Mapping expected sea-level inundation in the north-eastern coastal sector of the Island of Gozo (Malta, Mediterranean Sea)

According to the most recent scenarios, the global mean sea level is expected to keep rising during the next decades as a consequence of ongoing global warming. In this context, coastal areas are considered highly vulnerable to marine- and climate-related processes, such as coastal erosion and flooding. Such processes are expected to cause shoreline retreat and local morphological variations with consequent permanent inundation of low-lying coastal sectors. Understanding the evolution of coastal morphological features under changing climate conditions is therefore crucial to protect coastal natural ecosystems, infrastructure, and human activities against the influence of future sea-level rise. This work aimed at mapping expected medium- and long-term variations in the coastline position along the north-eastern sector of the Island of Gozo (Malta, central Mediterranean Sea) by considering sea-level projections for the years 2050 and 2100 under different climate scenarios. The study was based on high-resolution topographic data elaborated in GIS environment and derived from LiDAR data collected in 2013 by the Malta Environment and Planning Authority (ERDF, 2013). Sea level projections were downloaded from the NASA Sea Level Projection Tool, which provides the most updated global and local sea-level projections from 2020 to 2150 relative to the baseline period of 1995-2014 (IPCC, 2021). In addition, indicators available from the  Climate Data Store (CDS) Copernicus platform were also used to take in consideration the combined effect of permanent and temporary sea-level rise. Then, future coastline positions were defined by considering the areas with a topographic elevation lower than the future sea levels as prone to be permanently inundated by rising sea.

The analysis has allowed us to identify the bays of Ramla and Marsalforn as the most vulnerable areas since coastline changes expected in these zones will affect the economic, natural, and tourist activities present. In particular, in the case of Marsalforn, which is the main urban center in the study area, a wide range of utilities (roads, promenade, housing) will undergo increased coastal erosion/inundation threat, while coastline retreat due to sea-level rise is likely to have an impact on the dune system of Ramla Bay, which represents the best-preserved dune system in the Maltese Islands, and cause therefore loss in terms of natural ecosystems and related services. In order to provide stakeholders and planning authorities with a useful tool to support adaptation actions of the coastal communities threatened by sea-level rise induced by climate change, the results of the analysis are shown as easy-to-read maps in which areas at risk of permanent sea inundation are reported. Finally, this study lays the foundations for further research that will be aimed at providing a complete assessment of the marine- and climate-related processes (erosion, landslides, heavy rain, and fluvial flooding) impacting the coastal sectors of the Maltese Islands in a multi-risk perspective.