2018年7月広島県坂町総頭川で発生した流木を伴った土石流の特性

抄録

This paper describes the characteristics of the debris flow with drift wood which occurred in the Sozu River in Saka Town, Hiroshima Prefecture on July 6^th, 2018. Field survey and numerical simulation were made in this research. The field survey shows the amount of sediment and woody debris outflowing from the mountain area and the results are compared with the numerical simulation. One-dimensional simulation model is developed for the debris flow with drift wood. This model considers frontal unsteady flow and the following steady flow. The former is composed of drift wood only and the latter of two-layer flow of sediment-water mixture in the lower part and of wood-sediment-water mixture in the upper part. The numerical simulation indicates the peak flow discharge Q=92m³/s and peak sediment concentration C= 0.2 along the river valley. The volume of sediment runoff is estimated about 59,000m³ and this result agrees with the field survey.