## 5 Discussion
Moreover, vegetation canopies can be an obstacle in this application, as they can appear as a false terrain surface in photogrammetric analysis. In particular, the issue can manifest if dense and tall vegetation that is present before the event has been affected by the mass movement phenomena during the event. In this case, it can lead to an overestimation of changes in the DoD; therefore, attention should be paid to the results in such locations by using vegetation removal or filtering [40; 41]. In the present application, there was no such problem since the vegetation was sparse and low. Finally, it has to be noted that additional difficulty comes from the handling of large datasets and the requirements in terms of computational resources to reduce processing time. Overall, the findings indicate that a sequence of a UAS-derived imagery series in the form of continuous or regular monitoring can be particularly useful to monitor the earth's surface gravitational processes and their evolution [94; 95]. Particularly in the case of highly visited coastal areas, it can also delineate high-risk areas providing a better understanding of where safety is compromised. In this sense, an important practical implication of using UAS-derived monitoring of slopes is that it can be useful in microzonation of areas of interest, to offer a better balance between retaining safety of users/visitors but at the same time allowing the use of the site so that it will continue to support the development of a region in a more sustainable framework. Taking into account the previous discussion, during the design and selection of slope failure protection works, it is imperative to take into account the type and properties of failures that may be caused by the occurrence of not only geophysical (earthquakes) but also hydro-meteorological hazards (rainfall), in order to increase the safety factor of the slope and to achieve a safe stay of visitors in the area. It is important to note that both the seismic sequence in early 2014 and Medicare Iancos occurred during the winter and autumn seasons, respectively, i.e., during periods when traffic in the coastal area of Myrtos and particularly on its beach was limited. Furthermore, another useful point emerges from this application. In an area that is already known for its susceptibility to landslides (Myrtos has been characterized as an area of critically high susceptibility to landslides [50]), individual susceptible segments can be defined with greater precision and mapped with higher resolution using the proposed approach. By highlighting these areas (Figure 12), the authorities involved in the prevention and management of disasters induced by natural hazards have at their disposal a valuable tool for taking effective measures to limit the adverse conditions and the unpleasant impact on the local population and visitors, as well as on the existing adjacent buildings, networks, and infrastructure. Furthermore, they can select segments of low susceptibility to slope failure and use them for safe accommodation, for expanding related facilities and infrastructure, or any other use appropriate for such a valuable highly visited site. The highly detailed observations allowed by the proposed approach were a unique opportunity to shed light on the synergy between hydro-geomorphic processes and the active tectonic deformation of rock formations, showing the strong relationship between geological and tectonic characteristics and erosion/sedimentation processes which continuously shape the landscape.