## 4 Case Study  
The preliminary findings of this study strongly recommend a comprehensive project including pilot site investigations, and laboratory and in situ measurements as a future study. Yet, a representative case study of a slope failure triggered by rainfall is modelled  
Figure 9: The schematic form representing the flow of the study. based on independent and unbiased data and laboratory findings. A slope failure was announced on 11 September 1999 in Hwangyeong Mountain, Busan, South Korea which caused the loss of one life, three injuries, and approximately 9.9 million US dollars of restoration expenditure [10]. Following the devastation caused by the landslide, a project was carried out including the in situ measurements of rainfall and pore pressures, and [PERSON] et al. [10] published a modeling study investigating the slope failure in Hwangyeong Mountain with site-specific characteristics. Their study included soil properties such as the as average values of Hwangyeong Mountain soils, given in Table 3, and used a simplified soil profile (Figure 10) to represent the geometry of the failed slope [10]. The soil characteristics and the soil profile were adopted and the proposed procedure in this study was conducted to be presented as a case study. The rainfall conditions were obtained by researching both the related study and recorded historical data as well. [PERSON] et al. [10] reported a total rainfall of 200 mm for 3 days (9-11 September 1999) and the highest hourly rainfall during this period as 39 mm/h. For any specific date, it is possible to access the records of an airport located close to Hwangyeong Mountain where the slope failure was found via an Internet web page, namely, Weatherspark. The Weatherspark web page uses METAR and Integrated Surface Database (ISD) reports. The METAR code is regulated by the World Meteorological Organization in consort with International Civil Aviation. ISD reports are maintained and published by the National Oceanic and Atmospheric Administration's (NOAA) National Center for Environmental Information. The web site uses ISD data to complement and backfill for their METAR archive. The Weatherspark web page allows users to access a multitude of station records, predominantly airport records, for a specified date and location. Taken from Weatherspark, the rainfall records from Gimhae International Airport for September 1999 are presented in  
Figure 10: The slope model used in [PERSON] et al. [10]. Directly taken from [10]. \begin{table}
\begin{tabular}{l c} \hline
**Property** & **Case Study** \\ \hline Dry density (kg/m\({}^{3}\)) & 1250 \\ Drained cohesion (Pa) & 100 \\ Drained friction angle (degrees) & 33 \\ Saturated hydraulic conductivity (m/s) & 1.97 \(\times\) 10\({}^{-6}\) \\ Porosity & 0.46 \\ van Genuchten parameter, a & 0.520 \\ van Genuchten parameter, \(P_{0}\) (MPa) & 0.003 \\ \hline \end{tabular}
\end{table} 
Table 3: Some geotechnical and hydromechanical properties of the soil subjected to rainfall in the study of [PERSON] et al. [10]. Figure 11[39]. The precipitation that caused the collapse is marked with a dashed line on the figure. Precipitation characteristics may vary with distance or altitude. In this instance, the rainfall record was on September 10 and no other rainfall was recorded a day before and after (9 and 11 September) in Figure 11; however, [PERSON] reported a total of 200 mm of rainfall in 3 days. Thus, for a robust precipitation process, a comparative analysis of [PERSON] et al. [10]'s and the station data [39] has been established. The station data in Figure 11 indicates that a thunderstorm with rain lasted a minimum of 2.5 h with an antecedent heavy rainfall which also had an antecedent light rainfall.