Author(s): Hiroyuki Nagano; Haruyuki Hashimoto; Tomohiro Miyoshi
Linked Author(s):
Keywords: Debris flow; Woody debris; Wood-sediment-water mixture flow; Numerical simulation; Landslide
Abstract: Debris flows induced by landslides often run down from the mountain areas to the downstream areas with a large amount of woody debris. Woody debris accumulates at flow front during their moving down the rivers and hit houses at residential areas. Sometimes woody pieces are trapped by piers at bridges and cause overflowing. Therefore, the estimation of outflow of debris flows with woody debris becomes important for disaster prevention. In this paper, we propose a one-dimensional model of landslide-induced debris flow with a large amount of woody debris. In this model, the flow structure consists of the front and the following parts. The former part has only woody debris, while the latter part is sediment-water mixture flow with woody debris on the surface. Therefore, the latter part has two layers; the major one is sediment-water mixture flow and the upper surface one is woody debris. We apply this model to the landslide-induced debris flow which occurred at Hachimandani River in Hofu City, Japan on July 21, 2009. The numerical results show that the woody debris at the flow front increases in the scale and the arriving time of woody debris peak discharge to the downstream end is shorter than that of sediment discharge. The simulation results calculated in this study agreement with the results estimated from the field investigation.
Year: 2013