**5. Conclusions**

In this paper, new *ED* thresholds for Slovenia were calculated using the automatic tool proposed by Melillo et al. [32] The main objective was to reconstruct the cumulated event rainfall and the duration of the rainfall conditions responsible for landslide occurrences in order to obtain reliable thresholds that could be implemented in a LEWS. Based on the presented results the following conclusions can be drawn.

The proposed *ED* thresholds were determined for the entire Slovenian territory, given that the current national landslide prediction system provides alerts at a national scale. Compared to other thresholds obtained with empirical approaches, the current curves are slightly lower. It should be noted, however, that the threshold used for the comparison is at 5% NEP. The main strength of the frequentist approach lies in the possibility of calculating thresholds at different non-exceeding probabilities, which could be used in probabilistic schemes to produce rising alert levels for landslide occurrence [17].

Thresholds for different MAR classes were also calculated. Due to the high relative uncertainties of the threshold parameters, not all the calculated thresholds can currently be implemented in a LEWS. However, they provide an idea of the landslide triggering conditions in the study area. The higher the mean annual rainfall in an area, the more rainfall is needed to trigger a landslide.

Thresholds for different geological classes were also determined. Due to the high relative uncertainties, not all the defined thresholds are reliable enough to be implemented in a LEWS. They can be considered only as an indicator of the rainfall conditions responsible for landslide occurrences in different lithological units. The sedimentary rocks are more subject to weathering and thus have the lowest thresholds and are by far more susceptible to landslide occurrences than those areas with limestone and magmatic bedrocks.

The main advantages of the tool—whose code is freely downloadable at http: //geomorphology.irpi.cnr.it/tools/rainfall-events-and-landslides-thresholds/ctrl-t-algorithm/ctrlcode/ctrl\_t\_code.r/view—are (i) the fast processing of a large amount of data, which provides results in a short time, (ii) the reduction of subjectivity in the whole process of reconstructing rainfall conditions responsible for the failures and (iii) the definition and validation of rainfall thresholds.

The proposed 15% NEP threshold might be further tested using the national prototype LEWS and critically assessed on the basis of case studies, reviewing the landslide database and ensuring accurate information on the location and the occurrence date/time of the landslide.

**Author Contributions:** Conceptualization, G.J., S.L.G., M.M. and M.J.A.; Data curation, G.J. and M.J.A.; Formal analysis, G.J., S.L.G., M.M. and M.J.A.; Methodology, S.L.G., M.M., S.P. and M.T.B.; Software, S.L.G., M.M., S.P. and M.T.B.; Visualization, G.J., S.L.G., M.M. and S.P.; Writing—original draft, G.J., S.L.G., M.M., S.P. and M.T.B.; Writing—review and editing, all authors. All authors have approved the submitted version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** This work was supported by the Slovenian Research Agency (Young researcher number 53536 and the research program P1-0195: "Geoenvironment and Geomaterials"). The authors would like to thank the Slovenian Administration for Civil Protection and Disaster Relief and the Ministry for Defense for financing the project Masprem, and the Slovenian Environment Agency (ARSO) for providing rainfall and rain gauge data. The authors would also like to thank the two anonymous reviewers and the editor for their constructive comments that helped to improve the manuscript. The code of CTRL-T was written using the R open-source software and can be freely downloaded at: http://geomorphology.irpi.cnr.it/tools/rainfall-events-and-landslides-thresholds/ctrlt-algorithm/ctrl-code/ctrl\_t\_code.r/view. An example of the input files required by the algorithm can be freely downloaded at: http://geomorphology.irpi.cnr.it/tools/rainfall-events-and-landslides-thresholds/ctrl-t-algorithm/ input-demo/INPUT.zip/view.

**Conflicts of Interest:** The authors declare no conflict of interest.
