Comparison of avulsion cycles from subaerial and subaqueous fan experiments with supercritical channels

A series of alluvial fan experiments was compared to a series of submarine fan experiments in order to explore the similarities and differences of autogenic supercritical avulsion cycles in the two environments. Both systems have cycles of: distributive channel formation and basinward extension, deceleration and mouth bar deposition, flow interaction with the aggrading mouth bar, propagation of the channel-to-lobe transition in the upstream direction, and flow reorganization. The channel-to-lobe transition in both alluvial fan and submarine fan experiments was located at the supercritical-to-subcritical flow transition. Channel-to-lobe transitions were also the primary locus of deposition in each case, and their aggradation in turn forced upstream accretion. The commonalities between the two environments are striking and lend evidence toward the hypothesis that supercritical vs. subcritical flow in distributary channels is a more significant distinction than subaerial vs. subaqueous environment in terms of the hydraulic and sediment transport properties.