## 5 Discussion and Conclusions  
Our radar survey showed that the analyzed sites experienced beach progradation that was not continuous but punctuated by the formation of berms. Other radar features point out a process of dune development starting from the formation of a berm during stormy weather that, due to return to fair weather along with the abundance of sediment supply, became inactive because it was no longer reached by the (storm) wave run-up. In the context of strand-plain progradation, the increase in distance between the beach face (foreshore) and the location of the storm berm prevents the aggradation of beds on the seaward side, and the overtopping of sedimentation onto the ridge and washover phenomena. Currently, the berm detached from the marine processes. The morphology of the relict storm berm, even if forming a low relief, interferes with the wind dynamics and can become the embryonic core of a wind-formed coastal dune. In this sense, the elevation of a coastal dune can correlate with the rate of coastline progradation. A low rate of progradation allows the supply and activity of frontal dunes and their growth over time. This seems to be the case for the southern sector, where the elevation reached by the frontal dune, although affected by strong ongoing erosion processes, is up to 5-6 m (Figures 6 and 7a-d). This model, which has long been used, especially for sandy-gravel beaches ([3,11] and references therein), can also be used for sandy coasts such as the one examined, even if the inclinations and thicknesses of the beds have to be reconsidered according to the grain size and storm intensity. We consider a positive sedimentary balance with a high rate of sedimentary supply to be the major reason for the increasing separation between the beach face and the berm. In the northern sectors, GPR results show that a wind-dominated phase followed the beach progradation phase. The strand-plain progradation was not a continuous process because erosive events (radar surface, i.e., erosional unconformities) interrupted the constructional processes. These erosive events can be related to temporary reductions of sedimentary nonurishment or related to high-energy events such as storms. However, net strand-plain  
Figure 6: Processed (**a**,**b**,**c**,**d**,**e**) and corresponding interpreted (**a**\({}_{\textbf{1}}\)**,**b**\({}_{\textbf{1}}\),**c**\({}_{\textbf{1}}\),**d**\({}_{\textbf{1}}\),**e**\({}_{\textbf{1}}\)) GPR profiles. For profiles location see Figure 2.  
progradation occurs because the rate of sedimentation on the beach's face prevails over periods of either no deposition or coastal erosion. In the last 60 m of the profiles (from the beach face inland), the northmost sector (Figures 2a and 6) shows a large area constituted by an incipient dune with pioneer vegetation passing to a backshore. The extension of the area and the scarce development and growth of a frontal dune system are indicative of a high rate of progradation, as confirmed by several studies regarding the analysis of historical coastline locations ([33] and references therein). Conversely, a different morphodynamic framework characterizes the southern sector. There, strong erosional processes (Figure 7a,b), mainly due to the significant decrement in sediment supply [42], have taken place since the last century [34]. The distance between the foreshore and the base of the frontal dune is very short (~10 m, Figure 7a,b), and therefore, the seaward flank is affected by the wave run-up. The wave run-up has a destructive effect on the berm-dune system by creating erosional unconformities. These data collectively show how the imaging of a strand-plain subsurface through a GPR survey can provide relevant elements supporting hypotheses on the temporal and spatial evolution of depositional settings. Therefore, the radar features may highlight the roles of the sedimentary budget in directly controlling the construction/destruction of backshore landforms and indirectly controlling the construction of a dune system [57; 58].