混合粒径材料からなる土石流扇状地の形成とその侵食

Abstract

A numerical simulation method which is consisted of the predictions of the debris flow development, the debris fan formation and the erosion of the debris fan by a flood flow is presented.The subsystem for the debris flow development renders possible to predict the hydrograph, the temporal variations in the solids concentration and the mean particle diameters of the debris flow that is induced by the appearance of the surface water flow on the gully bed composed of a well graded sediment mixture.This subsystem is verified by laboratory experiments and the effect of the accumulation of the largest particles in the forefront part is discussed.The subsystem for the debris fan formation process not only predicts the limit of deposition and the topography of the fan but also predicts the three-dimensional spatial distribution of the particle sizes in the debris fan. This particle size distributions are considered in the subsystem for the erosion of the fan and the re-deposition processes.