Study on the time variation of sediment discharge after gigantic landslide at volcanic area in south-east Asia

点击翻译按钮获取中文摘要

In order to examine the mechanism of gigantic landslide occurred at March 26, 2004 in the caldera of Mt Bawakaraeng, South Sulawesi, Indonesia and know the time variation of sediment discharge from deposition of the landslide mass, Field survey and the analysis of satellite images were carried out. The results are as follows.(1) Sediment discharge from deposition of Landslide mass was the largest at first year after landslide, then were greatly decreasing at second and third year. This tendency is quite same with the sediment discharge from the pyroclastic deposit just after the volcanic eruption. With the sediment discharge, gully erosion was going to developing at the landslide deposition. At first year, the width and depth of the gully became larger, while width of the gully was still became larger at second and third years. It means that gully side wall was greatly eroded at second and third years.(2) The analysis of the route of radioactive tracer was tried in order to know the runout distance of eroded sediment in the Jeneberang River which flows down from Mt Bawakaraeng. But because the amount of sampling of sediment discharge was too small for the radioactive tracer analysis, runout distance of the sediment could not be well made clear. More sampling of discharged sediment is necessary in order to attain the purpose.(3) The mechanism of occurrence of landslide was examined by geological and geotechnical methods. The weak laminar at the bottom of the collapsed slope was made clear to be the key of the landslide occurrence. It seemed that the laminar collapsed at first, and whole slope followed to move downward.