SURFACE FLOWS SIMULATION BY CELLULAR AUTOMATA: A SHORT REVIEW OF THE LLUNPIY MODEL

Abstract

Lahars represent one of the most destructive natural disasters regarding the loss of human lives, but also for making havoc on public infrastructures and ecological habitats. They are very complex surface flows subdivided into two main categories, primary and secondary lahars. Primary lahars are those that originated directly from eruptive volcanic activity, as in the tremendous 1985 Colombian event of Nevado del Ruiz. In contrast, secondary lahars may occur in post-eruptive events or quiescent periods. This volcanic debris flow, a mixture of water and pyroclastic sediments with high density and viscosity, under steep-slope conditions, is capable of reaching high speeds and can travel great distances. A variety of approaches have been adopted to model the behavior of lahar and to predict the hazards posed to downstream communities: empirical models developed, accounting mainly for some macro-observable phenomena, simple rheological and hydrological models that assume reasonable simplifications as a composition-independent flow behavior or a Newtonian flow regime, partial differential equations (PDE) which approximately describe the lahars, highly complex physics and hydrodynamics, and the Cellular Automata alternative methodology. Cellular Automata are a parallel computational paradigm for modeling complex systems by defining simple laws at a local level that generate a global complex evolution. The research, reported in this book, adopts a Multicomponent (or Macroscopic) Cellular Automata (MCA) approach that was developed for numerical simulation purposes by an interdisciplinary research group in Italy. Its reliability and validation on various past events, related to both primary and secondary lahars and debris flow catastrophic events, produced many significant scientific results.