Gravity-driven mass flows

Gravity-driven mass flows, also known as sediment gravity flows, include a spectrum of phenomena in which more-or-less coherent mixtures of grains and intergranular fluid flow down slopes. At one end of this spectrum are dilute flows in which momentum is transferred mostly by fluid forces and sediment is largely a passive cargo that increases the effective fluid density. These dilute mass flows are part of a larger class of fluid dynamical phenomena known as gravity currents (Simpson, 1987; Bonnecaze et al., 1993). At the other end of the spectrum are concentrated mass flows such as granular avalanches and debris flows. Forces exerted by interacting solid grains dominate momentum transfer in such flows, although fluid forces can mediate grain interactions (Savage and Hutter, 1989; Iverson, 1997).