## 5 Discussion
In this context the flooding effect, linked to the SLR, may have a secondary effect on beach morphology and dynamics. In fact, the SLR will determine an adaptation in the coastal systems that could result in a redistribution of sediment with a shoreline retreat [38]. This effect along Sinis Peninsula could be less observable. [PERSON] et al. [55] showed different scenarios of flooding for western Sardinia. The mentioned authors estimated an increase in the sea level of 1.34 m at 2100 in respect to the present level for the worst scenario. The effect of SLR can be modulated by several factors, most of them of local origin, in fact, sandy beach responses to SLR are highly site-specific and temporally variable [63]. The beach and barrier can migrate inland in response to SLR with the roll over process when a sufficient accommodation space and a gentle slope beyond the beach and barrier characterize the area of migration [2; 31]. As recorded by MBES data, a series of cemented barriers are found in the inner shelf fronting the Mari Ermi beach between the depths of 21 m and 9 m (Figure 9a,b). [PERSON] et al. [31] identified analogous barriers in the Gulf of Oristano between the depths of 35 m and 15 m. For those barriers cementation is the primary process that allows their preservation and overstepping rather than a roll over. No cementation is found in the present barrier along Mari Ermi, consequently an increase in SLR can reduce the height of the top of the barrier, mainly in the southern sector (Figure 9b). The reduction in height above the mean sea level (MSL), in the worst scenario predicted by [PERSON] et al. [55], is about 1.34 m (Figure 9b). This could increase the overwash processes, which may cause an inward transfer of sediment. This process may promote a roll over process of the barrier as a consequence of the storms, as the level of the sea will increase. Is Arutas beach is enclosed by two headlands (Figures 1e and 9a,e,f), along this beach a rise in the sea level may increase the degree of embayment. In fact, the increase in MSL, as predicted by [PERSON] et al. [55], will not submerge the headland. Hence, SLR can result in a more pronounced beach rotation process in relation to the storms occurrences and direction. Accommodation space in the backbeach can allow migration inland of the berms crest and of the body of the beach (Figures 2a and 9a,c). However, human activities can be an impediment on the migration of the system towards the inland area. For the Mari Ermi and Is Arutas beaches, the effect of SLR on sediment redistribution may result in a shifting landward due to the roll over process. Maimoi beach can face the foreseeable SLR, in fact, this beach can be considered as a sediment-abundant beach (sensu [18]) due to the biogenic carbonate sediment provided by the coastal ecosystem to the Sinis Peninsula [35; 64]. In this context the SLR, as predicted by [PERSON] et al. [55], can cause migration landward of the shoreline and redistribution of sediment of the foredune with a retreat of the shoreline. The retreat could cause a more evident redistribution of sediment during storms, which may produce a lowering in beach level. Besides, the longshore movement of sediment will remain limited by the southern rocky headland, which does not allow a massive transfer of sediment towards the south. In this beach, the effect of SLR on sediment redistribution may result in a transfer of sediment from the dune towards the beach and the submerged area. This may partially reshape the beach profile with a potential shoreline retreat. This study confirms the importance of local factors, such as inherited geology, nature and availability of sediments. They can be relevant in the investigation of beaches responses to storms, and to develop a conceptual model on the adaptation of the beach and barrier system to the SLR.