# UAV-Based Evaluation of Rockfall Hazard in the Cultural Heritage Area of Kipinas Monastery, Greece
## 4 Rockfall Hazard and Risk Assessment
### Rockfall Hazard and Risk Rating System  
In the present study, a qualitative rockfall hazard and risk rating system is proposed. This rating system was designed with an emphasis on the rating of natural rock slopes, which indicate a susceptibility to rockfall events with a significant impact on human structures and activities. The above criteria in this particular case were fulfilled by the investigated site, the cultural heritage area of Kipinas Monastery in Epirus, Greece. In general, four (4) major parameter categories are defined, which consist of a variety of different ranking values, in order for the total risk level for each sub-region to be estimated. Three (3) of these categories are related to the hazard level and one (1) to the impact of a potential rockfall event. In this assessment, every rating parameter has a different weight, which is based on the significance of each individual contribution to either the hazard and/or the risk level for every sub-region. The four main categories are presented in Table 6.  
In particular, the first category (A) of the rating system is related to the geometry and the morphology of the slope in general. It involves parameters such as the height, \begin{table}
\begin{tabular}{c c} \hline \hline
**Major Category** & **Weight in Risk Level (\%)** \\ \hline A. Geometry Factors & 30 \\ \hline B. Geoengineering Factors & 30 \\ \hline C. Triggering Factors & 10 \\ \hline D. Impact Factors & 30 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The main categories of rating factors and their weight for the proposed rating system. the angle, the roughness and the vegetation of the slope, the main height of the rockfall source area and the availability of obstacles and vegetation in the catchment zone at the footway of the slope. Category B involves the engineering geological factors of each slope. These factors describe the condition of the rock discontinuities, the intact rock strength, the rock mass structure, the weathering level of the rock mass, the spatial distribution of the predetermined rock blocks (already fallen and prone) per slope, the volume of the dominant rock blocks (already fallen and prone) and the potential kinetic energy of a rockfall at the location of impact with the ground. The parameters in the third major category (C) are related to the potential triggering factors, and feature the rainfall conditions and their severity, the drainage conditions of the rock mass and the seismicity of the area. The last category (D) refers to the impacts of a potential rockfall event and contains factors related to the human presence and the value of the pre-existing structures. As mentioned before, the weight for each category varies, depending on the importance of the parameters involved. Specifically, in this assessment, category A, B and D are given a weight of 30% each and category C 10% to the total risk score for every investigated sub-region. The factors of each category and their individual weights are presented in Table 7.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt}} \hline \hline
**Category** & **Factor** & **Weight** & & **Rating** & & \\ \hline \multirow{8}{*}{A.} & **1. ** Slope height (m) & 5\% & \textless{}10 & 10–30 & 30–60 & \textgreater{}60 \\  & **Rating** & & **10** & **30** & **60** & **100** \\  & **2. ** Slope angle (\({}^{\circ}\)) & 7\% & 20–45 & 45–55 & 55–70 & \textgreater{}70 \\  & **Rating** & & **10** & **30** & **60** & **100** \\  & **3. ** Slope roughness & 2\% & Planar rough & Planar smooth & Inclined smooth & Inclined rough \\  & **Rating** & & **10** & **30** & **60** & **100** \\  & **4. ** Main seeder height (m) & 8\% & \textless{}H/4 & \textless{}H/4–H/2 & \textless{}H/2–2H/3 & \textless{}H/3–H \\  & **Rating** & & **10** & **30** & **60** & **100** \\  & **5. ** Slope vegetation & 3\% & Dense (high trees) & Dense (low bushes) & Sparse & None \\  & **Rating** & & **10** & **30** & **60** & **100** \\  & **6.