Assessing Coastal Flood Hazard and Damage from Cyclone Harry along the Calabrian Ionian Coast

Coastal flooding in urbanized Mediterranean areas is increasingly driven by compound meteo-marine events in which waves, storm surges, astronomical tides, and coastal exposure interact to generate severe impacts. This study reconstructs the causes, dynamics, and impacts of the coastal flooding that affected the Ionian coast of Calabria, southern Italy, during Cyclone Harry (19-22 January 2026). The analysis adopts a forensic hydrology perspective, combining multi-source documentary damage data with high-resolution atmospheric, oceanographic, and topographic datasets to identify the dominant physical drivers of the event and the most affected coastal sectors of the study area.

Cyclone Harry was first characterized at the Mediterranean scale using mean sea level pressure, 10 m wind fields, and wave spectral partitions. The storm developed from a rapidly intensifying low-pressure system over anomalously warm Mediterranean waters and generated severe south-easterly waves across the Ionian basin. Deep water meteo-marine conditions were then examined along approximately 250 km of the Ionian coast of Calabria at the 150 m isobath. An energy-based approach was applied to quantify the cumulative contributions of wind waves, primary swells, secondary swells, wind forcing, and static water-level variations. In addition, site-specific peak Total Water Level values along the emerged coastline were estimated by combining astronomical tide, inverse barometer effect, wind set-up, and wave run-up. Finally, multi-source documentary damage data were used to calculate a Damage Index (DI), which was compared with the Coastal Index (CI), a metric designed to identify the most critical littoral zones based on both hazard and exposure indicators.

Results show that wave action was the dominant forcing mechanism responsible for coastal flooding and infrastructure damage. Total wave energy reached values close to 3 × 10¹⁰ J/m in the southern sector of the study area and was mainly associated with primary swell, which contributed more than 70% of total wave energy along the entire coast and locally exceeded 90%. Static sea-level variations and wind setup played a secondary role, whereas wave run-up accounted for approximately 85-90% of peak Total Water Level in the damaged municipalities. Estimated peak Total Water Level ranged from 3.47 m to 5.03 m, with the most critical phase concentrated between late 20 January and early 21 January. Damage records indicate that 29 of the 50 coastal municipalities along the analyzed coastline reported impacts, especially to waterfronts, roads, seaside resorts, ports, utilities, and coastal buildings. Finally, the comparison between DI and CI highlights that the most critical littoral zones were severely hit by the cyclone Harry.

The integrated reconstruction highlights the importance of combining physical hazard modelling with documentary impact evidence to support emergency response, coastal planning, and climate adaptation strategies in highly exposed Mediterranean coastal regions.