Ultra High-Resolution terrestrial and marine DEMs drive Relative Sea Level Rise projections and flooding scenario for 2100 A.D. for the Island of Panarea (Southern Tyrrhenian Sea, Italy)

Abstract

In the Aeolian Archipelago (southern Tyrrhenian Sea), Panarea Island and the islets of Bottaro, Lisca Bianca, Lisca Nera and Dattilo, is undergoing sea level rise, land subsidence, coastal erosion and beach retreat that are posing continuous threats to coastal stability and infrastructures built along the coastal zone. With the aim to assess the coastal changes by the end of 2100 according to the IPCC climatic scenarios, that predict a global sea level rise even more than 1 m, a detailed evaluation of the potential coastal flooding has been estimated in the frame of the PANDCOAST project, funded by the INGV.This work focuses on the use of Unmanned Aerial Vehicles (UAVs) imagery combined with multibeam bathymetry data collected in different years for the generation of the very  high-resolution Digital Terrain and Marine Model (DTMM) of the Panarea Island and its archipelago. Scenarios are based on the determination of the current coastline position, high resolution Digital Terrain and Marine Models, vertical land movements and climatic projections.  The data fusion of detailed topographic data, up to 2 cm/pixel for the subaerial sector with sea level rise projections released by the Intergovernmental Panel on Climate Change (IPCC) for the SSP2.6 and SSP5 climatic scenarios for this area, are used to map the expected multi-temporal sea level rise scenarios for 2050 and 2100.In the analysis have been incorporated the effects of the vertical land movements (VLM) as estimated by the Global Navigation Satellite System (GNSS) network located in the archipelago. Assuming constant rates of VLM for the next 80 years, relative sea level rise projections provide values between 31±11 cm by 2050 and 104±27 cm by 2100 for the IPCC AR6 SSP8.5 scenarios and at 27±10 cm by 2050 and 73±24 cm by 2100, for the IPCC AR6 SSP2.6 scenario, with small variations in the individual islets of the archipelago. With these scenarios, the lowest elevated coasts of the islands are exposed to increasing marine flooding, especially during storm surges and high water levels particularly heavy from the north-western sectors.