**4. Conclusions**

A nation-wide quantitative landslide risk assessment is not ye<sup>t</sup> feasible in Italy (301,304 km2) because of the lack of homogeneous, complete and detailed data. In this work we partially fill this gap by proposing a set of indicators to characterize landslide risk. Indicators are simple numerical indexes widely used in environmental studies by scientists and governmental agencies to simplify and describe complex phenomena. By definition, indicators should be simple and easy to measure, update and understand.

Firstly, a spatially distributed landslide risk index (LRI) was obtained combining state-of-the-art nation-wide susceptibility maps and a soil sealing map released in the framework of a governmental monitoring program of the urban expansion. While the former account for hazardous areas, the latter indicates if anthropic elements could be exposed; their spatial overlapping defines the relevance of the degree of risk.

LRI was then aggregated at the municipal scale to define the average landslide risk index (ALR) and the total landslide risk index (TLR), expressing respectively how hazardous the areas occupied by settlements or infrastructure are, and how serious the overall risk level in each municipality is. ALR and TLR proposed in this work are simple to update and can be adapted to various contexts and scales; in this test they were applied at the municipal level because municipalities are the key administrative subdivisions involved in urban development, land planning and risk mitigation strategies. The proposed indexes cannot substitute a detailed quantitative risk assessment, nevertheless they can provide a preliminary outlook on the spatial distribution of landslide risk at a national scale, and they can be used to evaluate how cautionary each municipality has been in planning its development to deal with the geomorphological hazards threatening its territory.

**Author Contributions:** Conceptualization, S.S.; methodology, S.S.; investigation, F.C., S.S.; data curation, S.S.; writing—original draft preparation, S.S., F.C.; writing—review and editing, S.S.; visualization, F.C.; supervision, S.S. Both authors have read and agreed to the published version of the manuscript.

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

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Part of the input data used for this study are accessible online at https: //www.istat.it/it/archivio/222527 and http://groupware.sinanet.isprambiente.it/uso-coperturae-consumo-di-suolo/library/consumo-di-suolo (last accessed on 31 May 2021). The new data presented in this study are available on request from the corresponding author.

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