## 4 Discussion  
InSAR LOS displacement measurements enable quantitatively analyzing the deformation processes along the Italian coastlines in the last decades, over small-to-large areas, and for short-to-long temporal spans. Moreover, these measurements can identify areas affected by intense ground deformation phenomena that can be strongly exposed to coastal erosion, inundation, and flooding events. The availability of multi-temporal InSAR data represents valid support to improve the knowledge of both slow and fast ground deformation phenomena, ensuring a synoptic view of the whole Italian coasts. In this work, we showed several ground deformation phenomena detected by X and C-band InSAR data along the Italian coastline due to the complex interplay of natural and anthropogenic activities. In detail, the Ravenna coastline and Po Plain were affected by land subsidence related to natural soil compaction and consolidation, as well as groundwater pumping activities and gas/oil extraction from on-shore and offshore wells. The subsidence observed near Rome, in the area surrounding the Tiber River and Fiumicino town, are induced by soil compaction effects that are mostly present close the rivers due to soft alluvial sediments. Particularly compelling is the case of the \"Leonardo da Vinci\" airport, where a transition between the natural sediments, ranging from clay levels to medium-to-coarse sand, leads to a deformation gradient observed along runway three. Moving to the south of Italy, we observed a different phenomenon in the Campi Flegrei area, west of Napoli city. This area is affected mainly by the bradyseism phenomenon, i.e., the succession of several inflation/deflation phases because of the presence of a nested volcanic district. Here, we showed, by InSAR analysis, the significant uplifting phase that occurred in the time interval 2011-2015 due to the magma recharging in the magma chamber of the central volcano of the area, e.g., the Solfatara of Pozzuoli. Going further south, we observed non-negligible ground deformation along the Sibari Plain, along with the Ionic Coast of the Calabria region, due to groundwater overexploitation at nearby nautical centers, residential centers, and industrial zones. Looking at the southernmost Calabrian coastlines and the Sicily region, the soil compaction of sediments due to groundwater exploitation represents the primary cause for the observed coastal ground deformation, which was also observed in the case of Augusta Bay along the eastern coast of Sicily. Concerning the Puglia coastline, we analyzed the Taranto gulf, detecting no evidence of significant deformation phenomena, despite the massive presence of anthropogenic industrial activities. These case studies show how InSAR-based analysis enables observing ongoing deformation phenomena along the Italian coastline, and not only well-constrained, subsiding, and uplifting signals. InSAR retrievals, i.e., deformation rate maps, and time series can be appropriately coupled with sea level rise measurements, marine observations, and atmospheric modeling to forecast the future levels of sea rise, coastal erosion, and flooding, thus estimating the effects of the ongoing climate changes on coastal areas. To these purposes, the scientific community is moving toward designing an InSAR-based semi-automatic procedure for performing a near real-time coastline surveillance service. It is worth noting that the test cases shown here were studied by X and C-band SAR data provided by the CSK (still active) and ENVISAT (inactive from 2010) missions. The main problem of such missions is the satellite revisit time of about 16/35 days, which prevents a near real-time updating of the results.