# Assessment of Internal and External Factors Causing Slow-Moving Landslides
## 3 Results and Discussion  
### Overlap Analysis  
The slow-moving landslide area was overlapped on the landslide hazard map to analyze the difference in the risk of occurrence of slow-moving landslides and general landslides. The percentage area occupied by slow-moving landslide regions on the landslide hazard map was highest in the excluded non-hazard area at 28.8%, followed by Grade 3 at 25.8% and Grade 4 at 17.5%. Regarding the characteristics of each slow-moving landslide area, Sites No. 2, 10, and 13 had area ratios of 92.4, 79.5, and 68.3% of the excluded area, respectively, which were significantly different from the data on the hazards of the occurrences of slow-moving landslides and general landslides. In addition, Site No. 8 had an area ratio of 66.1% for Grade 5, and Site No. 15 had an area ratio of 53.5% for Grade 3. Thus, 83.3% of the area (including excluded areas) was in Grade 3 or lower, which is a moderate hazard (Table 1). Landslides in South Korea and slow-moving landslides are different forest soil sediment disasters with geology, soil, topography, cause, and slope differences [11]. Because the landslide hazard map was created using landslide triggering factors, the slow-moving landslide areas in the landslide hazard map were judged to include low hazard grades and especially grade-excluded areas. We analyzed the statistical significance of the results of the overlap analysis, i.e., the difference in area by grade. Specifically, we conducted normality testing of the area data \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Site No.**} & \multicolumn{6}{c}{**Grade of Slow-Moving Landslide on the Landslide Hazard Map (m\({}^{2}\))**} & \multicolumn{1}{c}{**Total**} \\ \cline{2-9}  & **Grade 1** & **Grade 2** & **Grade 3** & **Grade 4** & **Grade 5** & **Excluded Area** & **(m\({}^{2}\))** \\ \hline \multirow{3}{*}{1} & 1900 & 13,500 & 10,400 & 3700 & 100 & - & 29,600 \\  & (6.4) & (45.6) & (35.1) & (12.5) & (0.3) & (-) & (100.0) \\  & 500 & 1700 & 1200 & 1300 & 200 & 59,900 & 64,800 \\  & (0.8) & (2.6) & (1.9) & (2.0) & (0.3) & (92.4) & (100.0) \\  & - & 14,300 & 20,700 & 12,900 & 800 & 35,200 & 83,900 \\  & (-) & (17.0) & (24.7) & (15.4) & (1.0) & (42.0) & (100.0) \\  & 310 & 20,100 & 25,500 & 19,700 & 6100 & 200 & 74,700 \\  & (4.1) & (26.9) & (34.1) & (26.4) & (8.2) & (0.3) & (100.0) \\  & - & 1400 & 12,200 & 4100 & - & 6200 & 23,900 \\  & (-) & (5.9) & (51.0) & (17.2) & (-) & (25.9) & (100.0) \\  & 100 & 2600 & 8600 & 6300 & - & 10,800 & 28,400 \\  & (0.4) & (9.2) & (30.3) & (22.2) & (-) & (38.0) & (100.0) \\  & - & 3800 & 22,900 & 5800 & - & 20,000 & 52,500 \\  & (-) & (7.2) & (43.6) & (11.0) & (-) & (38.1) & (100.0) \\  & 200 & 2900 & 3700 & 23,600 & 59,400 & - & 89,800 \\  & (0.2) & (3.2) & (4.1) & (26.3) & (66.1) & (-) & (100.0) \\  & 3200 & 3800 & 2400 & - & - & 3300 & 12,700 \\  & (25.2) & (29.9) & (18.9) & (-) & (-) & (26.0) & (100.0) \\  & 500 & 600 & 400 & - & - & 5800 & 7300 \\  & (6.8) & (8.2) & (5.5) & (-) & (-) & (79.5) & (100.0) \\  & 4800 & 14,800 & 26,300 & 2700 & 300 & 2800 & 51,700 \\  & (9.3) & (28.6) & (5.9) & (5.2) & (0.6) & (5.4) & (100.0) \\  & 4200 & 10,200 & 9700 & 300 & - & 3000 & 27,400 \\  & (15.3) & (37.2) & (35.4) & (1.1) & (-) & (10.9) & (100.0) \\
13 & - & 100 & 4400 & 8000 & - & 26,900 & 39,400 \\  & (-) & (0.3) & (11.2) & (20.3) & (-) & (68.3) & (100.0) \\
14 & - & - & 2500 & 12,700 & 6300 & 15,800 & 37,300 \\  & (-) & (-) & (6.7) & (34.0) & (16.9) & (42.4) & (100.0) \\
15 & - & 1600 & 18,900 & 13,900 & 900 & - & 35,300 \\  & (-) & (4.5) & (53.5) & (39.4) & (2.5) & (-) & (100.0) \\ Total & 18,500 & 91,400 & 169,800 & 115,000 & 74,100 & 189,900 & 658,700 \\ (m\({}^{2}\)) & (2.8) & (13.9) & (25.8) & (17.5) & (11.2) & (28.8) & (100.0) \\ \hline \hline \end{tabular}  
* The values in parentheses represent the ratio of the area occupied by a slow-moving landslide site on the landslide hazard map.  
\end{table} 
Table 1: Results of overlap analysis of landslide hazard map and slow-moving landslide areas.