Surge dynamics coupled to pore-pressure evolution in debris flows

Temporally and spatially varying pore-fluid pressures exert strong controls oil debris-flow motion by mediating internal and basal friction. at grain contacts. We analyze these effects by deriving a one-dimensional model of pore-pressure diffusion explicitly coupled to changes in debris-flow thickness. The now pore-pressure equation is combined with Iverson's (1997) extension of the depth-averaged Savage-Hutter (1989, 1991) granular avalanche equations to predict motion of unsteady debris-flow surges with evolving poreo-pressure distributions. Computational results illustrate the profound effects of pore-pressure diffusivities on debris-flow surge depths and velocities.