Abstract
Abstract. Lahars are erosive floods, mixtures of water and pyroclastic detritus, known for being the biggest environmental disaster and causing a large number of fatalities in volcanic areas. Safety measures have been recently adopted in the threatened territories by constructing retaining dams and embankments in key positions. More disastrous events could be generated by the difficulty of maintaining these works in efficiency and for the changed risk conditions originating from their presence and the effects of their functioning. LLUNPIY/3r, a version of the cellular-automaton model LLUNPIY for lahar simulations, is presented. The growing frequency of lahars in the Vascún valley of Tungurahua volcano (Ecuador), probably due to the effects of the climatic change, has recently produced smaller and less dangerous events, sometimes favored by the collapse of ponds generated by small landslides. An investigation is performed here in order to reproduce such situations in a controlled way by the use of LLUNPIY/3r simulations. Using precise field data, points are individuated where dams by backfill, which are easy to collapse, can produce the formation of ponds; LLUNPIY/3r simulations permit projecting the triggering of small lahars by minor rainfall events or projecting, in the case of more rainfall, the anticipation of lahar detachment, avoiding simultaneous and dangerous confluence with other lahars.
Highlights
1.1 The problem of the laharsLahars are one of the most devastating phenomena in terms of the number of fatalities they cause in volcanic areas (Neall, 1976; Waythomas, 2014)
Physical parameters concern physical quantities that are used in equations of the transition function and correspond to values adopted in the implementation of the model or values as the temporal correspondence of a CA step pt, which must account for the fact that pa/pt > vmx, where vmx is the maximum possible velocity of flows during the development of the phenomenon
Our case study starts from examination of some significant natural events in the Vascún valley, an area that is heavily exposed to lahar risk
Summary
Lahars are one of the most devastating phenomena in terms of the number of fatalities they cause in volcanic areas (Neall, 1976; Waythomas, 2014) They are flows other than the common stream flow and consist of pyroclastic deposits mixed with water. Their physical properties (density, viscosity, and consistency) are very similar to wet concrete that has not yet hardened (Vallance, 2000). Lupiano et al.: Risk mitigation of lahars by a cellular-automata methodology: a case study (Pierson et al, 1990) Another case could occur when a large quantity of water is available from the breakout of a natural lake because of eruption (Manville, 2010). In many issues regarding complex systems, research was able to progress thanks to computer simulations, which allowed for developing multidisciplinary and transdisciplinary approaches, linked in part to the emergence of alternative computing paradigms, such as CA (Toffoli, 1984; Chopard and Droz, 1998; Iovine et al, 2007)
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