合流部における土石流の挙動と変形

Abstract

Because the junction of the stream channels in a basin is the most evidentchange in the boundary conditions for a debris flow on its way to run out to thedebouchment; the behavior and the hydrograph may change drastically there. Somecharacteristic behaviors and the methods to predict them at the junction area arediscussed in this paper. First, a system of equations to predict the locus oftravelling of the tributary debris flow front in the main channel with or withoutstream flow is presented and compared to the experimental data. Second, thebehaviors of the debris flows at junction area are classified to the categories; thatstops and deposits within the area (Type 1), that leaves some deposits andcontinues to run down (Type 2) and that passes through without any deposition(Type 3). The conditions to identify each type are given and the debris damformation is suggested. Third, for the Type 1 deposition a simple method to knowthe shape of debris cone which will be formed at the junction is proposed. Finally, for the case of Type 2 and 3 the method to calculate the deformation ofhydrograph via the junction area is presented and compared with the experimentallyobtained hydrograph.