Relationship between Vegetation and Landslide Depth Using Statistical Methods: Aso Region, Kumamoto Prefecture, Japan

In recent years, climate change has led to an increased frequency and scale of heavy rainfall events, and subsequently, a rise in the occurrence of landslide induced by these rainfall events has been observed.Vegetation enhances slope stability by increasing soil strength through root systems.It is essential to quantitatively assess the influences that vegetation exerts on the occurrence of landslides and their depth to utilize vegetation to reduce disaster risk.Hence, in this study, we aimed to quantitatively evaluate the effects of vegetation diversity on the depth of landslides in the Aso region of Kumamoto Prefecture using statistical methods.We collected necessary data on topography, geology, vegetation, and rainfall and analysed them using a random forest.As a result of constructing the RF, the factors importance was the slope angle was the largest, followed by the landslide area, and the importance of vegetation was not large.As a result of creating partial dependence plots of the average landslide depth for each geology and vegetation type, the average landslide depth of secondary grasslands was approximately 20 cm smaller than that of broadleaf forests in all geological categories.This study could contribute substantially to future disaster mitigation efforts.