When a large scale sediment-related disaster occurs, it is imperative to take quick action to prevent the disaster from expanding, such as the evacuation of residents in the area and emergency restoration of the desaster site. In order to examine concrete measures, it is necessary to have a detailed grasp of conditions at the disaster site. Up until now information has been collected through field investigation and observation from the ground. However, when a large-scale disaster occurs, since it is difficult to carry out an investigation over an extended area in a short period, and the approach to the disaster site is often limited immediately after a sisaster, there are limitations on information gathered from the ground soon after a disaster. Investigation from a helicopter has advantages such that it is possible to observe an extended disaster site in a short period and that it is also possible to collect information at the site where no surface access is available. On the other hand, because of the limitations in data accuracy due to types and functions of sensors, a helicopter investigation seems to present difficulties in grasping any portentous symptoms which could indicate a secondary disaster. Therefore, in order to make it possible to collect information quickly and efficiently using a helicopter at the time of a sediment-related disaster, helicopter sensors and the contents for the investigation from the air were examined. Measures to get information on sediment-related disaster using a helicopter were reviewed also by interpreting past video films and conducting mock investigations on a disaster site using a helicopter.
As comfortable lives are demanded nowadays, we begin to take an interest in near mountain torrents. It seems that constructing sabo facilities in such a mountain torrent affect migratory fishes. So we investigated fish ladders on sabo facilities in the whole country by questionnaire. As a result of the investigation, some questions and consideration of fish ladders become clear. We consider the rate of satisfaction for fish ladders, but it is difficult to propose the best structure of fish ladders on account of a lack of examples. We intend to examine fish ladders where fishes can go upstream easily in consideration of the sediment runoff and hydraulic condition of mountain torrents where sabo facilities are built. And we make another attempt to investigate not only fish ladders but also means of environmental preparation which is comfortable for fishes in whole watershed.
This paper discussed the experimental results on physical and mechanical properties of the Sanbagawa crystalline schist and the Mikabu green rocks which form Yoshino river basin in the outer zone of southwest Japan. It was clarified that the physical and mechanical properties of rocks (black schist, green schist, diabase green rocks, taff green rocks etc. ) were different. The landslide occurred at the area of weathered black schist and taff green rokcks. As to the physical properties of these rocks, the porosity was large and the elasticity and rigidity moduluses and the compression strength were very small, moreover the failure pattern was ductile failure.