## 2 The Test Case  
The selected Region of Interest (ROI) is the Metaponto plain area, located between the south-eastern corner of the Basilicata Region (southern Italy) and a subset of the Puglia Region (Figure 1). This plain is of particular socio-economic and environmental importance for the region and interested by degradation processes mainly linked to land management and soil characteristics [24,25]. The area encloses the terminal sector of all the main Basilicata river basins, namely Sinni, Agri, Cavone, Basento and Bradano and of the Lato River, the major one of the Puglia Region (Figure 1). All these rivers are strongly seasonal dependent, with maximum hydrometric levels recorded in winter and minimum in the summer [26]. The annual minimum flow rate of the Sinni and Agri rivers, whose basins are those mostly affected by precipitations at regional level, is 1.38 and 0.5 m\({}^{3}\)/s, respectively [27]. Lower values are instead recorded for the Bradano and Basento rivers (i.e., 0.04 and 0.08 m\({}^{3}\)/s), while Cavone River flow rate is practically nil [27]. The river levels are registered by the Civil Protection Department of Basilicata Region [28], by means of the five gauging stations (depicted by yellow dots in Figure 1) positioned close to the river mouths (i.e., within the Metaponto Plain), at the intersection with the freeway of the Basilicata region called \"StradaStatale 106.\" Based on the temporal range when water levels were available (January 2011-September 2016), the three maxima measured at the five gauging stations and the corresponding dates are reported in Table 1, where they are listed from the highest to the lowest. Looking at the data in Table 1 it is worth noting an evident increase in the water level of all the rivers during the first week of December 2013 (Figure 2), which suggests the occurrence of an extreme hydrological event. The \"Ciclone Nettuno\" storm hit the Basilicata Region between 30 November and 3 December 2013, producing heavy convective precipitation [29; 30]. A daily precipitation value of 130 mm was recorded on 1 December at the Bradano River gauging station, with a cumulative \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Sinni** & **Agri** & **Cavone** & **Basento** & **Bradano** \\ \hline \multirow{4}{*}{Max River Level Date} & 3.59 m & 4.19 m & 5.22 m & 7.92 m & 6.04 m \\  & 01/12/2013 & 01/12/2013 & 04/02/2014 & 02/12/2013 & 02/03/2011 \\ \cline{2-5}  & 3.47 m & 3.93 m & 5.00 m & 7.81 m & 5.39 m \\ \cline{1-1} \cline{2-5}  & 28/03/2015 & 13/03/2016 & 02/12/2013 & 03/12/2013 & 02/12/2013 \\ \cline{1-1} \cline{2-5}  & 3.46 m & 3.55 m & 4.81 m & 7.60 m & 4.83 m \\ \cline{1-1}  & 23/02/2012 & 02/12/2013 & 19/02/2011 & 02/03/2011 & 03/12/2013 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The three maximum water levels (listed in decreasing order) measured in the period 01/01/2011-30/09/2016 and the corresponding dates for the Sinni, Agri, Cavone, Basento and Bradano rivers [28]. Note that for Agri River, data are available only for the period 01/01/2013-30/09/2016. Figure 1: Localization of the Region of Interest (red box, in WGS-84 lat-long projection). In background the RGB False Colour (Red = Shortwave Infrared, namely I3 VIIRS band; Green = Near Infrared, namely I2 VIIRS band; Blue = RED, namely II VIIRS band) of VIIRS Imagery data acquired on 4 December 2013 at 12.10 GMT. Yellow dots indicate the localization of gauging stations along the five main rivers reaching the Ionian coast. The red segment and the white box will be used in the text. one of 200 mm for the entire event [31], indicating the strong intensity of this meteorological event. The consequent flooding event affected not only the Metaponto Plain in the Basilicata Region but also some areas in Puglia, where the Lato River overflowed near Castellaneta Marina, causing the closure of the freeway \"Strada Statale 106\" and severe damage to the surrounding lands and villages [28; 32; 33; 34; 35; 36].