**6. Conclusions**

This study presents the landslide susceptibility analysis for Attica Region, which is the most densely populated area in Greece. The produced susceptibility map is a cartographic product in a regional scale (1:100,000) generated for the Attica county via a semi-quantitative heuristic methodology named Rock Engineering System and a prototype technique originally developed by the Oregon Department of Geology (USA). To the author's knowledge, this is the first time that such an in-depth analysis has been conducted for the whole of Attica county. Furthermore, for the compilation of this map, RES methodology was applied as a simple and fast tool for the calculation of the instability index of each examined slope failure recorded in a well-organized geodatabase according to the EU Inspire Directive.

Considering the mentioned previously, it should be noted that 68% of the locations of actual and potential landslides correspond to the "Extremely high" and 21% are associated with a landslide. Responding to the previous remark, particular sites in Northeastern Attica (e.g., Kapandriti, Varnavas, Oropos, Kalamos), historical slopes in Western Attica (such as those of Alepochori-Psatha, Alepochori-Schinos, Kakia Skala), the most well-known historical landslide of Malakasa, characteristic places in Attica islands (e.g., Kithira-Kapsali, Aegina-Kakoperato, Salamina-Porto Fino) were validated through the above–mentioned methodology and it was found that all of them were confirmed as landslides (Figure 11). Furthermore, this correlation suggests that 16 settlements are entirely located within "Landslide" and 201 urban areas are in the "Extremely high landslide susceptibility" zone.

As in Section 3.2 is mentioned, RES methodology was applied in different physiographic environments with a variety of geological and tectonic settings and scales. In the present study, the previous statement was confirmed by implementing RES in an area with complex geological settings (e.g., active faults, many different streams based on Strahler classification as well as a variation of geological formations). Thus, it is suggested that this procedure (i.e., RES, GIS techniques, Oregon protocol-Special Paper 42) could be used in other regions with different geological environments and tectonic characteristics.

Summarizing, the DIAS geodatabase represents the spatial distribution of over 300 landslides (rockfalls, falls, erosion lines included) based on published and unpublished information, field observations and remote sensing techniques. The intention is that the database should be updated constantly. The outcome of the DIAS project will be accessible to the public, through a web-based platform using an open-source G.I.S. software so as to aid awareness of landslides among different stakeholders (e.g., landslide experts, governmen<sup>t</sup> agencies, planners, citizens). Moreover, the DIAS project can facilitate the role of Civil Protection Authorities, by providing inputs for prevention and preparedness.

Taking into consideration the previous outcomes, the upcoming steps of this research (DIAS project) will be the generation of hazard and risk maps using triggering dynamic factors like earthquake and rainfall data, as well as different elements of risk, respectively, in specific areas.

**Author Contributions:** Conceptualization, N.T. and G.P.; methodology, N.T. and G.P.; software, N.T. and P.A.; validation, N.T., G.P. and A.G.; formal analysis, N.T., G.P. and A.G.; investigation, N.T.; resources, N.T., G.P. and A.G.; data curation, N.T., G.P., A.G. and P.A.; writing—original draft preparation, N.T.; writing—review and editing, N.T., G.P., A.G. and P.A.; visualization, N.T.; supervision, G.P., A.G.; project administration, N.T., G.P.; funding acquisition, N.T., G.P., A.G. and P.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was co-funded by Greece and the European Union (European Social Fund-ESF) through the Operational Program "Human Resources Development, Education and Lifelong Learning 2014–2020" in the context of the project "Landslide Risk Assessment of Attica Region" MIS (5050327).

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

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** The authors are grateful to the Greek Ministry of Environment, Region of Attica, Hellenic Survey for Geology and Mineral Exploration (H.S.G.M.E.), General Secretary of Civil Protection of Greece and Greek Cadastre S.A. for providing valuable technical landslide reports as well as crucial digital geodata records. Furthermore, rainfall data were provided by the Institute for Environmental and Sustainable Development Research (IEPBA) of the National Observatory of Athens.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
