Debris flow is composed of mixed]size gravel, and the grain size distribution and concentration of sediment strongly affects the flow behavior. To predict more accurate debris flows, we need a numerical model that considers mixed]size gravel and can describe sediment sorting. We propose a more accurate method for predicting mixed]size debris flow behavior, from torrents to alluvial fans. We combined a debris flow model that can describe sediment sorting with an integration model, and proposed an integrated model for mixed]size gravel. Applying this model, we simulated debris flow on a virtual watershed under different conditions of inflow sediment distribution. Our results showed that an integrated model for mixed]size gravel provide a more rational description of debris flow in torrents and alluvial fans than models of uniform]sized gravel.

Key wordsFdebris flow, numerical simulation, size segregation, change of distribution, 1] and 2]dimensional integration model