Unprecedented flooding and the hidden role of coastal morphology in amplifying Mediterranean vulnerability during Cyclone Harry (19-22 January 2026)

Recent years have witnessed an increase in both the intensity of Mediterranean cyclones and the severity of associated coastal flooding. Between 19 and 22 January 2026, a powerful cyclone—designated cyclone Harry—caused extensive damage across several coastal states, including Algeria, Tunisia, the Balearic Islands, southern Italy, Malta, Greece, and Turkey. This event was characterized by atmospheric and marine anomalies that exceeded those observed in Mediterranean cyclones over recent decades, including the highest individual wave ever documented in the basin (approximately 16.6 m). This study presents a sensitivity analysis of flooding surfaces generated by storm waves from cyclone Harry across 17 selected areas of the central Mediterranean basin, aiming to understand how local morphological features modulated the coastal response. High-resolution digital terrain and surface models were constructed for each selected area using LiDAR and Terrestrial Laser Scanner data, integrated with nearshore bathymetric information from Multibeam surveys. These models were incorporated into the XBeach morphodynamic model to simulate wave propagation and consequent flooding. Model forcings included meteo-oceanographic variables from ERA5 and Copernicus reanalysis, tide gauge water levels, and buoy-measured significant wave heights. The results revealed flood extents unprecedented in past cyclone events over recent decades, with widespread impacts across the central Mediterranean. Crucially, the severity and spatial patterns of flooding were strongly controlled by local geomorphological features that acted as amplifiers of the hydrodynamic forcing. Offshore of coastal canyons (e.g., Lido Catanzaro, Calabria), increased seawater velocities produced nearshore water levels higher than those in adjacent non-canyon sectors. Elevated water columns and channelized flows along buried paleo-river alignments (e.g., Ognina, southeastern Sicily) enabled floodwaters to propagate inland up to 350 m, with velocities sufficient to cause structural damage. Urban morphology and infrastructure (e.g., Poetto in Sardinia and Valletta in Malta) further modified flood pathways, creating preferential zones of flow convergence. Along rocky coasts, widespread boulder displacements—including blocks transported onto buildings and infrastructure—attested to wave energy exceeding that of previous medicane and storm events. These findings underscore the necessity of incorporating high-resolution topographic and bathymetric data into coastal hazard assessments, as the local geomorphological setting fundamentally controls the transformation of regional-scale cyclone forcing into site-specific flood impacts. As Mediterranean cyclones intensify under climate change—with similar synoptic configurations now up to 15% windier than in the past—understanding these hidden morphological controls becomes essential for predicting vulnerability and designing effective adaptation strategies.