Okihiro Osaka, Fumitoshi Imaizumi
Our laboratory studies sediment disasters, forest hydrology, and revegetation technology. We are trying to clarify interactions among water, soil, and vegetation in mountain areas (e.g., Southern Japanese Alps, Mt. Fuji, experimental forests in our university) using various methods including field surveys, field monitoring, remote sensing, and GIS analyses.
Occurrence of landslides and debris flows causes severe sediment disasters every year in Japan and other countries in the world. In order to prevent sediment disasters, we are trying to clarify initiation mechanisms of landslide and debris flow based on field monitoring and analyses of topographic data obtained by airborne laser scanning and SfM (structure from motion) using UAV (unmanned aerial vehicle). Analysis of satellite images is also an effective method to evaluate risk of sediment.
Forests prevent abrupt water supply from hillslopes into rivers networks during heavy rainfall events, resulting in reduction of floods in downstream areas. Forests also moderate changes in the discharge in rivers by keeping water in the soil. For the better understanding of such effects, we investigate hydrological processes in forested mountain catchments.
Revegetation technology on the bare areas is also one of the main study topics in our laboratory. It is important to understand effects and limitations of vegetation on prevention of surface erosion and landslides. We are conducting field surveys on spatial distribution of root network to evaluate reinforcement of soil strength by the root networks.
A full view of the Ohya landslide, one of the largest landslide in Japan. We are conducting field observations in this landslide to clarify initiation mechanism of the debris flow.
View in initiation zone of the debris flow in the Ohya landslide
Survey of root network of Japanese cypress
Measurements of tree heights on the slopes with recent forest recovery.
Observation of stream discharge in a mountainous torrent.