A systematic assessment of the effects of extreme flash floods on transportation infrastructure and circulation: The example of the 2017 Mandra flood

Flash floods are one of the most catastrophic natural hazards in many areas of the world, inducing significant losses on a yearly basis. Transportation and its infrastructure remain particularly vulnerable to such events despite their crucial role in many socioeconomic activities and commuter safety. Despite the adverse climate change projections, there is limited research providing a holistic and quantified overview of the impact of rare, extreme flash floods on the transportation of affected areas both in terms of infrastructure and circulation. The research team surveyed the effects of an extreme flash flood at Mandra, Greece, aiming to provide a systematic overview of the extent and typology of its impacts on transportation. The study quantifies the effects on different elements of transportation infrastructure, as well as vehicle circulation disturbances using floating car data. Results show an extensive impact with approximately 40% of the mad network inundated or inaccessible and over 80% of river crossings (bridges, fords, and culverts) suffering damages, debris deposition and/or flooding, while critical cross-sections of the drainage network were diminished. Circulation was affected heavily with significant vehicle speed drops, travel times and distances increasing in and around the affected area. The findings indicate a considerably higher degree of impacts in comparison with less rare flash floods, implying that transportation systems may require extensive adaptation to address the increase of extreme events' frequency induced by climate change.