A modelling approach with Macroscopic Cellular Automata for hazard zonation of debris flows and lahars by computer simulations.

Cellular Automata (CA) represent both abstract dynamical systems evolving on the base of local interactions of their constituent parts and a parallel computational paradigm for modelling complex phenomena, whose evolution may be explicated mostly in terms of local rules. CA represent a powerful tool for simulating fluid-dynamical system; Macroscopic CA (MCA) characterize a methodological approach, which proved efficacious for modelling and simulating large scale surface flows. Fast-moving flow-like "landslides", as lahars, debris and mud flows, give rise to very destructive natural disasters as number of casualties in the world. Simulation of such phenomena could be an important tool for hazard management in threatened regions. This paper presents the modelling methodology of MCA for such a type of surface flows together with some models, based on this approach. They are SCIDDICA-SS2, SCIDDICA-SS3 (both for debris, mud and granular flows) and LLUNPIY (for primary and secondary lahars). Such models share certain features (common sub-states and elementary processes), while different specifications are introduced according to the peculiarities of related surface flows. Examples of simulations of both past (validation phase) and probable future events (developing hazard scenarios) are presented for each model. The last version of LLUNPIY is here introduced with new applications to lahar hazard related to Ecuador's volcanos Cotopaxi and Tungurahua.