Experimental study on the effects of local sediment accumulation on a debris flow surge in a steep channel

Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga, Shizuoka 422-8529, Japan

^* Corresponding author: takayama.shoki@shizuoka.ac.jp

Abstract

Debris flow surges can terminate in a steep channel of > 15°. However, the termination process and mechanisms remain unknown. This study conducted small-scale flume experiments to investigate the effects of local sediment accumulation on debris-flow surges in a steep channel. The experiments demonstrated that local accumulation of bed sediment terminates a debris flow surge owing to abrupt changes in bed gradients and infiltration of debris flow interstitial water. Subsequently, the mass of the terminated debris-flow surge and bed sediment began to move, triggering a larger debris-flow surge. This result suggests that predicting the scale of a debris flow arriving downstream requires measuring the distribution of bed sediment in the debris flow initiation zone.