## 5 Discussion  
This work used UAS-aided photogrammetry and TLS in tectonically active segments of the coastal zone as a tool to improve our understanding of the mass-movement processes and the spatial dimension of landslide risk through a highly localized lens, as an approach that improves our capabilities in coastal management in slope-failure-prone areas. The outcome of the two applications at Egremnoi and Porto Katsiki beaches is a strong indication these cutting-edge technologies have the capabilities to produce valuable results in the field of slope failures, allowing the identification of higher-risk zones and relative prioritization of any interventions. Given the significance of slope failures as a hazard in coastal cliffs and the extent of its impact acknowledged in the introduction of the present study, rock slope stability analysis is considered very important for reducing the effects of instabilities and increasing the safety of adjacent or neighboring areas, while preserving the value of the sites in question. However, the classical survey methods comprising conventional data collection, which have been proposed and applied in various environments and settings (e.g., [104; 105], present significant problems. These problems have to do with the time and cost needed for implementing fieldwork, the safety of researchers during data acquisition and the coverage of the data collection [106; 107; 43; 108]. The visual inspections close to steep slopes, scarps and cliffs and direct measurement conducted by the researchers, who act as rock climbers, affect their safety during the field survey by exposing them to potential failure impacts. Furthermore, some discontinuities cannot be directly observed during visual inspections and are partially recorded and mapped, unless suitable aerial or satellite imagery is used. Consequently, a limited number of manual compass data measurements of dip and dip direction can be collected during the implementation of the classical survey methods in steep slopes, affecting the results as discontinuities measured in small areas are not representative of the whole rock masses. If an effort is made to fully cover the slopes, then field data acquisition may be a time-consuming and expensive procedure. In the case of rock slope stability analysis on the coastal slopes of Egremnoi and Porto Katsiki, the classical methods, which include surveys with a geological compass measuring dip and dip direction directly on the discontinuity, face many problems, which are strongly related and attributed to the geological and geomorphological structure. These issues are strongly related to the current geological and geomorphological setting of western Lefkada. Its tectonic structure is characterized by active and seismic faults, which, in combination with other morphological discontinuities, form a geotechnically unstable area with high and steep slopes composed of highly fractured, brecciated, unsupported and almost powdered geological formations, mainly limestones of the Paxoi geotectonic unit with secondary welding and extensive semi-cohesive scree with limestone breccia and red-clay-filled fractures as well as similar geometries of beds and discontinuities. These intense tectonic processes have a great impact on the geomorphology of the study area. They have increased the height and inclination of slopes resulting in almost vertical slopes with maximum elevation larger than 100m in several sites. In addition, the combined action of (i) endogenous processes, including deformation, which has caused lithological heterogeneity and mechanical anisotropy of the alpine formations and post-alpine deposits, and (ii) surficial processes including repeated cycles of mechanical, chemical and organic weathering and marine and aeolian erosion, have contributed to decreased cohesion and formation loosening along the steep coastal slopes.