The First Relative Sea Level Rise and Storm Surges Scenarios up to 2150 CE for the Coasts of Monterosso and Vernazza, Cinque Terre National Park (Liguria, Italy)

Abstract

The UNESCO World Heritage coastal zone of Cinque Terre (Liguria, northern Italy) is increasingly threatened by ongoing sea-level rise. To assess expected sea levels up to 2150 CE under the IPCC Sixth Assessment Report (AR6), we carried out a first evaluation of potential coastal flooding for Monterosso and Vernazza under different Shared Socioeconomic Pathways (SSPs), integrating high-resolution topography and bathymetry, geodetic data, historical tide-gauge evidence, and storm-surge modeling. The historical sea-level analysis indicates a non-stationary rising trend for the Ligurian sector. Relative sea-level rise (RSLR) projections were computed for SSP1-2.6, SSP3-7.0 and SSP5-8.5, including local land subsidence, and were used to map the potential inundated areas for 2030, 2050, 2100, and 2150 CE. In 2150, projected RSLR is expected to range from 0.60 m to 1.17 m, corresponding to flooded surfaces of 9931 m2 and 22,079 m2 in the SSP1-2.6 and SSP5-8.5 scenarios, respectively. Because site-specific long-term run-up observations are not available for formal calibration at the two study sites, the storm-surge simulations are interpreted as scenario-based hazard envelopes. Even within this framework, storm surges with return times of 1 and 100 years in the SSP5-8.5 scenario cause maximum wave run-up in the range of 5.12 m and 13.36 m. The results show that narrow pocket beaches and low-elevation harbor areas are the most critical receptors and that adaptation measures should focus on quay elevation, drainage/backwater management, and the protection of transport and tourism infrastructures.