## 6 Conclusions  
The RST-FLOOD, a well-established satellite-based approach for flood detection and monitoring, has been fully implemented here for the first time with SNPP-VIIRS data. The event that affected the Metaponto Plain (southern Italy) during the first week of December 2013 has been investigated using such an approach by analysing 171 SNPP orbits, for a total of 684 VIIRS SDR products. A study aimed at identifying the best signal, among the opportunities assured by the first three VIIRS Imagery bands, has been preliminarily performed identifying the NDSI (I1 - I3/I1 + I3) as the metric with the best trade-off between reliability and sensitivity respect to the investigated event features. Such a signal has been then implemented within the RST-FLOOD approach, through the computation of the ALICE index aimed to investigate the flood dynamics in the 4-8 December 2013 period. The achieved findings demonstrated the good potential of the proposed approach in providing daily reliable indication on the flooding event. Only a residual 11.5% of possible false positives was recorded when the whole investigated scene was considered, reducing to only 4% when the area mostly affected by the event was investigated. An anomalous area of about 18 km\({}^{2}\), flooded \"for sure\" accordingly to the outcomes provided by previous works [31; 37] as well as of the flood documentations [32; 33; 34; 35; 36], was detected by RST-FLOOD outside the flood hazard map, suggesting the need of its updating for better managing future risk, especially considering that an increase in intensity and in frequency of extreme meteo-hydrological events has expect in the next year for the Basilicata region [65]. The comparison with another VIIRS-based method [11], developed to work a global scale, confirmed the reliability of the outputs, suggesting a good capability of RST-FLOOD in detecting flooded area. Finally, the achieved results demonstrated the potential of medium-resolution optical sensors, like VIIRS, in detecting floods that affect small watersheds, usually investigable only by using data (optical- or microwave-based) at higher spatial resolution [17]. Considering the high temporal resolution offered by VIIRS sensor (that thanks to the recent launch of JPSS-1 has further improved), the relevance of the achieved results become quite evident. The possibility of having continuous and reliable indication about the flood localization and extent may represent a valuable resource for both decision makers and hydrological models. Their assimilation would allow both for an updating of the model set up conditions as well as for a general quality improvement of the results. Finally, their integration with high spatial resolution optical data, such as those acquired by the MultiSpectral Instrument (MSI) aboard European Space Agency (ESA) Sentinel-2 mission, will allow for a more detailed view of the areas affected by the event. Conceptualization, T.L. and M.F. ; Data curation, T.L., E.C., M.F. and V.S. ; Formal analysis, T.L., E.C., M.F. and V.S. ; Investigation, T.L. and M.F. ; Methodology, T.L., M.F., N.P. and V.T. ; Validation, M.F. ; Visualization, T.L. ; Writing--original draft, T.L. and M.F. ; Writing--review & editing, N.P. and V.T.. This work has been partly funded in the framework of the MIUR SMART BASILICATA project. We would like to acknowledge the Civil Protection of the Basilicata Region for providing river water level data. The authors declare no conflict of interest. * Munich (2017) Munich, R.E. Topics Geo--Natural Catastrophes 2017. Analyses, Assessments, Positions. 2018.