## 5 Conclusions  
The methodological approach here presented to account for SLR and coastal land subsidence is transferable to other coastal zones and can be used to inform land planners and decisions makers that should take into account similar scenarios for a cognizant coastal management. The ongoing global climate change is affecting the inundation risks both through accelerating ice sheet melting (i.e., increasing the rate of eustatic SLR) and through more intense droughts, leading to unprecedented groundwater overexploiting and associated localized coastal land subsidence. Because climate change and SLR are posing unprecedented threats to the coastal environment, urbanization and population, multidisciplinary studies that include Earth Observations in combination with ground data and SLR projections will provide crucial information on the evolution of the coastal zones and their future expected shape. Our results have shown that the area underwent to coastal retreat up to 70 m in a few years only while diffuse land subsidence is locally exceeding 10 \(\pm\) 2.5 mm/year, due to compaction of artificial landfill, salt marshes and Holocene soft deposits. Given the ongoing land subsidence, the estimated high end of RSRR at 0.52 \(\pm\) 0.05 m and 1.52 \(\pm\) 0.13 m expected for 2050 AD and 2100 AD in the RCP 8.5 scenario, will lead up to about 10 km\({}^{2}\) of marine flooding. The inundation scenarios we have presented should be considered for a cognizant management of the coastal zone in response to the ongoing climate changes. \begin{table}
\begin{tabular}{c c c c c c} \hline
**A** & **B** & **C** & **D** & **E** & **F** \\ \hline \multirow{4}{*}{Sandy coasts} & VLM InSAR, & Coastal slope & Total shoreline & RSRR shoreline & \
\begin{tabular}{c} Residual shoreline \\ change (D–E) \\ (/year) \\ \end{tabular} &
\begin{tabular}{c} Residual shoreline \\ change (D–E) \\ (/year) \\ \end{tabular} \\ \multirow{4}{*}{Catania} & \(-8\pm 2.5\) & 6.7 & \(-4.78\) & \(-0.09\) & \(-4.69\) \\  & 9.45 & & \(-0.07\) & \(-4.71\) \\  & 0.7 & & \(-0.46\) & \(-3.55\) \\ \multirow{4}{*}{Siracusa} & \(-2\pm 2.5\) & 5.38 & \(-4.01\) & \(-0.06\) & \(-3.95\) \\  & 8.3 & & \(-0.04\) & \(-3.97\) \\  & 2.5 & & \(-0.17\) & \(-0.51\) \\ \multirow{4}{*}{Vendicari} & \(-4\pm 2.5\) & 3.3 & \(-0.68\) & \(-0.13\) & \(-0.55\) \\  & 10 & & \(-0.08\) & \(-0.6\) \\ \hline \end{tabular}
\end{table} 
Table 3: Shoreline changes for different slopes (column C) for three sandy coasts located at Catania, Siracusa and Vendciari (Column A). The difference between the total observed shoreline retreat (due to the sea-level rise, the increasing intensity of extreme marine events, VLM and deficit on the sediment supply in a coastal system—column D) and the retreat due to RSRR only (column E, geometric horizontal retreat), defines the residual shoreline change (D–E). The coastal erosion triggered by RSRR is the predominant effect in the shoreline change process for the analysed gentle sloping sandy coasts which are retreating at up to 4.78 m/year. Major consequences of inundation risk for the coastal areas of south-eastern Sicily include saltwater contamination of surface and underground waters, accelerated coastal erosion, wetland and saltmarshes losses and, in general, increased flooding. These effects are all related with the ongoing global warming and may lead to unprecedented socioeconomic impacts. Our analysis can improve flood resilience plans for an area of the Mediterranean with significant populations and infrastructures exposed to flood risk that can be exacerbated by storm surges, earthquakes, tsunamis and volcano-tectonic activity. The following are available online at [[https://www.mdpi.com/2072-429](https://www.mdpi.com/2072-429)]([https://www.mdpi.com/2072-429](https://www.mdpi.com/2072-429)) 2/13/6/1108/s1, SI-Supplementary Materials; Maps: S2-S12. Captions of Supplementary Materials: SI-Supplementary Materials. The description of the InSAR results validation. Maps S2.