Multiparameter analysis of the flood of November 15, 2017 in west Attica using satellite remote sensing

On November 15, 2017, a flash flood occurred after heavy rainfall in west Attica, affecting mainly the areas of Mandra and Nea Peramos. The tragic outcome is that 24 people lost their lives, and many infrastructures and assets were completely or partially destroyed. The FloodHub team of the Operational Unit “BEYOND Center for Earth Observation Research and Satellite Remote Sensing” of the Institute of Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS) of the National Observatory of Athens (NOA) was activated and studied the area, both by using satellite remote sensing and photo-interpretation and by visiting the area for data collection and more detailed analysis, including the identification of uncovered and covered parts of the streams and their former natural riverbank, as well as the identification of critical points, the examination of the adequacy of the cross-section of the streams and the engineering works, the taking of photographs, and the formulation of appropriate mitigation measures and the prevention of future failures and disasters. Among other things, the FloodHub team created an interactive web application and produced detailed maps depicting the updated hydrographic network, as it exists today following human interventions, the maximum extent of the flood (both mapped and simulated), as well as some of the critical factors that contributed to the massive disaster: arbitrary human interventions within the riverbank, the absence or inadequacy of technical works (flood protection and road drainage), and partly landscape changes on the one hand due to some small burnt areas upstream, and mainly due to urban expansion where building obstructs the flow of the streams. This multidisciplinary approach, with the combined use of satellite remote sensing and specialized data analysis and event simulation models, is a very useful service, which is available to the civil protection authorities and decision makers in support of their actions toward disaster resilience for the benefit of society as a whole.