Probability model of landslide risk calculated with both triggering and resistance factors and comparison of landslide risk between in rainy region and in less rainy region

Abstract

A probability model of landslide risk evaluated with both triggering and resistance factors is proposed in order to compare spatiotemporally the tendency of landslide occurrence. Assuming a landslide tendency is the function of the intensity of triggering factors (such as rainfall or earthquake), we calculate a risk level as the summation of the product of the occurrence probability and the landslide tendency at an arbitrary intensity of triggering factors. This model enables us to discuss about the landslide risk together with the effects of immunity to rainfall triggering and increase in heavy rain due to climate change. In terms of immunity to rain fall, there are many arguments about relationships among the landslide tendency, critical rainfall to trigger landslides and regional rainfall characteristics. We applied this model to two cases of rainfall triggered landslides reported by previous articles, and compared the calculated risk levels in a rainy and a less-rainy region. The result in the first case shows that, the risk level in a rainy region is much higher than that in a less-rainy region. It is consistent with the landslide density map in Japan, On the contrary, the result in the second case demonstrates that neither the occurrence probability nor the landslide tendency are affected by the regional rainfall characteristics.