Depthwise dependence in the slowing behaviour of debris flows #

Daniel Mckinnell, Chris Johnson, Nico Gray

10:50 Wednesday in 4Q07.

Part of the Granular and multiphase flows session.

Abstract #

Debris flows occur when particles of rock surrounded by water flow downhill. These flows originate on steep mountainous slopes but flow onto the shallower slopes of valley floors. High fluid pressures support much of the solid weight, which decreases friction and prolongs the flow, compared to flows without interstitial fluid. As the fluid pressure dissipates, the material deposits from the base up. Previous continuum models have taken a depth averaged approach which simplifies the problem but makes assumptions about velocity and pressure profiles in the depthwise direction, and is unable to describe the gradual deposition of material. We will present a 1-D model that includes variation throughout the flow height, identify timescales present in slowing and compare to previous depth averaged models.