Rising Waters, Falling Dams: Deciphering the Derna Flood Disaster

Abstract On September 11, 2023, the city of Derna along the Libyan coast experienced an unprecedented disaster as Storm Daniel unleashed heavy rainfall, leading to the failure of dams and catastrophic flooding. The study investigates the dynamics of this event, exploring the factors leading to dam failure and their role in the devastating flooding of Derna. Through hydrologic, hydraulic, and geotechnical modeling, the research investigates scenarios with and without dams to understand the specific impact of dam failure on flood inundation. The storm's origin, the rainfall distribution in the Wadi Derna watershed, and the subsequent runoff and reservoir filling are analyzed. The study reveals that the dams, if survived would have been minimally effective in controlling the flash flood in the city due to the extreme nature of Storm Daniel's runoff. However, the surge wave generated due to their failure had a devastating impact on human lives and infrastructures. The findings emphasize the critical need for thorough hydro-meteorological assessments and flood management practices in regions vulnerable to climate change impacts and recommend a shift from over-reliance on structural flood control measures. The analysis also highlights the 'dam paradox' and the importance of effective communication, evacuation plans, and comprehensive flood control evaluations in mitigating the impact of extreme storms.