## 4 Results and Discussion
### Shoreline Evolution (Past and Future)  
Table 2 shows the rates of coastline change for the three periods analyzed (1930-1989; 1997-2022; and 1930-2022) in the three areas (A, B and C) that have or have had shorelines. In zone A, between 1930 and 1989, the erosion is important, with an average rate in the zone of 1.13 m/yr (Figure 4). As can be seen in Figure 5, most of this erosion is due to the period 1930-1956. Even in transect 1, the 1977 shoreline was ahead of the 1956 shoreline, reflecting a small accretion in the area, probably due to the construction of the small grain on the south side of the river mouth. It seems evident that in this area, there was some erosion near the natural mouth of the Segura River before it was channeled. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Period 1930–1989**} & \multicolumn{4}{c}{**Period 1997–2022**} & \multicolumn{4}{c}{**Period 1930–2022**} \\ \hline
**ZONE** & **TRANSECT** & **NSM** & **LRR** & **LCI** & **LRR** & **NSM** & **LRR** & **LCI** & **LRR** & **NSM** & **LRR** & **LCI** & **LR2** \\  & & **(m)** & **(m/yr)** & **(m/yr)** & **(m/yr)** & **(m/yr)** & **(  
In the northern area of zone B, near the breakwater (transects 4-8, Table 2 and Figure 6), the erosion during the period 1930-1989 is significant, with an average of 0.89 m/yr. It is worth remembering that between 1990 and 1992, the beach was regrown by about 50 m due to the creation of the marina [4]. As shown in Figure 4, this material added to the beach eroded rapidly, as the 1997 shoreline was behind the 1989 one. However, for the period 1997-2022, the values shot up to an average of 1.29 m/yr. It seems more than evident that the construction of the breakwater and the channelization of the river has accelerated a natural process (Figure 4). From transects 9 to 13, erosion rates only reach 0.36 m/yr for the period 1930-1989. This indicates that this zone, already farther from the mouth of the river, was less affected by the natural shoreline erosion. In contrast, after construction works in the area, the rate skyrockets to 1.22 m/yr, almost one meter more in a much shorter period of only 25 years. The erosion data for the area between transects 14 and 17 present a low LR2 for the first epoch analyzed. This is because the shorelines in this area are very  
Figure 4: The upper graph shows the NSM of all transects in zones A, B and C in the periods 1930-1989 and 1997–2022. The lower graph shows the LRR values of each transect for the same zones and periods. Figure 5: (**a**) Shorelines and transects 1 to 3 from 1930 to 1989 (background image from 1989). (**b**) Image from 2022 of the same area. close together, having accretion and erosion epochs, which makes it difficult to fit the linear regression [48]. In any case, the net movement of shoreline erosion in these transects was 5 m for the 60-year period (1930-1989). However, for the period 1997-2022, the mean NSM for these transects is 31.71 m, which seems to confirm the increase in erosion south of the breakwater. Looking at the entire period of 92 years, the mean erosion of all transects in zone B is 0.92 \(\pm\) 0.24 m/yr. It happens that throughout zone B, erosion rates have increased after anthropic actions, reflecting their negative effects, especially in the southern part (Figure 4). In zone C, for the period 1930-1989, something similar to zone B occurs with some of the linear regression, where the LR2 value is low. In this zone, some of the transects show a net accretion for this period (see Figures 4 and 7a). Erosion at Babilonia Beach was very small until 1989, with only 8.72 m in 60 years, whereas in the last 25 years, 12.09 m, about 40% more, eroded in less than half the time. This has caused the loss of beaches in front of houses and, therefore, has left them directly exposed to sea waves (see Figure 2).