Triangular avalanches and uphill instabilities

TL;DR

This paper investigates the behavior of avalanches on inclined surfaces, revealing a transition from downward to upward propagation at a critical angle, explained through an extended phenomenological model.

Contribution

It introduces a simple interpretation of triangular avalanche propagation and uphill instabilities based on an extended surface flow model.

Findings

Avalanches form triangular regions with a specific opening angle.

A critical inclination causes avalanches to propagate uphill.

The model explains the transition at the critical angle.

Abstract

Recent experiments show that an avalanche initiated from a point source propagates downwards by invading a triangular shaped region. The opening angle of this triangle appears to reach 180$^o$ for a critical inclination of the pile, beyond which avalanches also propage upwards. We propose a simple interpretation of these observations, based on an extension of a phenomenological model for surface flows.