Fast-track assessment of flash flood - erosion - landslide risks in fire-stricken river basins of the region of Attica, Greece

Abstract

The Region of Attica, the most densely populated region of Greece, which includes the capital, Athens, and contains critical infrastructures and social economic activities, was stricken by large forest fires in 2021 that caused incalculable damage. Thus, it was deemed necessary to conduct urgent assessment of flash flood-erosion-landslide risks in the small-sized fire-stricken river basins, with a view to prioritizing the required urgent interventions. For this purpose, the Operational Unit "BEYOND Centre of EO Research & Satellite Remote Sensing" of the Institute of Astronomy, Astrophysics, Space Applications & Remote Sensing (IAASARS) of the National Observatory of Athens (NOA), in cooperation with the Laboratory of Engineering Geology and Hydrogeology of the National Technical University of Athens (NTUA), studied the five river basins in the region of Attica that were affected the most by the aforementioned forest fires. Both research groups collected and studied all available geospatial data, and conducted extensive field visits in the areas of interest for on-site observation and collection of additional data, emphasizing at residential areas, road network and other critical infrastructures, and run hydrological, hydraulic, soil erosion and landslide models at high spatial resolution. All the collected and produced data, the flood hazard and landslide susceptibility maps, as well as the identified critical points and the proposed mitigation measures (both short-term and long-term) were delivered to the decision makers of the Prefecture of Attica and the 11 affected Municipalities, and access was given to the dedicated online platform which was specially developed for the needs of the authorities. Overall, 224 critical points were identified, 136 for flood and 88 for landslide risks. Presentations were organised for all the relevant stakeholders and the public. Subsequently, mitigation measures were applied to the most critical points by the Prefecture’s technical services. The methodology and the outputs of the project are in line with the requirements for the implementation of the EU Floods Directive 2007/60/EC, the Sendai Framework for Disaster Risk Reduction, the UN SDGs, as well as the GEO’s Societal Benefit Areas.