in the area of Aso Mountain and the central part of Kyushu Island. Aso Mountain is
an active volcano with steep slopes. Volcano activity may be considered one of the
major reasons for frequent shallow landslides in this area. The high potential risk in
central Kyushu Island may be related to the steep slope of the mountain area and the
extreme rainfall events such as typhoons which often pass through central Kyushu
Island.
11.5 Discussion
The mean monthly shallow landslide risk map can be used to identify where the
most dangerous area of shallow landslides is and inform local residents of areas to
avoid during the extreme rainfall events. The hydrogeotechnical model is a gridcell distributed model which has two main sub models; namely hydrological sub
model and infinite slope instability model. The hydrological sub model considers
Table 11.2 Shallow
landslide potential risk levels
Percentage (%)
Risk levels
0–10
Stable
10–30
Low potential risk
30–85
Middle potential risk
85–98
High potential risk
98–100
Highest potential risk
Fig. 11.10 Mean risk of the shallow landslides (2000–2008): (a) Mean risk of whole Kyushu
Island, (b) Mean risk of the center part in Kyushu Island
11 Modelling Shallow Landslide Risk Using GIS and a Distributed. . .
237