Abstract
Condition of vegetation is important factor for considering possibility of slope failure, as well as condition of topological structure such as slope degree and convexity. Previous studies have revealed that roots of trees might prevent erosion of surface soil which leads to slope failures.
There are three factors that might be related to slope failure prevention, thought to be able to be acquired from LIDAR (Laser Imaging Detection and Ranging) data. That is height of trees, number of trees and breast high diameter. These factors were previously very hard to acquire widely as field survey was the only way to get accurate data, and data collecting area was limited. However, accumulation of LIDAR data has made it possible for wider area simultaneously.
This study showed that height of trees can be obtained more correctly from LIDAR data in a state of relatively harmonized with possibility of slope failure occurrence. Also assuming number of trees is possible when considering the number might be estimated smaller in steep slopes compared to gentle slope. In contrast with those, possibility of acquiring information relating breast high diameter might be different among type of trees. Thus, while assuming accumulation of cross-sectional area at breast height were seemed to be acquirable at evergreen needle leaf forests such as plantation of cedars, those assumption were almost impossible at deciduous broad leaf forests such as secondary forests of Quercus serrata in the case of Izumozaki district where many slope failures brought by heavy rainfall in 2004.
