SafeThessaloniki 2022 Proceedings | ISSN 2654-1823 SafeThessaloniki 2022 – 9th International Conference on Civil Protection & New Technologies 29 September-1 October, ‘Nikolaos Germanos’ Conference Center, Thessaloniki | www.safethessaloniki.com - www.safethessaloniki.gr | safethessaloniki@safegreece.org TOWARDS AN OPERATIONAL FORECAST MODEL FOR COASTAL INUNDATION DUE TO STORM SURGES: APPLICATION DURING IANOS MEDICANE Christos Makris 1 , Yannis Androulidakis 1 , Zisis Mallios 1 , Vasilis Baltikas 1 , Yannis Krestenitis 1 1 Division of Hydraulics and Environmental Engineering, Department of Civil Engineering, Aristotle University of Thessaloniki, Greece (E-mails: cmakris@civil.auth.gr, iandroul@civil.auth.gr, zmallios@civil.auth.gr, vmpaltik@civil.auth.gr, ynkrest@civil.auth.gr) ABSTRACT This paper presents the application of a numerical model (CoastFLOOD) for the simulation of coastal inundation due to storm surges enhanced by tides. The implementation is based on output of sea level elevation caused by the combined action of storm surges and astronomical tides from operational forecasts with High Resolution Storm Surge (HiReSS) model in the Mediterranean Sea. The presented case study of coastal inundation refers to the littoral floodplain of Livadi coastal inlet at the island of Cephalonia (central Ionian Sea, western Greece), induced by the passage of Ianos Medicane (with Category 2 Hurricane characteristics) in September of 2020. Validation of storm-induced sea level elevation against in situ data by tide gauges is also presented in tandem with estimations of flooded areas over coastal lowlands. The latter are compared with satellite observations (Sentinel-2 images) producing the Normalized Difference Water Index (NDWI). The seawater run-up extended up to several hundreds of meters inland, depending on hydraulic connectivity between lowland areas, which determined the inundation extents during the storm surge events. Keywords: coastal inundation, storm surge, Ianos Medicane, operational forecast, numerical modelling 1. INTRODUCTION The Mediterranean Sea is considered to be a hotspot in reference to impacts of extreme weather events on the coastal zone. Intense storm surge events might threaten lowland coastal areas mainly by inundation effects on littoral floodplains which may cause human casualties, land loss, damages to onshore infrastructure and properties, environmental degradation, etc. Therefore, in the present work, a new coastal inundation module (CoastFLOOD) [1] is implemented in operational forecast/hindcast modes coupled to a tidally enhanced storm surge model (HiReSS) [2] for the proper simulation of large scale storm-induced coastal flooding. The Ianos Medicane [3] case study is investigated in terms of invoked coastal inundation on the littorals of coastal inlets at the island of Cephalonia (central Ionian Sea, western Greece). For this, numerical, in situ, satellite, and GIS land elevation data are combined. 2. METHODOLOGY Extremely deep atmospheric depressions in the synoptic scale on the Mediterranean basin usually lead to the formation of storm surges on the coastal boundary in local scale, due to two main mechanisms: i) the inverse barometer effect underneath the low-pressure area of the cyclone, and ii) the wind-induced accumulation of seawater masses towards the coast. 2.1. Available Data (Atmospheric Input, GIS Land Elevation, Field and Satellite Observations) Ianos Medicane, with characteristics similar to a Category 2 hurricane (wind gusts of 160 km/h), propagated over the central Mediterranean in mid-September 2020 [3] and induced damages on both page 69