FLOW CHARACTERISTICS OF WOOD-SEDIMENT-WATER MIXTURE IN THE SHIRAKIDANI RIVER, ASAKURA CITY, JAPAN IN 2017

Abstract

This paper describes the characteristics of the debris flow with woody debris which occurred in the Shirakidani River in Asakura City, Japan on July 5^th, 2017. 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 woody debris. This model considers two-layer flow; the lower layer expresses sediment-water mixture and the upper layer shows wood-sediment-water mixture. The numerical simulation indicates the peak flow discharge Q=70m³/s and peak sediment concentration C= 0.2 along the river valley. The sediment runoff volume is estimated about 160,000m³ and this result agrees with field survey.