## 5 Discussion
The horizontal displacements were mitigated by some stabilization measures implemented during 2007-2009 at the dam structure, which resulted in a moderate reduction of movement measured at BM208 (i.e., at the starter dam) of about one-third of the previously observed rate of displacement (Table 2). The time series of displacement of BM208, from 1982 to 2014, achieved by benchmark time series [1], has been extended to 2018 (Figure 9), using the A-DInSAR measurements. The time series since the second half of the 90s until 2011 shows a steady growth of the eastward movement, with a constant velocity. From 2011 to 2014, and therefore until the end of the period analyzed by [PERSON] [1] (orange line in Figure 9), the curve reaches a plateau, and the horizontal displacement slows down. From 2015 to 2019, the A-DInSAR analysis shows instead that the cumulative displacement values of the eastern dam begin to slightly grow again (blue line in Figure 9) at the BM208. It is worth mentioning that the time series of the displacement of BM208 represents the behavior of the base of the dam structure (starter dam), while at higher altitudes of the dam, the intensity of horizontal displacements is considerably greater, as stated above (Figure 7b,d). As discussed in previous works, the geodetic and the inclinometer data show that the starter dam and the foundation soil above the shallower shear plane in clays \begin{table}
\begin{tabular}{c c c} \hline \hline
**Horizontal Velocity of** & **Year** & **Data Source** \\
**BM-208 (mm/yr)** & & \\ \hline  
\hline \end{tabular}
\end{table} 
Table 2: Horizontal surface displacement rates of benchmark BM-208 located in the easter sector of the dam; the velocity is an averaged value for each analyzed year. Figure 9: Time series of horizontal surface displacements of benchmarks BM-208; orange line: benchmark time series from [1]; blue line: A-DInSAR time series. (45 m asl) move as a single, rigid body [1]. This behavior changes at higher elevations within the dam, where there is a more complex deformation mechanism. The longitudinal section along the eastern dam (Section 1 in Figure 6a,b) shows how cumulative displacement is distributed along the eastern perimeter and allows for the analysis of the spatial deformation pattern of the east side of the dam. Each curve of the graph shows the cumulative deformation that affected the dam up to September of each year. This timing was chosen in order to compare and combine this graph with the same longitudinal section of Jamiolkowski [1], which represents a plan view of horizontal cumulated displacements from 2004 to 2013. The latter has been extended with the measurements obtained by A-DInSAR for the years 2014-2018, along the longitudinal section at medium height of the dam (Figure 10). Despite some uncertainties about the exact location of the section of Jamiolkowski, the curves show a very similar trend: greater displacements occur in the central part of the eastern dam, and the rates of eastward displacement (that can be deduced by the distance between the curves) are similar. Two remarks can be made about the above mentioned discussion: the first one is that in the eastern sector of the TSF, the dam does not behave like a rigid body and shows areas of greater weakness in the central part; the second remark is that, although the horizontal deformation seems to have had a slowdown from 2010 to 2013, it continued in 2014 to 2018 with recovered intensity, up to almost 370 mm of displacement. It is possible that stabilization and prevention works performed to reduce the lateral sliding of the dam have not been effective. In the western sector of the dam (which was not described by [PERSON] [1]), the deformation rates are very similar to that of the eastern dam, apart from the direction of the horizontal movement, which is to the west, and the spatial pattern of the displacement along the longitudinal section (Figure 6e), which shows a displacement in bloc of the dam body.