Storm Daniel flooding aftermath in Libya: drivers, implications, and the need for a rapid assessment system

Abstract The dire aftermath of Mediterranean Storm Daniel, which hit the coastal city of Derna in Libya in the fall of 2023, resulted in the most devastating floods in Africa over the last century, with a human toll exceeding 11,300. The Derna disaster is an omen of the alarming vulnerability of arid urban areas to intensifying hydroclimatic extremes that remain poorly quantified. In flood-impacted areas, the absence of rapid damage assessment systems compromises rescues and relief efforts, which are best carried out within the first 48 hours. To address those deficiencies, we identified the hydroclimatic and anthropogenic drivers that exacerbated Derna’s flood impacts and developed a rapid and reliable CNN-based system that can be operate locally with limited satellite imagery to assess post-flood urban damage. Our results indicate that 4302 buildings and 26.55 km of roads have been affected by the catastrophic floods. The building and road counts deduced from our rapid assessment system are validated by published reports from global agencies, showing a strong match. We demonstrate that, in urban arid areas such as Derna, anthropogenic drivers override natural ones in determining the magnitudes of storm-induced flood impacts. We provide near- and long-term recommendations to increase the resilience of coastal cities to the growing risks of hydroclimatic extremes, given inefficient urban planning and inadequate observational resources for monitoring natural hazards in most arid areas.