ABSTRACT
Landslides, rockfalls, debris flows, and snow avalanches constitute natural hazards that can infer serious damages regarding human lifes, environment and economy (Hutter, 1996). Although considerable efforts have been devoted for years to the studies of geological surge flows, underlying mechanisms remain ill-understood. Here, we limit ourself on the avalanche properties of a model system constituted of dry cohesiveless particles. Such model systems can manifest different types of flows, according to the magnitude of the supply flux. For a large flux, the flow appears to be continuous, in opposition to the regime of weak supply flux for which the flow displays a series of discrete avalanches. The existence of these two different regimes originates in the requirement for the free surface slope to overpass a certain angle θstart to initiate the flow. If the spontaneous discharge rate of the surface flow is not balanced by the uphill supply flux, the slope progressively decreases and the flow stops at angle θstop. Then a new avalanche is generated after the delay time required to store enough matter and to increase again the slope up to the angle θstart On the contrary, if the supply flux is larger than the natural discharge rate of one avalanche, the continuous flow regime is encountered (Rajchenbach, 1990).
