Debris flow carries huge amount of sediment, from clay finer than 10-3 mm to huge stonesof several meters in diameter. Clay, sand, gravels and boulders move in different mechanisms.Field investigations performed by the authors reveal that there are two kinds of debris flowswith different mechanismst viscous debris now and two-phase debris flow. viscous debrisflow consists of more fine material and exhibits intermittent flow, paving way process, dragreduction and high superelevation. Drag reduction is caused by the paving way process andaeration of the flowing mixture. Two-phase debris flow consists mainly of coarse materialand exhibits steep stone front, stone street, inverse grading and higher resistance.Investigation on the slope of debris flow gullies shows that the coarser the debris material thehigher the slope of the gullies.
