Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/nhess-2017-20
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
16 Jan 2017
Review status
This discussion paper is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Interactions between the accumulation of sediment storage and debris flow characteristics in a debris-flow initiation zone, Ohya landslide body, Japan
Fumitoshi Imaizumi1, Yuichi S. Hayakawa2, Norifumi Hotta3, Haruka Tsunetaka4, Okihiro Ohsaka1, and Satoshi Tsuchiya1 1Faculty of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan
2Centre for Spatial Information Science, The University of Tokyo, Kashiwa, 277-0871, Japan
3Faculty of Life and Environmental sciences, University of Tsukuba, Tsukuba, 305-8572, Japan
4Graduate School of Life and Environmental sciences, University of Tsukuba, Tsukuba, 305-8572, Japan
Abstract. Debris flows often occur in steep mountain channels, and can be extremely hazardous as a result of their destructive power, long travel distance, and high velocity. However, their characteristics in the initiation zones, which could possibly be affected by temporal changes in the channel topography associated with sediment supply from hillslopes and the evacuation of sediment by debris flows, are poorly understood. Thus, we studied the interaction between the flow characteristics and the topography in an initiation zone of debris flow at the Ohya landslide body in Japan using a variety of methods, including a physical analysis, a periodical terrestrial laser scanning (TLS) survey, and field monitoring. Our study clarified that both partly and fully saturated debris flows are important hydrogeomorphic processes in the initiation zones of debris flow because of the steep terrain. The predominant type of flow varied temporally and was affected by the volume of storage and rainfall patterns. The small-scale channel gradient (on the order of meters) formed by debris flows differed between the predominant flow types during debris flow events. The relationship between flow type and the slope gradient could be explained by a simple analysis of the static force at the bottom of the sediment mass.

Citation: Imaizumi, F., Hayakawa, Y. S., Hotta, N., Tsunetaka, H., Ohsaka, O., and Tsuchiya, S.: Interactions between the accumulation of sediment storage and debris flow characteristics in a debris-flow initiation zone, Ohya landslide body, Japan, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2017-20, in review, 2017.
Fumitoshi Imaizumi et al.
Fumitoshi Imaizumi et al.
Fumitoshi Imaizumi et al.

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