**5. Discussion**

Using RES and GIS techniques, the landslide susceptibility of the Attica Region was assessed by correlating ten parameters and producing the final susceptibility map for the whole Attica peninsula (with its islands included) in Greece. The validity of this approach was tested using the slope failures that were recorded during the last sixty years in this region. In particular, 68% of the recorded 220 slope failures were found to be in the "Extremely high susceptibility" and 21% in the "Landslide" zone respectively of the developed map. Studying more carefully this map, some more remarks can be extracted.

Initially, it is shown in the susceptibility map that slope failure incidents are located mostly in areas where Neogene and Quaternary sediments outcrop. Secondarily, slope failures are associated with carbonate rocks basically due to rockfalls. In order to preliminary assess the potential landslide risk in respect to settlements, the villages and cities at the study area were plotted on the susceptibility map (Figure 11).

This correlation suggests that 16 settlements are entirely located within "Landslide" and 201 urban areas are in the "Extremely high landslide susceptibility" zone. To be more specific, in the "Landslide" zone, places such as Chalkoutsi, Grammatiko, Kato Alepochori, Schinos can be found. In the "Extremely high landslide susceptibility" zone, characteristic sites are Mesagros (Aegina Island), Varnavas, Galaniana (Antikithira island).

In addition, many defined slope failure areas are associated with the existence of faults. This result should be taken into consideration by public authorities responsible for the construction of public technical works, regarding urban planning and design of new infrastructure projects (e.g., highways, tunnels, major buildings).

According to the generated susceptibility map, areas associated with an instability index greater than 70% are located in many sites around the Attica region (islands included). For that reason, public authorities responsible for civil protection need to ge<sup>t</sup> advice from

such maps to make emergency plans at different administrative levels, useful for the pre-event of the landslide risk managemen<sup>t</sup> cycle.

Moreover, the landslide susceptibility map can be used with the already produced potential highly flood hazard zoning maps of Attica Region authorized by the Greek Ministry of Environment and Energy, and with the produced flooded area maps, delivered by the Copernicus Emergency Management Service-Mapping.

Concerning localities that were affected by catastrophic forest fires in previous years such as those of Kineta (2018) and Mati (2018) (Figure 11) [38], and studying the generated susceptibility map, it is realized that such fires can cause in the immediate future "secondary" hazards like earth slides, debris flows and flash floods. Those two areas are associated with an instability index greater than 53% and this means that the drastically changed environmental conditions due to the fires may increase the landslide activity in the area in the near future.

Finally, it should be pointed out that the developed susceptibility map is at a regional scale (1:100,000) and its practical use is to be applied in conjunction with site-specific work, from experts such as experienced geologists, geotechnical engineers before development takes place. Additionally, it should be mentioned that even though susceptibility analysis does not define either the time and the type of the failure, or the volume of the mass involved, it is necessary for the estimation of hazard and risk index and zoning, respectively.

For all these reasons, the applied methodology (RES and Oregon Protocol methodology) should be accompanied each time by the appropriate fieldwork as well as the necessary geotechnical desk study, so as to acquire the most accurate geological model of the ad hoc examined area susceptible to slope failure [55].
