Abstract
The bedrock of Kitamata Vally in the Name River is formed by granite, which is easily weathered for its soil condition. Therefore, many typical stony debris flows has been generated especially in Kitamata Valley. Since the debris flow observation has been started in 1982, seven debris flows has confirmed, and four debris flows was filmed in the VTR.
This paper presents the condition of generation and the discharge of debris flow, using analyzing VTR, aerial photo interpretation, also fields surveying. As a result, we recognized two-generation case of debris flows. The first type was that the debris flows generated by the slope collapses and the second was the riverbed deposits were turned to debris flow. These debris flows were divided into the three phases of the primary flow, the flow of large stone concentrated and the following flow consisted of water and fine materials, from the VTR observation. And also, there were many variations as the remarkable peak runoff, few times peak runoff, and many abrupt waves, in these flow shapes. Further, the maximum each value of the debris flows velocity, discharge and wave height generally appeared at the coming down of the debris flow peak with concentrating large stone, but these values partially appeared at the primary flow and the following flow. The behavior of the large stones of which the diameter of 1.0-1.5m or less flew down with revolving movement and the diameter more than 1.5 m flew down as if they were floating on the water.
