Do standing trees affect landslide mobility on forested hillslopes in Japan?

Abstract

Landslide mobility likely changes in response to the effects of standing trees on the landslide runout. However, the properties of standing trees that influence landslide runout are not well understood. In this study, the relationships between the properties of landslides and the heights of standing trees and the runout distances of rainfall‐induced landslides (primarily 101–103 m3 in volume) in the Hiroshima Prefecture, Japan, were examined to investigate whether the heights of the trees around the runout area change the landslide mobility. The results indicate that the landslide runout was constrained not only by the landslide area and volume but also by the tree height around the runout area. Tall but sparse standing trees did not prevent landslide runout, whereas dense standing trees resulted in relatively low landslide mobility, irrespective of whether the trees were broadleaf or coniferous. A comparison between our landslide inventory and previously reported landslides showed that the landslide mobility was lower in areas with standing trees than in areas without standing trees, such as under experimental conditions and for landslides in Martian and submarine environments. Therefore, differences in the heights of the trees around the runout area can result in variations in the extent of landslide‐related hazards and disturbances.