures upstream of a number of other important cities. To help understand this, initial risk assessments were remotely carried out and an additional 14 dams were identified, bringing the portfolio total to about 28. There were two very high risk dams with 27,000 people at risk, five high risk with around 25,000 people, two medium to high, one medium, one medium to low, and one low risk dam. Wishart wanted to highlight the challenges associated with ensuring the safety of dams and downstream communities, especially in the context of operation and maintenance, in what are known as Fragile and Conflict Affected States such as Libya. He spoke about similar situations in other FCA countries, such as Sudan, which are facing significant challenges in governance, security, and development, with specific concerns in terms of both financial and human resources availability. According to Wishart, there were also other “events
playing out in Libya” when it was recognised there was a need for an independent and more objective assessment of the failure. This proved to be “both timely and very important” when 12 officials were detained in the immediate aftermath of the failure in July 2024 and sentenced up to 27 years in prison. According to news reports some of these officials, who were responsible for managing water resources and maintaining the dams, were charged with crimes including negligence, premeditated murder and wasting public money.
Detailed assessment According to ICOLD Vice President Laurent Mouvet,
the experience of the Abu Mansour and Derna dams
underscore the need to identify national priorities for safeguarding the rest of the national Libyan dam portfolio, mitigating the potential impacts of further dam failures on infrastructure, public health and environment. Eight specific actions were proposed following the findings of expert assessment, a comprehensive review of existing literature, and good international industry practices pertaining to measures that can improve safety of dams and downstream communities. These were: 1) Carry out more detailed assessment of the 2023 flood event. There was a relatively high level of uncertainty regarding spatial and temporal distribution of Storm Daniel’s rainfall through the Wadi Dam catchment area, demonstrating difficulty in accurately characterising the return period of the flood event.
2) Carry out more detailed assessment of dam failures. 3) Improve flood forecasting, early warning systems and emergency preparedness.
4) Determine level of protection for Derna City. 5) Determine appropriate interventions for building back better using climate resilient principles.
6) Develop a regulatory framework for dam safety assurance.
7) Launch a national dam safety programme. 8) Implement stakeholder engagement and communications plan.
Above: Derna in Libya after the dam collapse © seraj.elhouni /
Shutterstock.com
Below: Widespread damage across Derna © seraj.elhouni /
Shutterstock.com
Lessons learned
Was the catastrophic flooding in Derna, Libya - one of the deadliest hydrometeorological disasters on record - an inevitable outcome of rare weather conditions, or did the design of the infrastructure fail to account for probable risks? This is the question Moshe Armon et al ask in their research published in Science Advances. By using a combination of atmospheric re-analysis, satellite data, and hydrologic modelling, they claim to have overcome key limitations typical of data-scarce, high-variability regions and revealed that despite the catastrophic impact, the return periods of the rainfall and flood were only a few decades. Hydraulic simulations revealed that the dam failures amplified the damage nearly 20-fold compared to a dam-free scenario. With extensive and timely implications, they say their findings underscore the importance of uncertainty-aware risk assessment and highlight the value of distributed flood prevention and early warning systems in mitigating risks in vulnerable regions. The authors go on to add that the Derna disaster should serve as an alarming sign that frequency analyses of extreme events in drylands should take into account the very high natural climate variability, the different and evolving approaches to derive extreme
value estimates, changes in land use and runoff coefficients, and climate change impacts. “These challenges,” they claim, “cast doubt on the economic and the environmental rationale for dam construction as a strategy to mitigate flood risks in drylands.” The lessons from Derna are not confined to this region and similar risks are present globally, requiring immediate attention from both the scientific community and policymakers. “Our results strongly imply that the complete failure of other dams is not a matter of if, but rather when,” Moshe Armon et al add. “We urge the scientific community, local knowledge holders, and authorities to collaborate on this timely hazard to improve knowledge, data availability, and risk communication and to re- evaluate the planning of habitat areas along dryland streams to prevent the next disaster.”
Reference
Anatomy of a foreseeable disaster: Lessons from the 2023 dam-breaching flood in Derna, Libya. Moshe Armon, Yuval Shmilovitz and Elad Dente. Science Advances. 28 Mar 2025. Vol 11, Issue 13.
www.science.org/ doi/10.1126/
sciadv.adu2865
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