2011 Volume 64 Issue 3 Pages 46-56
Shinmoedake in Kirishima volcano erupted violently on January 26, 2011 and spewed a large amount of ash over the surrounding area, especially eastward and southeastward, in the following several days. From the viewpoint of a debrisflow hazard we examined thickness and grain size of ash deposits, infiltration properties of tephra-covered slopes, and sediment movement in the upper Takasaki River basin and the southern area of Takachihonomine after the eruption. Onsite tests for infiltration capacity of the slopes revealed a lower rate in the upper Takasaki River basin than that of the southern area of Takachihonomine, reflecting thicker deposits of fine-grained ash in the former basin than that of the latter area. This is probably the reason why sediment movement in the upper Takasaki River basin is more active than that of the southern area of Takachihonomine.