DEBRIS FLOW MODELING - A REVIEW

A debris flow represents a mixture of sediment particles of various si zes and water flowing down a confined, channel-shaped region (e.g., gu lly, ravine or valley) down to its end, at which point it becomes unco nfined and spreads out into a fan-shaped mass. This review begins with a survey of the literature on the physical-mathematical modeling of d ebris flows. Next, we discuss the basic aspects of their phenomenology , such as dilatancy, internal friction, fluidization, and particle seg regation. The basic characterization of a debris flow as a mixture mot ivates the application of the continuum thermodynamical theory of mixt ures to formulate a model for a debris flow as a viscous fluid-granula r solid mixture. A major advantage of such a formulation, which goes b eyond the most general models in the literature, e.g., Takahashi (1991 ), is that it can be used to expose and better understand the assumpti ons underlying existing models, as well as to derive new, more sophist icated models. Finally, we delve into the issue of how such models hav e been or can be implemented numerically, as well as general boundary conditions for debris flows.