# UAV-Based Evaluation of Rockfall Hazard in the Cultural Heritage Area of Kipinas Monastery, Greece
## 4 Rockfall Hazard and Risk Assessment
### Results  
The proposed Rockfall Hazard and Risk Rating System was applied at the four (4) predetermined sub-regions (U1 to U4, Figure 3) along the rock cliff of Kipinas Monastery. Since these locations are in the same area, some of the factors (mostly spatial related) have the same rating for all four, whereas some differ for each slope section. In particular, 12 out  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Category** & **Factor** & **Weight** & & **Rating** & \\ \hline \multirow{6}{*}{D.} & **20.** Rock mass permeability & \multirow{2}{*}{3\%} & Very high & High & Moderate & Low \\  & **Rating** & **10** & **30** & **60** & **100** \\  & **21.** Seismic acceleration & \multirow{2}{*}{4\%} & \textless{}0.16 & 0.16–0.24 & 0.24–0.36 & \textgreater{}0.36 \\  & coefficient (m/s\({}^{2}\)) & & **10** & **30** & **60** & **100** \\  & **Rating** & \multirow{2}{*}{15\%} & Negligible & Low & Moderate & High \\  & **Rating** & & **10** & **30** & **60** & **100** \\  & **23.** Value of structures & \multirow{2}{*}{15\%} & Negligible (i.e., & Low (i.e., & \textless{}0.0  
of 23 factors have the same rating. After extensive application of this rating system to the investigated site, the total scores were categorized, according to Table 8 for hazard and Table 9 for risk estimation. The final result of the application is a hazard and risk zonation of the cliff against rockfall occurrence, presented in Table 10 and in Figure 21.  
Sub-region U1 is categorized in the moderate hazard zone, mainly due to the low height of the potential rockfall release zone and also due to the small sizes of the prone blocks. However, due to the high human presence and the high structure of the involved structure (in this sub-region is located the monastery), the total risk is high. The hazard levels in the area U2 are high, mainly as a result of the moderate-to-large volume of the prone blocks and their notable total kinetic energy at the location of impact with the road. However, the lack of significant structures in this location (only a road is located in U2) and the medium human presence (location of a resting area along the main road) result in a moderate total risk level. Sub-region U3 is the only one with both a high hazard level and high risk level. This occurs primarily from the notable large volume of the prone rock blocks which could be released from a significant height (47 m) which is greater than 2/3 of the total slope height. Additionally, the residencies of the monks are located in U3; the impacts of a potential rockfall event in this area would be very important. In the last investigated location (U4), both the hazard level and the risk level are moderate. The size of the prone unstable blocks is not large, in contrast with the dense spatial distribution shown, which occurs from the small dimensions of the area. Additionally, in this area there is a catchment zone, even if it is very restricted. The value of the structures is low, because only the road is located there, and the human presence is below moderate levels.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sub-Region** & **Hazard Score** & **Hazard Level** & **Risk Score** & **Risk Level** \\ \hline U1 & 40 & III (Moderate) & 70 & IV (High) \\ \hline U2 & 46 & IV (High) & 59.5 & III (Moderate) \\ \hline U3 & 53.54 & IV (High) & 77.45 & IV (High) \\ \hline U4 & 41 & III (Moderate) & 50 & III (Moderate) \\ \hline \hline \end{tabular}
\end{table}
Table 10: The hazard and risk assessment results for each sub-region in Kipinas Monastery.  
Figure 21: The visual interpretation of the results of the rockfall hazard and risk assessment with: (**a**) the hazard map and (**b**) the risk map along the cliff of Kipinas monastery.